JSES International 6 (2022) 604e614

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The responsiveness and validity of the Rotator Cuff Quality of Life
(RC-QOL) index in a 2-year follow-up study
Caitlin D. Richards, MSc, CAT(C)a, Breda H.F. Eubank, PhD, CAT(C)b,*,
Mark R. Lafave, PhD, CAT(C)c, J. Preston Wiley, MD, MPE, CCFP(SEM), FCFPd,
Aaron J. Bois, MD, MSc, FRCSCe, Nicholas G. Mohtadi, MD, MSc, FRCSCf
a

Lecturer, Department of Health & Physical Education, Faculty of Health, Community, and Education, Mount Royal University, Calgary, AB, Canada
Assistant Professor, Department of Health & Physical Education, Faculty of Health, Community, and Education, Mount Royal University, Calgary, AB,
Canada
c
Professor & Athletic Therapy Program Coordinator, Department of Health and Physical Education, Faculty of Health, Community, and Education, Mount
Royal University, Calgary, AB, Canada
d
Professor, Sport Medicine Centre, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
e
Clinical Assistant Professor, Division of Shoulder and Elbow Surgery, Section of Orthopaedic Surgery, Cumming School of Medicine, University of Calgary,
Calgary, AB, Canada
f
Clinical Professor, Department of Surgery, Cumming School of Medicine, Medical Director, Sport Medicine Centre, Faculty of Kinesiology, McCaig Institute
for Bone and Joint Health, University of Calgary, Calgary, AB, Canada
b

a r t i c l e i n f o
Keywords:
Shoulder
Psychometric assessment
Validity
Responsiveness
Reliability
Quality of life
Rotator cuff
Level of evidence: Basic Science Study;
Validation of Outcome Instruments

Background: The Rotator Cuff Quality of Life (RC-QOL) index was developed to evaluate quality of life in
patients with rotator cuff disease. This study provides additional psychometric testing in accordance with
the Consensus-Based Standards for the Selection of Health Measurement Instruments guidelines.
Methods: This was a 2-year follow-up study on 66 patients (mean age, 59 ± 10 years) originally presenting with chronic full-thickness rotator cuff tears to a tertiary care center. The methodology involved
testing internal consistency, content validity, and criterion validity. Responsiveness was evaluated using
3 strategies: 1) standardized response mean of the raw change scores; 2) Guyatt’s Responsiveness Index;
and 3) Global Rating Scales of improvement correlated to a quality of life measure.
Results: Content validity was conﬁrmed with a Cronbach a of 0.92 (95% conﬁdence interval, 0.92-0.95)
and absence of ﬂoor and ceiling effects. Criterion validity was conﬁrmed using the Western Ontario
Rotator Cuff Index as a reference standard (r ¼ 0.87, P < .001). The effect size of distribution-based
methods of determining responsiveness was large (0.99-1.09) compared to that of mixed- and anchorbased methods (0.47-0.89). All responsiveness calculations met minimum requirements for acceptable
thresholds.
Conclusion: The RC-QOL is a valid and responsive measure of health-related quality of life in patients
with chronic rotator cuff pathology. The results of this study added to the methodologic quality
assessment of the RC-QOL, completing 7 of 10 Consensus-Based Standards for the Selection of Health
Measurement Instruments criteria.
© 2022 The Author(s). Published by Elsevier Inc. on behalf of American Shoulder and Elbow Surgeons.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).

The Rotator Cuff Quality of Life (RC-QOL) index is a diseasespeciﬁc health-related patient-reported outcome measure (HRPROM) used in evaluating health status and quality of life for

This study was approved by the Conjoint Health Research Ethics Board at the
University of Calgary (REB 14-1828).
*Corresponding author: Breda H.F. Eubank, PhD, CAT(C), Department of Health
and Physical Education, Faculty of Health, Community, and Education, Mount Royal
University, 4825 Mount Royal Gate SW, Calgary, AB T3E 6K6, Canada.
E-mail address: beubank@mtroyal.ca (B.H.F. Eubank).

patients with the full spectrum of rotator cuff disease.14 Created in
English, this tool has completed cross-cultural validation when
translated into Italian, German, Turkish, Chinese, and Spanish.4,15,22,32 Eleven studies have evaluated the psychometric properties of the RC-QOL in the context of the Consensus-Based
Standards for the Selection of Health Measurement Instruments
(COSMIN) guidelines.3,4,8,14,15,22,23,26,29,30,32 The COSMIN guidelines
consist of 10 criteria that can be used to assess whether a study has
met the standards for good methodologic quality: internal consistency,
reliability
(ie,
test-retest,
interrater,
intrarater),

https://doi.org/10.1016/j.jseint.2022.04.012
2666-6383/© 2022 The Author(s). Published by Elsevier Inc. on behalf of American Shoulder and Elbow Surgeons. This is an open access article under the CC BY-NC-ND
license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

C.D. Richards, B.H.F. Eubank, M.R. Lafave et al.

