Reliability of the hand held dynamometer in measuring muscle strength in people with interstitial lung disease

Objective To evaluate the inter-rater and intra-rater reliability of the hand held dynamometer in measuring muscle strength in people with interstitial lung disease (ILD). Design Test retest reliability of hand-held dynamometry for elbow flexor and knee extensor strength between two independent raters and two testing sessions. Setting Physiotherapy department within a tertiary hospital. Participants Thirty participants with ILD of varying aetiology were included. Twenty participants completed the inter-rater reliability protocol (10 idiopathic pulmonary fibrosis, mean (SD) age 73 (10) years, 11 male) and 21 participants completed the intra-rater reliability protocol (10 idiopathic pulmonary fibrosis, mean age 71 (10) years, 11 male). Main outcome measures Mean muscle strength (kg). Agreement between the two raters and testing sessions was analyzed using Bland–Altman plots and reliability was estimated using intraclass correlation coefficients (ICC). Results For elbow flexor strength there was a mean difference between raters of −0.6 kg (limits of agreement (LOA) −5.6 to 4.4 kg) and within raters of −0.3 kg (LOA −2.8 to 2.3 kg). The ICCs were 0.95 and 0.98, respectively. For knee extensor strength there was a mean difference between raters of −1.5 kg (LOA −6.9 to 3.9 kg) and within raters of −0.7 kg (LOA −3.9 to 2.4 kg). The ICCs were 0.95 and 0.97, respectively. Conclusions Hand-held dynamometry is reliable in measuring elbow flexor and knee extensor strength in people with ILD.