Reliability and Validity of the Osteoarthritis Research Society International Minimal Core Set of Recommended Performance-Based Tests of Physical Function in Knee Osteoarthritis in Community-Dwelling Adults

Construct Validity and Responsiveness of Performance-based Tests in Individuals With Knee Osteoarthritis

OBJECTIVES

To assess the construct validity and responsiveness of 3 performance-based tests in individuals with knee osteoarthritis (KOA).

DESIGN

This study has a prospective cohort design.

SETTING

Assessments were administered at the Federal University of São Carlos (Brazil) by 3 different raters.

PARTICIPANTS

A total of 107 participants with KOA were aged ≥40 years (N=107).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

This study assessed the construct validity and responsiveness of 3 performance-based tests: 40-meter fast-paced walk test (40-m FPWT), 11-step stair climb test (11-step SCT), and 30-second chair stand test (30-s CST). The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS), sedentary behavior (activPAL), and numeric pain rating scale (NPRS) were used as comparator instruments. Measurements were obtained at baseline and after 6 months. The construct validity and responsiveness were calculated using Spearman correlation coefficient within predefined hypotheses based on a panel comprising 5 experts in the field of outcome measurement in KOA.

RESULTS

The three performance-based tests showed excellent (ICC>0.9) reliability (intra and inter); however, only the 40-m FPWT and 11-step SCT were considered valid and responsive because both confirmed >75% of the priori hypotheses. The 30-s CST was not considered valid or responsive because it has not confirmed ≥75% of the priori hypotheses.

CONCLUSION

The 3 performance-based tests are reliable for intra and inter assessments. The 40-m FPWT and 11-step SCT are both valid and responsive for measuring physical function in patients with KOA. The 30-s CST was not considered valid or responsive. Therefore, 40-m FPWT and 11-step SCT can detect changes over time and are indicated for functional assessment in clinical practice.

People at a persistent pain service can walk it, but some struggle to talk about it: Reliability, detectable difference and clinically important difference of the six-minute walk test

OBJECTIVES

The six-minute walk test (6MWT) is a commonly used measure of functional capacity. This study is the first to investigate the test-retest reliability, minimal detectable difference (MDD) and the minimal clinically important difference (MCID) for people attending a persistent pain service. Relationships between change in 6MWT performance and change in self-reported physical, functional and psychological outcome measures were also explored.

METHODS

A cross-sectional repeated measures design was used with people having >9 months of pain attending an 8-week outpatient persistent pain programme. For reliability and MDD, 27 people were recruited, for MCID calculations, 32 people were recruited. The MCID was examined by dichotomising people into "improvers", or "non-improvers" based upon the Global Rating of Change (GRC) in physical abilities score.

RESULTS

The mean (SD) 6MWT distance was 389.4 (93.6) m at programme start, and 427.8 (83.0) m at week eight completion. The test-retest reliability was good (intraclass correlation coefficient = 0.89) and the MDD = 86.1 m. As there was no relationship between change in 6MWT distance and GRC physical abilities at week eight (r = 0.132, p = 0.472) the MCID could not be calculated. Furthermore, no relationships were found between change in 6MWT distance and other self-reported measures. Changes in GRC physical abilities and 6MWT were frequently discordant, with increased 6MWT for 7/11 "GRC non-improvers" and decreased 6MWT for 7/21 "GRC improvers".

CONCLUSIONS

Amongst this cohort, change in physical ability may or may not be reflected by self-reported change. Objective tests of physical ability are recommended for people attending pain services, and validated tests should align with intervention aims.

Validity of the Osteoarthritis Research Society International (OARSI) recommended performance-based tests of physical function in individuals with symptomatic Kellgren and Lawrence grade 0-2 knee osteoarthritis

BACKGROUND

Performance-based physical tests have been widely used as objective assessments for individuals with knee osteoarthritis (KOA), and the core set of tests recommended by the Osteoarthritis Research Society International (OARSI) aims to provide reliable, valid, feasible and standardized measures for clinical application. However, few studies have documented their validity in roentgenographically mild KOA. Our goal was to test the validity of five performance-based tests in symptomatic KOA patients with X-ray findings of Kellgren and Lawrence (K-L) grade 0-2.

METHODS

We recruited a convenience sample of thirty KOA patients from outpatient clinics and 30 age- and sex-matched asymptomatic controls from the community. They performed five OARSI-recommended physical tests and the KOA group answered the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index. The tests included the 9-step stair-climbing test (9 s-SCT), timed up and go (TUG) test, 30-second chair-stand test (30sCST), 40-m fast walking-test (40MFPW) and 6-minute walking test (6MWT). The discriminant validity of these physical tests were assessed by comparisons between the KOA and control groups, receiver operating curve and multivariate logistic regression analysis. The convergent/divergent validity was assessed by correlation between the physical tests results and the three subscale scores of the WOMAC in the KOA group.

RESULTS

The KOA group had significantly worse performance than the control group. The percentage of difference was the largest in the 9 s-SCT (57.2%) and TUG tests (38.4%). Meanwhile, Cohen's d was above 1.2 for the TUG test and 6MWT (1.2 ~ 2.0), and between 0.8 and 1.2 for the other tests. The areas under the curve to discriminate the two groups were mostly excellent to outstanding, except for the 30sCST. Convergent validity was documented with a moderate correlation between the 9 s-SCT and the physical function (WOMAC-PF) subscale scores (Spearman's ρ = 0.60).

CONCLUSIONS

The OARSI recommended core set was generally highly discriminative between people with K-L grade 0-2 KOA and their controls, but convergent/divergent validity was observed only in the 9 s-SCT. Further studies are required to evaluate the responsiveness of these tests and understand the discordance of physical performance and self-reported measures.