JSES International 6 (2022) 604e614

measurement error, content validity, construct validity (ie, hypothesis testing), structural validity, criterion validity, crosscultural validity, responsiveness, and interpretability.24 The RCQOL has been evaluated on 7 of the COSMIN criteria.
Responsiveness of the RC-QOL has been assessed on 4 occasions
but only by using a distribution-based approach.3,8,23,29 HR-PROMs
must demonstrate responsiveness where scores are sensitive to
actual changes in health status. The estimation of the minimal
clinically important difference (MCID), which is also used to
determine the responsiveness of a tool, should be based on multiple strategies and triangulation of methods.31 Distribution-based
methods are derived from the statistical spread or variation of data
using standard deviation (SD), standard error of the measurement,
standardized response mean (SRM), and effect size (ES).28 Anchorbased methods use relevant patient-rated, clinician-rated, and
disease-speciﬁc variables that provide primary and meaningful
estimates of an instrument’s MCID.31 Anchor-based methods
compare changes in scores with an external marker as reference.28
Traditional external anchors vary between Likert-type scales and
visual analog scales (VAS). Research has shown that there is no
signiﬁcant difference in type of scales and little consensus on the
best mode of questioning when implementing external
anchors.11,16
The task of validating HR-PROMs is a continual process to
conﬁrm its value and use in research or clinical practice.38 The RCQOL should possess the full spectrum of recognized measurement
properties, need to be clearly demonstrated, and need to be
considered adequate. Therefore, the purpose of this study was is
to provide additional psychometric assessment of the RC-QOL in
the context of the COSMIN guidelines. This study will also evaluate responsiveness using 3 strategies: 1) SRM of the raw change
scores; 2) Guyatt’s Responsiveness Index (GRI); and 3) Global
Rating Scales (GRS) of improvement correlated to quality of life
measure.

Table I
Characteristics of study patients at baseline and the 2-year follow-up.
Category

Interval

Group

n

Mean (SD)

Age (yr)

Baseline
2 yr
Baseline

Overall
Overall
Nonsurgical
Surgical
Nonsurgical
Surgical
Overall
Overall
Nonsurgical
Surgical
Nonsurgical
Surgical

87
66
39
48
24
42
87
66
39
48
24
42

57 (10)
59 (10)
58 (12)
56 (8)
59 (11)
59 (10)
M: 60 (69%); F: 27 (31%)
M: 40 (62%); F: 26 (38%)
M: 28 (72%); F: 11 (28%)
M: 32 (67%); F: 16 (33%)
M: 13 (54%); F: 11 (46%)
M: 27 (64%); F: 15 (36%)

2 yr
Sex (% of N)

Baseline
2 yr
Baseline
2 yr

M, male; F, female; SD, standard deviation.

were also excluded if they were unable or unwilling to
complete the study or provide informed consent. Patients
completed Web-based versions of the RC-QOL,14 the Western
Ontario Rotator Cuff Questionnaire (WORC),17 and 2 GRS10,20
approximately 24 ± 6 months after their baseline questionnaire
was completed.
Instruments
Rotator Cuff Quality of Life index
The RC-QOL consists of 34 questions and 5 subscales: symptoms
and physical complaints (SYMPTOMS), 16 items; work-related
concerns (WORK), 4 items; recreational activities, sports participation, or competition concerns (SPORTS), 4 items; lifestyle concerns (LIFESTYLE), 5 items; and social and emotional concerns
(SOCIAL/EMOTIONAL), 5 items. Each question is scored on a 100mm VAS from 0 (most symptomatic) to 100 (asymptomatic). The
quality of life score is calculated by taking an average of items
answered by respondents. For example, if the patient answered all
34 items, 34 values are summed, divided by 3400, and multiplied
by 100. Patients are given the option of answering “not applicable”
to 14 questions. These responses are treated as if these items had
never been offered to the patient. If the patient answered “Not
applicable” to 14 questions, these responses are treated as missing
by design, and the sum of the remaining questions is divided by the
new denominator and then multiplied by 100 (ie, 2000/
[3400  1400]*100). A score of 0 reﬂects the worst quality of life
(most symptomatic), and a score of 100 reﬂects the best quality of
life (asymptomatic).

Methods
Study design
This study was approved by the Conjoint Health Research Ethics
Board at the University of Calgary. This study presents 2-year
follow-up data on a cohort of 87 patients that originally presented to a tertiary care clinic: the University of Calgary Sport
Medicine Centre.8,9 These patients were initially referred to 1 of 3
orthopedic surgeons at the University of Calgary Sport Medicine
Centre. Patients were identiﬁed from new and follow-up referrals
from primary care physicians. Both nonsurgical and surgical patients were targeted. Following a surgical consultation, patients in
the nonsurgical group were deemed to not require immediate
surgical management and were treated with an evidence-based
nonoperative program. Surgical patients had conﬁrmed surgical
dates or had already received surgical management for their
shoulder problem. These 2 groups were chosen as a representative
sample of patients with chronic rotator cuff tears currently presenting to point of care. Patients who a priori consented for future
research were contacted and provided consent again for the 2-year
study.
Inclusion criteria consisted of English-speaking and literate
patients aged older than 18 years. Patients were included if they
presented with a chronic full-thickness rotator cuff tear conﬁrmed
by ultrasonography or magnetic resonance imaging. Patients were
excluded if they presented with concomitant symptomatic pathology of the affected shoulder (ie, instability, osteoarthritis);
signiﬁcant cervical spine pathology or radiculopathy or both; or
gain issues (ie, workers’ compensation or litigation). Individuals

