Intra-Rater Reliability and Concurrent Validity of Quantified Muscle Testing for Maximal Knee Extensors Strength in Men with Myotonic Dystrophy Type 1

Abstract

BACKGROUND: Myotonic dystrophy type 1 (DM1) is the most prevalent degenerative neuromuscular disease in adults. Knee extensor (KE) maximal strength loss is a strong indicator of physical limitations in DM1. A reliable, precise and accessible maximal strength evaluation method needs to be validated for this slowly progressive disease. OBJECTIVE: This paper aims to assess the intra-rater reliability, the standard error of measurement (SEM), the minimal detectable change (MDC), and the concurrent validity of quantified muscle testing (QMT) using a handheld dynamometer with a gold standard: the Biodex isokinetic device. METHODS: Nineteen men with the adult form of DM1 participated in this study by attending 2 visits spaced by one week. The evaluation of KE muscle strength with QMT was completed on the first visit and the same QMT evaluation in addition to the maximal muscle strength evaluation using an isokinetic device were performed on the second visit. RESULTS: The intra-rater reliability was excellent with an intraclass correlation coefficient (ICC) of 0.98 (0.96-0.99: 95% confidence interval). SEM and MDC values were 1.05 Nm and 2.92 Nm, respectively. Concurrent validity of QMT of KE muscle group with the Biodex was also excellent with a Spearman's correlation of ρ = 0.98. CONCLUSIONS: The excellent concurrent validity and intra-rater reliability, and the small SEM and MDC of the QMT make this test a method of choice, in either a clinical or research setting, to precisely evaluate muscle strength impairments of the KE in men with DM1.

Portable fixed dynamometry: towards remote muscle strength measurements in patients with motor neuron disease

“…Optimizing muscle strength testing is important to optimize the evaluation of efficacy of new MND therapies and to contribute to the delivery of remote care [20]. In the field of voluntary muscle strength testing, the Biodex system is considered to be the gold standard [21,37,38] [16,39] These rigid frameworks are, however, not portable, require visits to the out-patient department, and are still operated by a trained examiner. Other methods that are applied to fixate dynamometers are belt or clamp fixations and stabilization devices [18,37,[40][41][42][43][44].…”

Explanatory factors of dynamic balance impairment in myotonic dystrophy type 1

“…The handheld dynamometer used was the MEDup™ linear electronic handheld dynamometer (Atlas medic, Québec, Canada). QMT has shown evidence of reliability and validity for knee extension in the DM1 population 25 . For each muscle group, at least two trials were done: if results differed by more than 10%, a third or fourth trial was done.…”

“…QMT has shown evidence of reliability and validity for knee extension in the DM1 population. 25 For each muscle group, at least two trials were done: if results differed by more than 10%, a third or fourth trial was done. The mean of the two closest trials for each side was kept.…”

Outcome measures frequently used to assess muscle strength in patients with myotonic dystrophy type 1: a systematic review

“…From the 39 studies that used quantitative muscle test, 17 studies did not report the method used [57,[68][69][70]73,[75][76][77][78][79]81,82,85,86,107,108,110], ten studies assessed maximum isometric torque [53,59,62,63,65,[70][71][72]79,108], seven studies assessed maximal voluntary isometric contraction [54,55,58,66,67,73,87] Maximal voluntary isometric contraction was used to assess the strength of Abductor digiti minimi [54], ankle dorsiflexors [58,87], ankle plantar flexors [87], grip strength [56,66,67], elbow flexors [73], elbow extensors [73], hip abductors [87], hip extensors [87], knee extensors [58, 73,87], knee flexors [73,87] and pinch strength [56]. Maximal voluntary isometric contraction results were between...…”

“…Only 17 studies reported on longitudinal data: a cardiac study [105], 14 skeletal muscle strength studies [55,59,61,62,68,70,71,72,76,79,80,81,86,105], and two respiratory muscle strength studies [88,93].…”