Muscular Dystrophy Surveillance Tracking and Research Network (MD STARnet): case definition in surveillance for childhood-onset Duchenne/Becker muscular dystrophy

Abstract

The Muscular Dystrophy Surveillance Tracking and Research Network (MD STARnet) is a multisite collaboration to determine the prevalence of childhood-onset Duchenne/Becker muscular dystrophy and to characterize health care and health outcomes in this population. MD STARnet uses medical record abstraction to identify patients with Duchenne/Becker muscular dystrophy born January 1, 1982 or later who resided in 1 of the participating sites. Critical diagnostic elements of each abstracted record are reviewed independently by >4 clinicians and assigned to 1 of 6 case definition categories (definite, probable, possible, asymptomatic, female, not Duchenne/Becker muscular dystrophy) by consensus. As of November 2009, 815 potential cases were reviewed. Of the cases included in analysis, 674 (82%) were either ''definite'' or ''probable'' Duchenne/Becker muscular dystrophy. These data reflect a change in diagnostic testing, as case assignment based on genetic testing increased from 67% in the oldest cohort (born 1982-1987) to 94% in the cohort born 2004 to 2009.

Figure 1

Summary of MD STARnet approach to case abstraction, review, and pooling.

Figure 2

Data used for case assignment by birth year intervals. The diagnostic test (on either proband or a maternal family member) used to assign diagnostic classification for ‘definite’ and “probable” cases was identified through review of Clinical Review Committee reports. The graph shows change in the percent of cases assigned by dystrophin mutation, muscle biopsy, or X-linked family history in 5-year intervals. There is a steady increase in percentage of cases with dystrophin mutations, particularly for those born after 1997 (predicted diagnosis in 2002).