Western Ontario Rotator Cuff Questionnaire
The only other Canadian English-based rotator cuff-speciﬁc
PROM, the WORC, consists of 21 items representing 5 domains
each with a 100-mm VAS response option. The 5 domains include
physical symptoms (SYMPTOMS), 6 items; sports and recreation
(SPORTS), 4 items; work (WORK), 4 items; lifestyle (LIFESTYLE), 4
items; and emotions (SOCIAL/EMTIONAL), 3 items. Each question is
also scored on a 100-point VAS but with reversed interpretations
where “0” indicates asymptomatic and “100” indicates most
symptomatic. The maximum possible score is 2100, meaning worst
possible symptoms, and the best or asymptomatic score is 0. The
WORC does not have any “Not-applicable” options. For a more
clinical friendly interpretation, this study reported the WORC score
as a percentage by subtracting the total score from 2100, dividing
by 2100, and multiplying by 100. This allows for ease of comparison
to the RC-QOL and also for similar interpretations where 0% indicates the lowest functional status level and 100% indicates the
highest functional status level.
605

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JSES International 6 (2022) 604e614

Table II
Baseline and 2-year follow-up scores of the RC-QOL index and WORC.
Category

Interval

RC-QOL (yr)

Baseline
2 yr
Baseline

Group
Overall
Loss to follow-up patients removed
Overall
Overall
Loss to follow-up patients removed

2 yr

Overall

WORC score

2 yr
2 yr

RC-QOL change score (raw)

2 yr
2 yr

Overall
Nonsurgical
Surgical
Overall
Nonsurgical
Surgical

Nonsurgical
Surgical
Nonsurgical
Surgical
Nonsurgical
Surgical

n

Mean (SD)

87
66
66
39
48
24
42
24
42
66
24
42
66
24
42

49 (22)
47 (22)
74 (24)
47 (20)
50 (23)
56 (19)
42 (22)
77 (20)
73 (25)
73 (23)
75 (21)
71 (25)
27 (28)
21 (24)
31 (42)

P value
.001
.386
.389
.494
<.001

RC-QOL, Rotator Cuff Quality of Life; SD, standard deviation; WORC, Western Ontario Rotator Cuff.

raw change score (xpost  xpre Þ.28 These calculations were
completed using Equation 1:
Equation 1. SRM equation for calculating important difference.2

Global Rating Scales
Two GRS were used as anchor-based methods to evaluate the
responsiveness of symptoms and function: A 7-point GRS was
adapted from the study by Greco et al,10 and a VAS GRS was adapted
from the study by Lafave et al20 ranging from 100 (signiﬁcantly
worse) to þ100 points (signiﬁcantly improved).

SRMraw ¼

xpost  xpre
schange

1

Reliability
Guyatt’s Responsiveness Index
GRI is a distribution-based method requiring an anchor-based
MCID using the smallest difference between baseline and posttest stage representing the meaningful change in a group using a
7-point VAS GRS.18,21 This use of an external anchor in combination
with the statistical spread of the data provides a mixed approach to
responsiveness. Patients reported “Somewhat worse” or “Somewhat better” on the 7-point GRS. In the absence of an external
anchor, or for comparative purposes, MCID was calculated using the
distribution-based approach using the mean change scores.18 The
GRI was calculated using both mixed (GRIMixed) and distributionbased (GRIDistribution) methods, whereby MSE is the mean squared
error of the response obtained from an analysis of variance model
that examines repeated observations of the measure in clinically
stable subjects.12 These calculations were completed using Equation 2:
Equation 2. Guyatt’s Responsiveness Index equation for calculating important difference.12

To assess the homogeneity of items, internal consistency was
measured using Cronbach’s alpha (a) calculations. Internal consistency was examined for both the overall RC-QOL and WORC and
each subscale. The questions in each subscale were analyzed to
determine the degree to which they ﬁt into that subscale (SYMPTOM, WORK, SPORTS/RECREATION, LIFESTYLE, and SOCIAL/
EMOTIONAL).28
Content validity
Floor and ceiling effects were calculated to assess content validity. Floor and ceiling effects were calculated at 15%, 20%, 25%, and
30% stratiﬁcations using the RC-QOL at baseline and RC-QOL and
WORC at the 2-year follow-up interval.
Criterion validity
Criterion validity was measured by means of concurrent validity.
The RC-QOL was correlated to the WORC at the 2-year time interval
(24 ± 6 months). A nonparametric Spearman rank correlation test
(rS) and Lin’s concordance correlation coefﬁcient (rc) were used to
compare the mean scores of the RC-QOL and the WORC.

MCID
GRI ¼ pﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ
2*MSE

Responsiveness

2

GRS correlation
GRS correlation is an anchor-based method of determining
responsiveness and compares changes in scores with an external
marker as reference.18,27 This external marker compares a secondary response by patients to indicate their perceived level of
change. A correlation coefﬁcient was used to determine the relationship between the mean change score in the RC-QOL between
the baseline and 24-month scores with a 7-point GRS and again
with a VAS GRS.20 Values of 0.2, 0.5, and 0.8 were used to represent
small, moderate, and large effects, respectively.39 The SRMraw16,25
was restricted to patients who experienced change and was
calculated as the ratio of the mean raw change score to the SD of
that raw change score. The change group was deﬁned as patients
who were included in the extremes of the 7-point GRS. These

Responsiveness was determined using 3 strategies: 1) SRM of
the raw change scores (SRMraw; distribution-based method); 2)
GRI (distribution-based method requiring anchor-based MCID);
and 3) GRS of improvement correlated to a quality of life measure
(anchor-based method).16
Standardized response mean
The SRM is the ratio of individual change to the SD of that
change.6 A large SRM indicates that the change is large relative to
the background variability in the measurements.6 The SRMraw was
restricted to patients who experienced change and was calculated
as the ratio of the mean raw change score (schange Þ to the SD of that
606

C.D. Richards, B.H.F. Eubank, M.R. Lafave et al.

