An interactive voice response diary for patients with non-dystrophic myotonia

Abstract

Introduction: Non-dystrophic myotonia (NDM) is caused by mutations in muscle chloride and sodium channels. Currently, there is no standardized instrument for documenting symptom frequency and severity in NDM.

Methods: Subjects used an automated, interactive, telephone-based voice response diary (IVR) to record frequency and severity of stiffness, weakness, pain, and tiredness once a week for 8 weeks, after their baseline visits.

Results: We describe the IVR and report data on 76 subjects for a total of 385 person-weeks. Overall there were 5.1 calls per subject. Forty-eight subjects called in 5 or more times, and 14 called in 8 times. Stiffness was both the most frequent and severe symptom. Warm-up and handgrip myotonia were associated with higher severity scores for stiffness.

Conclusions: IVR is a convenient technology to allow patient reporting of repeated and real-time symptom frequency and severity, and it is presently being used in a trial of mexiletine in NDM.

Figure 1

Flow diagram illustrating the subject call-in process for the IVR. All subjects are identified by entering a participant ID. Then they are asked to enter 1 for yes or 2 for no whether they had a given symptom (stiffness, pain, weakness, tiredness) in the preceding week. Second tier questions ask them to estimate the number of days in a given week the symptom is experienced and then to estimate the symptom severity on a 1-9 ranked scale.

Figure 2

IVR—frequency and severity of reported symptoms. A. Weekly frequency of reported symptoms (n=76, total of 385 person-weeks recorded). Subjects were considered to have the given symptom if they answered yes to the first tier question whether they experienced a given symptom in the prior week. Stiffness was the most frequently reported symptom at 344 weeks (89.4% of total person-weeks reported). B. Mean symptom severity (n=76, total of 385 person-weeks recorded). If subjects experienced a given symptom in the prior week they were asked to rate severity on a 1-9 ranked scale, 1 being minimal and 9 being the worst ever experienced. If a symptom was not experienced, severity was assumed to be 0. Stiffness was the most severe symptom recorded with a mean of 3.85. C. Standard deviation for symptom reported (n=76, total 385 person-weeks recorded). The within subject standard deviation was less than between subject standard deviation for all symptoms reported. The standard deviation was relatively high compared to the mean for each symptom category and may reflect natural variation in week-to-week symptomology in subjects with NDM. D. Mean severity score by genetic mutation. There were significantly higher severity scores for tiredness (p=0.04) and pain (p=0.007) for DM2 compared to chloride channel mutations. * = p< 0.05, ** p< 0.01, *** = p< 0.001.