Preliminary psychometric evaluation of a measure of adherence to
Document Sample
Original Research
Preliminary psychometric
evaluation of a measure of
adherence to clinic-based sport
injury rehabilitation
Britton W. Brewer, Judy L. Van Raalte, Albert J. Petitpas, Joseph H. Sklar,
Mark H. Pohlman, Robert J. Krushell, Terry D. Ditmar, Joanne M. Daly
Britton W. Brewer and Jeremiah Weinstock
PhD, Judy L. Van
Raalte PhD, Albert J.
Petitpas EdD,
Joanne M. Daly MS, Objectives: to examine the psychometric properties of the Sport Injury Rehabilitation Adherence
Department of Scale (SIRAS), an instrument designed to assess adherence during clinic-based sport injury
Psychology,
Spring®eld College, rehabilitation sessions. Design: rehabilitation professionals completed the SIRAS for their patients
Spring®eld, on one occasion in Study 1, two occasions one week apart in Study 2, and multiple (range 6±48)
MA 01109, USA
occasions in Study 3. Setting: an orthopedic physical therapy clinic specializing in sports medicine.
Joseph H. Sklar MD,
Participants: one hundred and forty-®ve general physical therapy patients in Study 1, 31 patients
Mark H. Pohlman
MD, Robert J. undergoing rehabilitation following knee surgery in Study 2, and 43 patients undergoing
Krushell MD, New rehabilitation following anterior cruciate ligament reconstruction in Study 3. Main outcome
England Orthopedic
Surgeons, measure: the SIRAS. Results: In Study 1, a Cronbach's alpha coef®cient of .82 was obtained for the
Spring®eld, SIRAS, scores on the SIRAS were weakly correlated (r .21) with attendance at rehabilitation
MA 01109, USA
sessions, and the SIRAS items loaded on a single factor in a principal components analysis. In
Terry D. Ditmar
Study 2, a test±retest intraclass correlation coef®cient of .77 was obtained for the SIRAS and, in
BS PT, Baystate
Outpatient Study 3, a modi®ed interrater intraclass correlation coef®cient of .57 was obtained for repeated
Rehabilitation, administrations of the SIRAS across rehabilitation professionals. Conclusions: the results of this
3300 Main Street,
Spring®eld, MA, study provide preliminary evidence in support of the internal consistency, unidimensionality,
USA discriminant validity, test±retest reliability, and interrater reliability of the SIRAS. # 2000 Harcourt
Jeremiah Weinstock Publishers Ltd
BA, Department of
Psychology,
University of
Memphis, Memphis,
TN, USA
Introduction positive associations between treatment
Correspondence to: adherence and rehabilitation outcomes have
Britton W. Brewer,
Patient adherence to prescribed rehabilitation been obtained in studies of clinic attendance for
Center for
Performance protocols is considered vital to achieving various injuries (Derscheid & Feiring 1987),
Enhancement and successful outcomes in physical therapy exercise session attendance for knee
Applied Research,
(Clopton & McMahon 1992; Ice 1995; Merrill osteoarthritis (Ettinger et al. 1997; Rejeski et al.
Department of
Psychology, 1994). Case history data have documented the 1997), activity restriction for humerus fractures
Spring®eld College, adverse effects of poor treatment adherence on (Hawkins & Switlyk 1993), and splint wearing
Spring®eld,
Massachusetts
rehabilitation outcomes for rehabilitation for hand dysfunction (Rives et al. 1992).
01109, USA. regimens involving some combination of rest, A number of predictors of adherence to sport
Tel: 1 413 748 3696; immobilization, and cryotherapy for shoulder injury rehabilitation programs have been
Fax: 14137483854;
E-mail: bbrewer@ injuries (Hawkins 1989) and leg injuries (Meani identi®ed. These predictors include self-
sp¯dcol.edu et al. 1986; Satter®eld et al. 1990). In addition, motivation (Duda et al. 1989; Fields et al. 1995;
68 Physical Therapy in Sport (2000) 1, 68±74 * 2000 Harcourt Publishers Ltd
c
Psychometric properties of the SIRAS
Fisher et al. 1988; Noyes et al. 1983), belief in treatment regimen when rehabilitation is not
the ef®cacy of treatment (Duda et al. 1989; proceeding as expected.