JSES International 6 (2022) 604e614

Figure 1 Median Rotator Cuff Quality of Life (RC-QOL) index scores at baseline (n ¼ 87), 2-year follow-up interval (n ¼ 66), as well as change score between time intervals (n ¼ 66).

Statistical analysis

Table III
Cronbach’s a of the RC-QOL index (baseline and 2-yr follow-up) (n ¼ 87) and WORC
(2-yr follow-up) (n ¼ 63).
Domain

Cronbach’s a (n)a

Cronbach a
Nonsurgical (n)

Surgical (n)

RC-QOL (baseline)
SYMPTOM
WORK
SPORTS
LIFESTYLE
SOCIAL/EMOTIONAL
RC-QOL (2 yr)
SYMPTOM
WORK
SPORTS
LIFESTYLE
SOCIAL/EMOTIONAL
WORC (2 yr)
SYMPTOM
WORK
SPORTS
LIFESTYLE
EMOTIONAL

0.919 (87)
0.922 (87)
0.920 (87)
0.920 (87)
0.918 (87)
0.922 (87)
0.911 (63)
0.913 (63)
0.914 (39)
0.916 (63)
0.910 (63)
0.915 (63)
0.910 (63)
0.932 (63)
0.930 (63)
0.938 (63)
0.932 (63)
0.943 (63)

0.937 (39)
0.937 (39)
0.945 (39)
0.940 (39)
0.937 (39)
0.933 (39)
0.932 (27)
0.933 (27)
0.940 (16)
0.936 (27)
0.932 (27)
0.936 (27)
0.932 (27)
0.934 (27)
0.932 (27)
0.934 (27)
0.933 (27)
0.935 (27)

0.929 (48)
0.932 (48)
0.928 (48)
0.929 (48)
0.927 (48)
0.932 (48)
0.920 (36)
0.923 (36)
0.926 (23)
0.923 (36)
0.919 (36)
0.924 (36)
0.920 (36)
0.923 (36)
0.922 (36)
0.922 (36)
0.925 (36)
0.925 (36)

Data analyses were computed using Stata Statistical Software:
Release 14 (StataCorp., College Station, TX, USA),34 and statistical
signiﬁcance was accepted at the P < .05 level. All primary analyses
were subsequently stratiﬁed based on surgical status. Independent
t-tests were used to compare homogeneity of variance in age, sex,
and RC-QOL scores between nonsurgical and surgical patients at
baseline and 2-year time intervals. A paired t-test was also used to
detect signiﬁcant changes in patients’ RC-QOL scores between
baseline and the 2-year time interval.

Results
Eighty-seven patients were entered in the study at baseline (60
males, 27 females) with a mean age of 57 years (range, 27-78 years).
Sixty-six patients (40 males and 26 females) participated at the 2year follow-up interval with a mean age of 59 years (range, 29-80
years). At the 2-year interval, no patients declined participation,
and 21 patients (24%) were lost to follow-up. Researchers were
unable to contact 12 patients, and 9 did not return questionnaires
within the allotted timeframe (24 ± 6 months). The median timeframe for completing follow-up questionnaires was 27 months
following baseline (SD, 2; range, 22-30 months).
Table I presents baseline and 2-year follow-up demographic
data. Age and sex were not statistically different between baseline
and 2-year follow-up samples (P ¼ .778 and P ¼ .783, respectively)
or between the surgical and nonsurgical groups at baseline (P ¼ .147
and P ¼ .137, respectively) and at 2-year follow-up (P ¼ .160 and
P ¼ .204, respectively). Table II presents baseline and 2-year followup RC-QOL scores, RC-QOL change, and WORC scores. Mean RC-QOL
scores at baseline (P ¼ .389) and at the 2-year follow-up (P ¼ .494)
were not statistically different between the nonsurgical and surgical groups. However, there was a signiﬁcant change in RC-QOL
scores from baseline to 2 years (mean þ 27; SD, 28; P < .001).
Median RC-QOL scores at baseline and at the 2-year follow-up and

RC-QOL, Rotator Cuff Quality of Life; WORC, Western Ontario Rotator Cuff.

patients reported either “Very much worse” or “Very much better”
on the scale. Similar to the study by Beninato et al,2 patients that
reported “A little worse”, “No change”, and “A little bit better” were
considered “Unchanged” or “Stable”, in that there would be no
reported change by the patient or the change would be perceived as
little to none in these cases. In calculating the MCID, patients that
reported “Somewhat worse” or “Somewhat better” were deﬁned as
those patients who reported the smallest detectable change. Those
categories were the next available point above or below responses
that were considered stable. The MCID was determined by the
smallest absolute change scores in patients that perceived
change.37 Variation of data was calculated using a 1-way analysis of
variance of change scores in patients reporting little to no
change.18,21

607

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JSES International 6 (2022) 604e614

Table IV
Floor and ceiling effects of the RC-QOL index and WORC in up to 94 patients at baseline and 2-yr intervals.
Domain

Overall
SYMPTOM
WORK
SPORTS
LIFESTYLE
SOCIAL/EMOTIONAL

RC-QOL (baseline)

RC-QOL (2-yr)

WORC (2-yr)

Floor effect (%)

Ceiling effect (%)

Floor effect (%)

Ceiling effect (%)

Floor effect (%)

Ceiling effect (%)

0.0
1.1
6.4
5.3
0.0
0.0

0.0
1.1
0.0
1.1
1.1
3.2

0.0
0.0
0.0
0.0
0.0
0.0

3.2
4.8
0.0
9.5
6.3
14.3

0.0
0.0
0.0
0.0
1.6
1.6

6.3
6.3
9.5
4.8
11.1
19.0

RC-QOL, Rotator Cuff Quality of Life; WORC, Western Ontario Rotator Cuff.

