Abstract
Introduction We evaluated construct validity (structural validity and hypothesis-testing) and reliability (test-retest reliability, measurement error and internal consistency) of the new TENDINopathy Severity assessment-Achilles (TENDINS-A), which is the only outcome measure with adequate content validity for assessment of disability in Achilles tendinopathy.
Materials and Methods Participants with Achilles tendinopathy completed an online survey: demographics, TENDINS-A, Foot and Ankle Outcome Score (FAOS) and Victorian Institute of Sport Assessment-Achilles (VISA-A). Exploratory factor analysis (EFA) evaluated dimensionality. Confirmatory Factor Analysis (CFA) evaluated structural validity [Comparative Fit Index (CFI); Standardised Root Measure Square (SRMS)]. Correlations between TENDINS-A and the FAOS/VISA-A evaluated hypothesis-testing. Intraclass correlation co-efficient (ICC) represents test-retest reliability. Cronbach’s α represents internal consistency. Standard error of the measurement (SEM) represents measurement error.
Results Seventy-nine participants (51% female) with a mean (SD) age= 42.6 (13.0) years, height= 175.0 (11.7) cm and body mass= 82.0 (19.1) kg were included. EFA identified three meaningful factors, proposed to be pain, symptoms and function. The best model identified using CFA had adequate structural validity (CFI= 0.959, SRMS=0.068), excluded three items from the original TENDINS-A and included three factors (Pain, Symptoms, and Function). The TENDINS-A exhibited moderate positive correlation with FAOS (rho=0.598,p<0.001), and moderate, negative correlation with VISA-A (r=-0.639,p<0.001). Reliability of the TENDINS-A is excellent (ICC=0.930; Cronbach’s α=0.808; SEM=6.54 units).
Conclusions Our evaluation of the revised 10-item TENDINS-A has determined it has adequate validity and reliability. Thus, the TENDINS-A can be recommended for immediate use, being the preferred tool over all others to assess disability in Achilles tendinopathy.