Noyes et al. 1983; Taylor & May 1996), comfort The purpose of this investigation was to
of the clinical environment (Fields et al. 1995; examine the psychometric properties of a brief
Fisher et al. 1988), convenience of rehabilitation measure of adherence during clinic-based sport
scheduling (Fields et al. 1995; Fisher et al. 1988), injury rehabilitation that is suf®ciently general
social support for rehabilitation (Byerly et al. to be applicable across diagnoses, rehabilitation
1994; Duda et al. 1989; Fisher et al. 1988), and protocols, and patient populations. The
mood disturbance (Daly et al. 1995). measure's internal consistency, discriminant
As noted in a recent review of the literature validity, and relationship to demographic
(Brewer 1998), attendance at rehabilitation factors were assessed in Study 1. Study 2
sessions (i.e. number of rehabilitation sessions examined the measure's test±retest reliability,
attended divided by number of rehabilitation and Study 3 evaluated the measure's interrater
sessions scheduled) is the measure of adherence reliability and internal consistency over
that has been used most frequently in sport repeated administrations.
injury rehabilitation research investigations.
Although the attendance index is easily
obtained and calculated, it provides no Study 1
information about what patients actually do Method
during rehabilitations sessions and typically
produces negatively skewed distributions give Participants: participants in this study were 145
consecutive patients (82 males, 62 females, one
the general tendency for patients to attend most
did not report gender) at an orthopedic
scheduled rehabilitation sessions (Brewer 1998).
physical therapy clinic specializing in sports
Clinic-based sport injury rehabilitation
medicine who had attended at least three
programs require patients not only to show up
rehabilitation appointments (M 12.41,
for scheduled appointments, but also to
S.D. 12.81). The mean age of participants was
participate actively in exercises and other
43.95 (S.D. 15.54) years. In terms of sport
therapeutic activities (e.g. cryotherapy,
involvement, 20 participants identi®ed
phonophoresis). A patient could have perfect
themselves as competitive athletes, 64
attendance at rehabilitation sessions, yet given
participants identi®ed themselves as
only minimal effort or cooperate less than fully recreational athletes, and 60 participants
with rehabilitation practitioners during the identi®ed themselves as nonathletes (one
sessions. Consequently, there is a need for a participant did not respond to the sport
concise, psychometrically sound measure of involvement item). Nonathletes were included
adherence during clinic-based sport injury in the sample for purposes of comparison with
rehabilitation activities that re¯ects patients' athletes and to examine the applicability of the
actual rehabilitation behavior. SIRAS to nonathletic populations. The injuries
By virtue of their close and frequent contact for which participants were receiving treatment
with patients in the sport injury rehabilitation varied extensively and included most of the
setting (Brewer et al. 1999), rehabilitation diagnoses identi®ed by Derscheid and Feiring
practitioners are in an excellent position to (1987) as common at a sports medicine clinic
evaluate what patients actually do during (e.g. torn anterior cruciate ligament,
rehabilitation sessions. Consequently, patellofemoral syndrome, torn meniscus,
rehabilitation practitioners constitute an shoulder impingement, chondromalacia
important potential resource in the assessment patella).
of adherence to clinic-based sport injury Measures: a brief demographic questionnaire
rehabilitation programs. Further, knowledge of was used to assess participants' age, gender,
patients' adherence to clinic-based activities can and level of sport involvement (i.e. nonathlete,
help rehabilitation practitioners determine recreational athlete, competitive athlete). Patient
whether to modify the treatment protocol or to attendance at rehabilitation sessions was
attempt to enhance adherence to the current monitored and, for each participant, a ratio of
* 2000 Harcourt Publishers Ltd
c Physical Therapy In Sport (2000) 1, 68±74 69
Physical Therapy in Sport
sessions attended to sessions scheduled was therapists and athletic trainers. Because the
calculated. Attendance has been used as an distribution for the attendance ratio was
adherence measure in previous research on negatively skewed, an arcsin transformation for
sport injuries (Byerly et al. 1994; Daly et al. proportional data (Winer et al. 1991) was
1995; Derscheid & Feiring 1987; Duda et al. performed on attendance scores.