Table V
Floor and ceiling effects of the RC-QOL index at baseline and the RC-QOL and WORC index at the 2-yr follow-up interval in up to 36 surgical and up to 27 nonsurgical patients
with rotator cuff disease.
RC-QOL (baseline)
Domain

Overall
SYMPTOM
WORK
SPORTS
LIFESTYLE
SOCIAL/EMOTIONAL

RC-QOL (2-yr)

WORC (2-yr)

Nonsurgical
(% of n ¼ 27)

Surgical
(% of n ¼ 36)

Nonsurgical
(% of n ¼ 27)

Surgical
(% of n ¼ 36)

Nonsurgical
(% of n ¼ 27)

Surgical
(% of n ¼ 36)

Floor

Ceiling

Floor

Ceiling

Floor

Ceiling

Floor

Ceiling

Floor

Ceiling

Floor

Ceiling

0.0
0.0
11.1
7.4
0.0
0.0

0.0
3.7
0.0
3.7
3.7
11.1

0.0
0.0
8.3
8.3
0.0
0.0

0.0
2.8
0.0
0.0
0.0
0.0

0.0
0.0
0.0
0.0
0.0
0.0

3.7
3.7
0.0
7.4
7.4
14.8

0.0
0.0
0.0
0.0
0.0
0.0

2.8
5.6
0.0
11.1
5.6
13.9

0.0
0.0
0.0
0.0
0.0
0.0

0.7
0.0
11.1
11.1
11.1
18.5

0.0
0.0
0.0
0.0
2.8
2.8

5.6
2.8
8.3
5.6
11.1
19.4

RC-QOL, Rotator Cuff Quality of Life; WORC, Western Ontario Rotator Cuff.

this only improved by þ1 point on the RC-QOL between time
points. This change score of 1 point is unlikely to be clinically
relevant if the patient is reporting notable differences on 2 separate
GRS. All outliers were excluded from the reliability analysis.

change score between the 2 intervals are visually represented in
Figure 1.
Reliability
Table III presents the Cronbach’s a of the RC-QOL at baseline and
the RC-QOL and WORC at the 2-year interval, stratiﬁed by surgical
status. At the 2-year interval, 24 patients reported work-related
questions as not applicable, thus decreasing the sample size for
calculating a to 39 patients for this speciﬁc domain. The Cronbach’s
a for the RC-QOL ranged from 0.918 to 0.922 at baseline and 0.910
to 0.916 at the 2-year interval. After stratifying by surgical status
at the 2-year mark, the sample sizes dropped to 16 nonsurgical
and 23 surgical patients. The Cronbach’s a for the baseline
nonsurgical cohort ranged from 0.933 to 0.945, and that for the
surgical cohort ranged from 0.927 to 0.932 with similar values at
the 2-year mark. These ranges are similar to the WORC at the 2-year
interval (0.910-0.943). The similarities in comparing baseline and
follow-up scores suggests unidimensionality of scales in the RCQOL and WORC (ie, all items measure the same construct to the
same extent).
Three outliers were identiﬁed in the 66-patient 2-year followup cohort. One outlier was a patient that completed questionnaires at 1 month postoperatively. It has been shown that change
reported from 0-3 months postoperatively in patients that have
undergone rotator cuff repairs is not statistically signiﬁcant in
groups similar to those in this study when using the RC-QOL.14 This
patient report is unlikely to represent true change in quality of life
status. The second outlier was a patient that reported a change
score of þ60 points on the RC-QOL while reporting no change on
both the 7-point GRS and VAS GRS. A change score as substantial as
60 points out of a possible 100 points should be expected to have a
similar response in both GRS. The third patient reported “Somewhat better” on the 7-point GRS and þ90 on the VAS GRS; however,

Content validity
Floor and ceiling effects were calculated to further determine
content validity of the RC-QOL and WORC (Table IV) and to further
determine content validity of the RC-QOL and WORC for nonsurgical and surgical groups (Table V). There were no ﬂoor or ceiling
effects in the RC-QOL at baseline or at the 2-year follow-up interval
and when stratiﬁed by surgical status. There is evidence of ceiling
effects (>15%) in both nonsurgical and surgical patients using the
WORC within the SOCIAL/EMOTIONAL domain.
Criterion/concurrent validity
The relationship between the RC-QOL and WORC scores at
the 2-year time interval is visually represented in Figure 2. The
Shapiro-Wilk W test denied the normality of the study data as the
RC-QOL and WORC tested at 0.88 (P < .001) and 0.92 (P < .001),
respectively. Therefore, the nonparametric Spearman rank correlation test (rS) and Lin’s concordance correlation coefﬁcient (rc)
were used to compare the RC-QOL and WORC scores. All tests
showed a similar strong correlation between scores at the 2-year
interval (0.88, P < .001) (Table VI).
Responsiveness
A summary of change scores for the domains of RC-QOL is
provided in Table VII. Mean change scores were consistently higher
in all domains for surgical patients when comparing to nonsurgical
patients.

