Isometric maximal voluntary contraction testing via the quantitative muscle assessment device. (Participant positioning shown for the: (a) hip extensors and (b) elbow flexors.)
The Adult Myopathy Assessment Tool
Construct validity of the AMAT
Harris-Love MO, Fernández-Rhodes LE, Joe G, Shrader JA, Freeman BK, Auh S, Kokkinis AD, La Pean A, Chen C, Lehky TJ, Levy EW, Davenport T, Di Prospero NA, Fischbeck KH, 2014 (doi:10.1155/2014/873872)
The adult myopathy assessment tool (AMAT) is a performance-based battery comprised of functional and endurance subscales that can be completed in approximately 30 minutes without the use of specialized equipment.
Lower AMAT scores were associated with longer disease duration (r = −0.29; P < 0.03) and lower serum androgen levels (r = 0.49–0.59; p < 0.001) in a neuromuscular disease cohort. The AMAT was significantly correlated with strength and functional status (r = 0.82–0.88; p < 0.001). Additionally the domains of the AMAT exhibited good internal consistency (Cronbach's α = 0.77–0.89; p < 0.001).
The AMAT subscales are organized to be congruent with the disability models proposed by both the Institute of Medicine (IOM) and the World Health Organization (WHO).
Reliability of the AMAT
Harris-Love MO, Joe G, Davenport T, Koziol D, Abbett Rose K, Shrader JA, Vasconcelos OM, McElroy B, Dalakas M, 2014. (doi:10.1002/acr.22473)
Intrarater and interrater reliability correlation coefficients were ≥ 0.94 for the AMAT functional subscale, endurance subscale, and total score (all p < 0.02) in a myositis cohort. All AMAT items had satisfactory intrarater agreement (kappa statistics with Fleiss-Cohen weights, with values κw = 0.57-1.00). Interrater agreement was acceptable for each AMAT item (κ = 0.56-0.89, with the exception of the sit up task). The standard error of measurement and 95% confidence interval range for the AMAT total scores did not exceed 2 points across all observations (AMAT total score range 0-45).
Results of this study suggest that physicians and physical therapists may reliably score the AMAT following a single training session. The AMAT functional subscale, endurance subscale, and total score exhibit interrater and intrarater reliability suitable for clinical and research use.
The initial findings suggest that the AMAT is a reliable, domain-specific assessment of functional status and muscle endurance. Additional study is underway to examine the utility of the tool with other patient populations.