1989; Fields et al. 1995; Fisher et al. 1988; Data analysis: a Cronbach's alpha coef®cient
Lampton et al. 1993; Laubach et al. 1996; Udry was calculated for SIRAS item scores to
1997) and other medical conditions (Brookes examine internal consistency. To evaluate the
1992; Ettinger et al. 1997; Rejeski et al. 1997). factor structure of the SIRAS items and explore
Items for the Sport Injury Rehabilitation the acceptability of summing the individual
Adherence Scale (SIRAS) were derived from the items, a principal components analysis with
adherence literature (Duda et al. 1989; varimax rotation was performed. Discriminant
Meichenbaum & Turk 1987). The SIRAS is a validity was assessed by performing a Pearson
three-item measure in which rehabilitation correlation between the sum of the SIRAS item
practitioners rate participants' intensity of scores and the attendance ratio. To identify
completion of rehabilitation exercises, potential differences in SIRAS scores as a
frequency of following practitioner instructions function of gender and level of sport
and advice, and receptivity to changes in the involvement, a 2 (Gender) by 3 (Level of Sport
rehabilitation program during that day's Involvement) analysis of variance (ANOVA)
appointment on 5-point Likert-type scales (see was performed on total SIRAS scores. A
Table 1 for the complete scale with anchors). Pearson correlation coef®cient was calculated
Procedure: in accord with institutional review between age and the sum of the SIRAS scores to
board policy, patients completed an informed determine whether scores on the SIRAS vary
consent form prior to participation in the study. systematically with age. Finally, a oneway
The physical therapists (n 8), athletic trainers ANOVA was performed on total SIRAS scores
(n 5), physical therapy assistants (n 2), and to examine differences in adherence ratings
occupational therapist (n 1) at the clinic across the various types of rehabilitation
completed the SIRAS for each of their patients practitioners (i.e. physical therapist, athletic
participating in the study. Among the patients trainer, physical therapy assistant, occupational
who were invited to participate in the study, 22 therapist) involved in the study.
declined, ®ve noted that they did not speak
English, and two stated that they could not read
or write. Participant attendance at rehabilitation Results and Discussion
sessions over the course of their treatment to Descriptive statistics for scores on the SIRAS are
date was also recorded by the physical presented in Table 2. The internal consistency
of the SIRAS was found to be acceptable
Table 1 Sport Injury Rehabilitation Adherence Scale
(Cronbach's alpha 0.82). Principal
1. Circle the number that best indicates the intensity components analysis with varimax rotation
with which this patient completed rehabilitation revealed a single factor accounting for 74% of
exercises during today's appointment:
minimum effort 1 2 3 4 5 maximum effort Table 2 Means and Standard Deviations of Sport
Injury Rehabilitation Adherence Scale Scores in Studies
2. During today's appointment, how frequently did this 1, 2, and 3
patient follow your instructions and advice?
never 1 2 3 4 5 always N M S.D.
Study 1 145 12.55 2.30
3. How receptive was this patient to changes in the
rehabilitation program during today's appointment? Study 2
very unreceptive 1 2 3 4 5 very receptive Time 1 31 11.68 2.43
Time 2 31 11.81 2.44
Note: The Sport Injury Rehabilitation Adherence Scale Study 3
can also be used with reference to adherence tendencies Primary provider 43 14.22 0.82
in general by using the present tense (without reference Secondary provider 39 13.59 1.58
to `today's appointment').
70 Physical Therapy in Sport (2000) 1, 68±74 * 2000 Harcourt Publishers Ltd
c
Psychometric properties of the SIRAS
the variance in SIRAS scores patellar realignment). To meet selection criteria,
(eigenvalue 2.21). Results of the principal participants had to have been in physical
components analysis, along with the acceptable therapy for at least one week, had to have at
Cronbach's alpha value, suggest that the three least one week of rehabilitation appointments
items on the SIRAS can be summed to create a remaining, and had to identify themselves as
single score representing adherence to clinic- either a recreational athlete or a competitive
based sport injury rehabilitation. Rotated factor athlete. Participants had attended an average of
loadings for the effort, following instructions, 11.27 (S.D. 9.16) sessions prior to and
and receptivity to change items were 0.84, 0.84, including the sessions in which the SIRAS was
and 0.89, respectively. administered for the ®rst time.