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Figure 2 Rotator Cuff Quality of Life (RC-QOL) index scores correlated to Western Ontario Rotator Cuff (WORC) index scores in 63 patients with conﬁrmed rotator cuff disease at 2year follow-up interval.

cutoff points as in the primary analysis, GRIMixed was calculated
using an MCID of 13 points. This provided a GRI of 0.43, a small
effect.5 GRIDistribution was calculated using an MCID representing
mean change scores (26.85 points). GRIDistribution was calculated as
0.89, a large effect.5,39 The denominator representing the variation
of scores for stable patients was not statistically signiﬁcant (P < .41).

Table VI
Correlation of the RC-QOL index and WORC scores at the 2-yr interval using Pearson
and Spearman correlation coefﬁcients and Lin’s CCC.
Group

Correlation

RC-QOL vs. WORC

Overall (n ¼ 63)

Pearson r
Lin’s CCC rc
Spearman rs
Pearson r
Lin’s CCC rc
Spearman rs
Pearson r
Lin’s CCC rc

0.87 (P < .001)
0.87 (P < .001)
0.88 (P < .001)
0.92 (P < .001)
0.92 (P < .001)
0.80 (P < .001)
0.85 (P < .001)
0.80 (P < .001)

Nonsurgical (n ¼ 27)

Surgical (n ¼ 36)

GRS correlation
The Shapiro-Wilk W test conﬁrmed normal distribution of the
data (0.98, P < .49). Therefore, a correlation using Pearson r coefﬁcient calculation (Table IX) was completed between the 7-point
GRS and raw RC-QOL change scores (Fig. 3), as well as the VAS
GRS and the raw RC-QOL change scores (Fig. 4). The correlation
between the 7-point GRS and raw RC-QOL change scores is 0.44
(P < .001). This represents a positive modest relationship.28 The
correlation between the VAS GRS and raw RC-QOL change scores
was 0.42 (P < .0001). This also represents a positive modest
relationship.28
A correlation using Pearson r coefﬁcient calculation (Table IX)
was completed between the 7-point GRS and raw RC-QOL change
scores, as well as the VAS GRS and the raw RC-QOL change scores
for both surgical (Figs. 5 and 6, respectively) and nonsurgical patients (Figs. 7 and 8, respectively). The correlation between the 7point GRS and raw RC-QOL change scores was 0.45 (P < .01) for
surgical patients. This represents a positive modest relationship.28
The correlation between the VAS GRS and raw RC-QOL change
scores for surgical patients is 0.42 (P < .01). This represents a positive modest relationship.28 The correlation between the 7-point
GRS and raw RC-QOL change scores was 0.45 (P < .02) for
nonsurgical patients. This represents a positive modest relationship.28 The correlation between the VAS GRS and raw RC-QOL
change scores was 0.44 (P < .02). This also represents a positive
modest relationship.28

CCC, Concordance Correlation Coefﬁcient; RC-QOL, Rotator Cuff Quality of Life;
WORC, Western Ontario Rotator Cuff.

Standardized response mean
SRM was calculated to represent distribution-based methods
using SD of the sample (s). Calculations using 63 observations
provided an SRM of 0.99. This represents a large ES or large difference between baseline and 2-year follow-up scores.5 SRM was
calculated for both surgical (n ¼ 36) and nonsurgical groups
(n ¼ 27). Nonsurgical and surgical groups provided an SRM of 0.91
and 1.09, respectively, which represents a large ES.5
Guyatt’s Responsiveness Index
GRIMixed was calculated using an MCID of 13 points. This provided a GRI of 0.48, a small effect.5 GRIDistribution was calculated
using an MCID representing mean change scores (27.97 points).
GRIDistribution was calculated as 1.03, a large effect.5,39 The denominator representing the variation of scores for stable patients was
not statistically signiﬁcant (P < .49). The nature of the GRI requires
information on the spread of data in patients that are considered
“unchanged” or “stable.” Of the surgical patients at the 2-year interval, only 1 patient was reported as stable; therefore, variation in
data was not calculated, and the GRI for surgical patients could not
be determined. The GRI was recalculated for nonsurgical patients.
Using both mixed- and distribution-based methods, results for
nonsurgical patients are outlined in Table VIII. Using the same

Discussion
The purpose of this study was to provide additional methodological assessment of the RC-QOL. The RC-QOL was previously
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Table VII
Summary of absolute RC-QOL index change scores from baseline to 2-yr follow-up for patients with conﬁrmed rotator cuff tears.
Domain change score

Overall
Absolute mean change score
± SD (n)

Nonsurgical absolute mean change score
± SD (n)

Surgical
Absolute mean change score
± SD (n)

SYMPTOM
WORK
SPORT
LIFESTYLE
SOCIAL/EMOTIONAL
RC-QOL

34 ± 23 (63)
30 ± 21 (40)
20 ± 26 (63)
40 ± 25 (63)
25 ± 20 (63)
33 ± 21 (63)

25 ± 23 (28)
27 ± 17 (17)
32 ± 22 (28)
35 ± 22 (28)
20 ± 17 (28)
26 ± 18 (28)

