Interobserver Reliability of Peripheral Muscle Strength Tests and Short Physical Performance Battery in Patients With Chronic Obstructive Pulmonary Disease: A Prospective Observational Study

Abstract

Objective: To evaluate the interobserver reliability of the Short Physical Performance Battery (SPPB) and hand dynamometry when measuring isometric muscle strength in people with chronic obstructive pulmonary disease (COPD).

Design: Reliability study. Each patient was assessed by a pulmonology physician and a physical therapist in 2 separate sessions 7 to 14 days apart (mean, 9.8±0.8d). Each rater was blinded to the other's results.

Setting: Pneumology unit of a public hospital.

Participants: Random sample of outpatients with stable COPD (N=30).

Interventions: Not applicable.

Main outcome measures: SPPB and muscle strength (kg) using electronic handgrip and handheld dynamometers. Reliability was assessed with intraclass correlation coefficients (ICCs), standard error of measurement values, and Bland-Altman plots. ICCs were calculated for the SPPB summary score and for its 3 subscales.

Results: The ICCs for the overall reliability of the SPPB summary score and for grip and quadriceps strength were .82 (95% confidence interval [CI], .62-.91), .97 (95% CI, .93-.98), and .76 (95% CI, .49-.88), respectively. The standard error of measurement values were .55 points, 1.30kg, and 1.22kg, respectively. The mean differences between the rater's scores were near zero for grip strength and SPPB summary score measures. The ICCs for the SPPB subscales were .84 (95% CI, .66-.92) for the chair subscale, .75 (95% CI, .48-.88) for gait, and .33 (95% CI, -.42 to .68) for balance.

Conclusions: Interobserver reliability was good for quadriceps and handgrip dynamometry and for the SPPB summary score and its chair stand and gait speed subscales. Both pulmonary physicians and physical therapists can obtain and exchange the scores. Because the reliability of the balance subscale was questionable, it is better to use the SPPB summary score.

Keywords: Muscle strength; Pulmonary disease, chronic obstructive; Rehabilitation.