Supporting the discriminant validity of the Procedure: in accord with institutional review
SIRAS, scores on the instrument were board policy, patients completed an informed
signi®cantly correlated with attendance at consent form prior to participation in the study.
rehabilitation sessions (r 0.21, P 5 0.05). The The invitation to participate in the study was
signi®cant positive correlation indicates that accepted by all patients approached. The
there is enough overlap between SIRAS scores physical therapists and athletic trainers
and attendance at rehabilitation sessions to supervising the care of patients participating in
suggest that they tap related aspects of the study completed the SIRAS immediately
rehabilitation, but the low positive magnitude after two clinic-based rehabilitation sessions
of the correlation suggests that the SIRAS approximately one week apart. The same
appears to provide unique information (over practitioner completed the SIRAS on both
and above attendance) about how well patients occasions.
adhere to the rehabilitation program. Data analysis: an intraclass correlation
The 2 (Gender) Â3 (Level of Sport coef®cient (ICC) was calculated using the (2, 1)
Involvement) ANOVA performed on total formula speci®ed by Shrout and Fleiss (1979) to
SIRAS scores revealed no signi®cant effects, examine the test±retest reliability of the sum of
indicating that SIRAS scores did not vary as a the SIRAS items for the two administrations of
function of participant gender and level of sport the scale one week apart.
involvement (i.e. nonathlete, recreational
athlete, competitive athlete). Participant age
was not signi®cantly correlated with Sport Results and Discussion
Injury Rehabilitation Adherence scores Descriptive statistics for scores on the SIRAS are
(r 0.09, P 4 0.05). The oneway ANOVA displayed in Table 2. A test±retest reliability
revealed no signi®cant differences in SIRAS coef®cient (ICC [2, 1]) of 0.77 was found for the
scores across the four types of rehabilitation SIRAS over a one-week period. The obtained
practitioner involved in the study. The ®ndings value, which gives evidence of the temporal
of Study 1 provide evidence in support of the stability of the SIRAS, is reasonably high given
internal consistency and discriminant validity that adherence to rehabilitation inevitably
of the SIRAS and suggest that it may be useful changes over time (Quinn 1996).
as a brief, unidimensional measure of
adherence during clinic-based sport injury
rehabilitation sessions. Study 3
Method
Study 2 Participants: participants in this study were 43
patients (33 males, 10 females) undergoing
Method
rehabilitation, following anterior cruciate
Participants: participants were 31 individuals ligament (ACL) reconstruction, at an orthopedic
(19 males and 12 females) who, as a result of physical therapy clinic specializing in sports
sport participation, acquired a knee injury medicine.
requiring either arthroscopic or open surgery Procedure: in accord with institutional review
(e.g. ACL reconstruction, meniscectomy, board policy, patients completed an informed
* 2000 Harcourt Publishers Ltd
c Physical Therapy In Sport (2000) 1, 68±74 71
Physical Therapy in Sport
consent form prior to participation in the study. providers and secondary providers are shown
The physical therapists (n 8), athletic trainers in Table 2. The intraclass correlation between
(n 7), and physical therapy assistants (n 2) primary and secondary provider mean ratings
supervising the care of the patients on the SIRAS was 0.57, suggesting that different
participating in the study completed the SIRAS sport rehabilitation professionals use the scale
immediately following each of the patients' in similar ways to observe the clinic-based
rehabilitation appointments. For any given rehabilitation behavior of patients. Although
patient's rehabilitation appointment, only one the correlation was in the moderate range, there
sport rehabilitation professional completed the are two main factors that could have attenuated
SIRAS. Across multiple rehabilitation the relationship. First, across patients, primary
appointments, however, SIRAS ratings were and secondary providers were often different
obtained by at least two sport rehabilitation individuals. For example, a primary provider
professionals for each patient, thus enabling an for one patient could have been a secondary
evaluation of the interrater reliability of the provider for another patient. Second, mean
SIRAS. SIRAS scores across appointments were used.
Data analysis: because some patients were This means that SIRAS scores assessed a
seen by more than two sport rehabilitation general tendency to adhere and did not
practitioners over the course of their treatment, correspond to patients' behavior for any
primary and secondary providers were particular appointment. Although the ®ndings
identi®ed on the basis of the frequency with of Study 2 indicate reasonable stability of
which they supervised each patient. The SIRAS scores across appointments, any patient
physical therapist or athletic trainer who had inconsistencies in adherence behavior across
supervised the largest number of a given rehabilitation sessions would have reduced the
patient's appointments was designated the magnitude of the association between primary
primary provider. The professional who had and secondary provider scores on the SIRAS.
supervised the second largest number of a For participants who had attended all of their
given patient's appointments was considered ®rst 10 sessions (n 32), a Cronbach's alpha
the secondary provider. For both primary and coef®cient of 0.86 for the multiple
secondary providers, mean numbers of administrations of the SIRAS was obtained.
appointments supervised and mean SIRAS This ®nding suggests that repeated assessments
scores across appointments were calculated. To of adherence during sport injury rehabilitation
evaluate interrater reliability of the SIRAS, an sessions using the SIRAS can be aggregated to
intraclass correlation coef®cient was calculated produce an internally consistent index of
between primary and secondary provider mean adherence to a clinic-based sport injury
ratings using the generic formula rehabilitation protocol.
recommended by Thomas and Nelson (1990).