40 ± 26 (36)
33 ± 24 (23)
47 ± 29 (36)
44 ± 27 (36)
30 ± 21 (36)
38 ± 23 (36)

RC-QOL, Rotator Cuff Quality of Life; SD, standard deviation.

correlations were found between the RC-QOL and the WORC using
the Spearman rank correlation and Lin’s concordance correlation
coefﬁcient, suggesting a similar relationshipd0.87, P < .001, and
.87, P < .001, respectively. In addition, when correlations were
assessed based on surgical status, correlations were stronger for
nonsurgical patients (0.88-0.92) than for surgical patients (0.80).
Both trends indicate that as WORC scores increase, RC-QOL scores
also increase. This provides additional methodological support for
criterion validity of the RC-QOL using the WORC as a reference
standard.
In the baseline study, responsiveness was only measured using
distribution-based approaches.8 In the 2-year follow-up study,
responsiveness was evaluated using both distribution and anchorbased methods. In comparing results, it is important to understand
the term ES. In quantitative research, the context of this study, ES is
often described as the magnitude of the difference between
groups.36 This contrasts with the absolute ES that was described
above as the mean change score. Absolute ES does not consider the
variability in scores, in that not every subject achieved the average
outcome.35 Cohen's term d is an example of this type of ES index.
Cohen classiﬁed ES as small (0.2), medium (0.5), and large (0.8).5
These categories, however, do not take into account other variables such as the accuracy of the HR-PROM nor the varying characteristics of the study population. The purpose of ES cutoffs simply
provides a general guideline for comparative purposes.
The SRM, as well as GRIDistribution, demonstrated a large ES of the
RC-QOL in all groups. SRM ranged from 0.91 to 1.09 among the 3
groups. The GRIDistribution was calculated as 0.89 in the overall
group, a large effect.5 Although the GRIDistribution score appears to be
more conservative, both calculations indicate that the RC-QOL was
able to detect a statistically large difference between baseline and
2-year follow-up scores using 2 different distribution-based
methods.
The RC-QOL using 2 external anchors, a 7-point Likert-style GRS
and a 100-mm VAS as the second GRS, showed positive modest
correlations for all groups.5 All correlations were statistically signiﬁcant. The low correlation of these tests in comparison to those of
the distribution-based methods does not indicate that the RC-QOL
demonstrates poor sensitivity to change, but rather that the
external anchor may not be able to capture the same snapshot of
quality of life in these patients.13,31 Revicki et al recommend 0.300.35 of Cohen's cutoff points of 0.30-0.35 as the minimum correlation threshold and acceptable association between an external
anchor and a HR-PROM change score.31 Using these guidelines, the
correlation to both external anchors exceeds the minimum
threshold for responsiveness.
The literature has indicated the usefulness of the mixed-method
calculations to conﬁrm MCID.1 These methods allow for external,
anchor-based information regarding change in conjunction with
sample variance, or statistical characteristics, to provide a responsiveness score. In the context of this study, GRIMixed provided scores
using anchor-based MCID of the RC-QOL and the variance of the

Table VIII
GRI calculations of the RC-QOL index using mixed- and distribution-based methods
in up to 63 patients with conﬁrmed rotator cuff disease.
Group (n)

GRI method

MCID

MSE of stable patients

GRI

Overall (63)

GRIMixed
GRIDistribution
GRIMixed
GRIDistribution

13
27.97
13
26.85

371.07 (P < .49)

0.48
1.03
0.43
0.89

Nonsurgical (27)

451.33 (P < .41)

GRI, Guyatt's Responsiveness Index; MCID, minimal clinically important difference;
MSE, mean squared error; RC-QOL, Rotator Cuff Quality of Life.
Table IX
Pearson Correlation of raw RC-QOL index change scores over a 2-yr period and the
7-point and VAS GRS.
Group (n)

GRS

Correlation

Overall (63)

7-Point
VAS
7-Point
VAS
7-Point
VAS

0.44 (P < .001)
0.42 (P < .0001)
0.45 (P < .02)
0.44 (P < .02)
0.45 (P < .0056)
0.42 (P < .0111)

Nonsurgical (27)
Surgical (36)

RC-QOL, Rotator Cuff Quality of Life; VAS GRS, visual analog global rating scales.

evaluated in 2015 using the criteria of the COSMIN guidelines.8 This
study evaluated the RC-QOL at the 2-year follow-up and provides
additional methodological support for reliability, validity, and
responsiveness.
Reliability was assessed using Cronbach’s a. In the baseline
study, Cronbach’s a was 0.96, with an internal consistency for each
subscale ranging from 0.72 to 0.94.8 In the 2-year follow-up study,
Cronbach’s a was 0.91, ranging from 0.91 to 0.94 in the subscales
and ranging from 0.87 to 0.94 and 0.91 and 0.94 for surgical and
nonsurgical groups, respectively. With respect to the exploratory
analysis, the RC-QOL subscales had excellent internal consistency at
both time intervals. These results are within normal limits when
used for clinical purposes as this questionnaire is intended. In this
2-year follow-up study, the WORC was used as a reference standard
and relatively stable Cronbach’s a between domains (0.91-0.94).
Floor and ceiling effects were used to evaluate content validity.
In the baseline study, no ﬂoor or ceiling effects were found as no
patients scored at the lowest end and no more than 2.9% at the
highest end.8 In the 2-year study, there was also an absence of ﬂoor
or ceiling effects in the RC-QOL overall and within each domain.
Thus, the RC-QOL was not only able to measure the entire spectrum
of a patient’s condition but also discriminate between patients
doing poorly and those doing well. A ceiling effect was found in 3
questions of the SOCIAL/EMOTIONAL domain of the WORC. This
may affect the WORC’s discrimination properties in rotator cuff
patients.
Criterion validity was assessed in the 2-year study by means of
concurrent validity using the Spearman rank correlation (rs) and
Lin’s concordance correlation coefﬁcient (rc). Strong positive
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Figure 3 Raw Rotator Cuff Quality of Life (RC-QOL) index change score between 2-year time intervals vs. the 7-point global rating scale (7-point GRS) in patients with rotator cuff
disease.

Figure 4 Raw Rotator Cuff Quality of Life (RC-QOL) index change score between 2-year time intervals vs. the visual analog global rating scale (VAS GRS) in patients with rotator cuff
disease.

change scores. Ultimately, this method exhibited small ES, or a
small difference between baseline and 2-year follow-up scores, in
the overall group as well as in nonsurgical patients (0.48 and 0.43).
The RC-QOL provides clinicians with an insight into the symptomatic, functional, and psychological aspects that pertain specifically to patients with rotator cuff disease. This becomes most
important when developing appropriate treatment and management strategies. The RC-QOL also provides a combined score in
addition to individual subscale scores, allowing it to serve as an
evaluative, discriminative, and predictive instrument.3,14

While the WORC has been shown in this study to correlate well
with the RC-QOL, they differ in several aspects. First, the RC-QOL
evaluates activities that are more physically demanding (ie,
mopping the ﬂoor, carrying 4.54-6.8 kg). These activities substantially affect symptoms in patients with rotator cuff disease.14 Second, the RC-QOL demonstrates its ability to discriminate patients in
the SOCIAL/EMOTIONAL domain when assessing patients overall
and when comparing surgical and nonsurgical groups. The WORC
has not demonstrated this in the sample group. Lastly, the RC-QOL
provides patients with the option of answering “Not applicable” on
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Figure 5 Raw Rotator Cuff Quality of Life (RC-QOL) index change score between 2-year intervals vs. the 7-point global rating scale (7-point GRS) in surgical patients with rotator cuff
disease.

Figure 6 Rotator Cuff Quality of Life (RC-QOL) index change score between 2-year intervals vs. the visual analog global rating scale (VAS GRS) in surgical patients with rotator cuff
disease.

items, which can increase the risk of satisﬁcing behavior.19 This
behavior, ﬁrst described by Herbert Simon, indicates that people
often satisﬁce, or settled for a good enough option, when making
decisions.33 Typically this occurs in respondents who lack the
cognitive capacity to comprehend what is being asked or lack the
motivation to answer it thoughtfully.33 However, in this case, patients are less likely to satisﬁce because they are motivated by the
perception that their answers will likely inﬂuence their medical
care.
Another important clinical ﬁnding is that rotator cuff patients
treated surgically may score higher than their nonsurgical

counterparts at approximately 2 years after baseline. Mean change
scores were consistently higher in all domains for surgical patients,
improving by a mean score of þ38 points compared to þ26 in
nonsurgical patients. This may suggest that the RC-QOL may be
more responsive in a surgical population.
Limitation
The appropriate use of anchor-based methods of determining
responsiveness ultimately depends on the quality of the external
anchors. A limitation arises in that we cannot distinguish between
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Figure 7 Raw Rotator Cuff Quality of Life (RC-QOL) index change score between 2-year intervals vs. the 7-point global rating scale (7-point GRS) in nonsurgical patients with rotator
cuff disease.

Figure 8 Rotator Cuff Quality of Life (RC-QOL) index change score between 2-year intervals vs. the visual analog global rating scale (VAS GRS) in surgical patients with rotator cuff
disease.

not statistically different in age and sex characteristics as those that
participated at baseline.

the possibility of a poor index and the possibility of poor external
anchors when evaluating these techniques. Additionally, an issue
for any cohort study is loss to follow-up usually due to 2 concerns;
the dropout rate is different between groups that are being evaluated, or the patients that decided to drop out are not the same as
the patients that decided to participate.7 A reasonable loss to
follow-up differs within the literature but is typically as little as 5%
with minor concerns for validity to >20% causing extreme concerns
in affecting the validity of the study.7 A loss of 25% to follow-up
occurred at the 2-year follow-up interval of this study. While this
appears to violate certain guidelines, it is important to note that
patient groups that participated at the 2-year time interval were

Conclusion
The RC-QOL is an easy-to-administer, economical tool that
accurately evaluates quality of life, discriminates between patients
based on function, and has predictive properties that can provide
insight into which patients will likely be successful with nonoperative treatment programs.3,14 Due to a lack of consensus on
appropriate measures of responsiveness, more testing using alternate distribution- and anchor-based analyses is important to
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further bolster the quality of the RC-QOL. Testing structural validity
via exploratory factor analysis should be considered as the next
step in evaluating the RC-QOL.

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Disclaimers:
Funding: No funding was disclosed by the authors.
Conﬂicts of interest: The authors, their immediate families, and any
research foundation with which they are afﬁliated have not
received any ﬁnancial payments or other beneﬁts from any commercial entity related to the subject of this article.
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