The viability of aggregating scores on the
General discussion
SIRAS across repeated administrations was
explored by computing a Cronbach's alpha Studies 1±3 provide preliminary evidence for
coef®cient for patients who had attended all of the psychometric integrity of the SIRAS. In
their ®rst 10 sessions using their summed scale particular, the SIRAS is an internally consistent,
scores for each of the 10 sessions as individual unidimensional measure of adherence for clinic-
`items'. based sport injury rehabilitation (Study 1) that
is reasonably stable over time (Study 2) and
positively associated with attendance at
Results and Discussion
rehabilitation sessions (Study 1). Moreover,
Patients were supervised by their primary although a more accurate estimate of interrater
provider for a mean of 17.13 (S.D. 6.98, reliability should be obtained through
range 5±32) appointments and by their conventional means, it appears that based on
secondary provider for a mean of 3.85 the results of Study 3, the SIRAS can be reliably
(S.D. 3.09, range 1±12) appointments. used by different rehabilitation practitioners to
Mean scores on the SIRAS for primary assess an individual's adherence to clinic-based
72 Physical Therapy in Sport (2000) 1, 68±74 * 2000 Harcourt Publishers Ltd
c
Psychometric properties of the SIRAS
rehabilitation and that multiple administrations injury rehabilitation. Should research continue
of the SIRAS can be combined to form a reliable to demonstrate favorable psychometric
index of adherence to a clinic-based properties for the SIRAS, the measure could be
rehabilitation protocol. With regard to interrater applied in clinical settings. Clinical practitioners
reliability, given the unconventional nature of could use the SIRAS to identify patients
the research design in Study 3, there is a clear adhering poorly to rehabilitation activities or
need for studies in which multiple practitioners patients experiencing lapses in motivation to
observe the same sessions of patients. Such an engage in clinic-based rehabilitation activities.
approach would not only enable a more Interventions designed to enhance adherence to
accurate estimate of interrater reliability to be sport injury rehabilitation (Fisher et al. 1993;
obtained, but would also facilitate an Worrell 1992) could be directed toward patients
examination of the extent to which the identi®ed as adhering poorly with the SIRAS.
psychometric properties of the SIRAS are
in¯uenced by the nature of the training and the
Acknowledgements
amount of clinical experience of the
practitioners using the scale. This research was supported in part by grant
The generally positive results obtained in this number R15 AR42087-01 from the National
investigation for the SIRAS notwithstanding, it Institute of Arthritis and Musculoskeletal and
is important to note that practitioner ratings of Skin Diseases. Its contents are solely the
patient adherence involve subjective judgments responsibility of the authors and do not
and are, therefore, susceptible to bias. represent the of®cial views of the National
Consequently, to obtain a more complete Institute of Arthritis and Musculoskeletal and
assessment of adherence to clinic-based sport Skin Diseases.
injury rehabilitation, the SIRAS should be used Portions of these data were presented at (a)
in conjunction with measures of attendance at the 1994 annual meeting of the North American
rehabilitation sessions and other parameters Society for the Psychology of Sport and
speci®c to particular rehabilitation protocol Physical Activity, Clearwater Beach, Florida,
under consideration (e.g. percentage of USA; (b) the 1995 annual meeting of the
prescribed repetitions completed, heart rate Association for the Advancement of Applied
during rehabilitation exercises requiring Sport Psychology, New Orleans, Louisiana,
exertion). USA; and (c) the 1996 annual meeting of the
Further research should continue to evaluate Association for the Advancement of Applied
the psychometric properties of the SIRAS. One Sport Psychology, Williamsburg, Virginia,
potential avenue of inquiry with the SIRAS USA. The authors thank Mark Andersen, Cary
would be to examine predictors of adherence Gray, and Anastasia Syde-Carr for their helpful
during rehabilitation sessions. Correlations comments on an earlier draft.
between scores on the SIRAS and factors linked
to adherence to sport injury rehabilitation
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