Background/Purpose: The epidemiology of mixed connective tissue disease (MCTD) is not well described. Leveraging data from the Manhattan Lupus Surveillance Program (MLSP), a racially/ethnically diverse population-based retrospective registry of cases with SLE and related diseases including MCTD, we provide estimates of the prevalence and incidence of MCTD in Manhattan.

Methods: The MLSP MCTD cases were identified from rheumatologists, hospitals and population databases using a variety of ICD-9 codes. Several case definitions to define MCTD were used: 1) Fulfillment of our modified Alarcon-Segovia and Khan criteria which required a positive RNP antibody and the presence of synovitis, myositis, and Raynaud’s phenomenon (all of which were systematically collected as part of the MLSP), 2) a diagnosis of MCTD and no other diagnosis of another connective tissue disease (CTD), and 3) a diagnosis of MCTD regardless of another CTD found in the charts. Prevalent cases were new or existing cases of MCTD aged 18 and older fulfilling the definitions outlined above and residing in Manhattan January 1–December 31, 2007. Incident cases were those fulfilling the same criteria residing in Manhattan, and first diagnosed with MCTD during January 1, 2007–December 31, 2009. Denominators were calculated from Department of Health and Mental Hygiene’s intercensal population estimates for Manhattan. Rates overall were calculated per 100,000 person-years and age-adjusted to the standard projected 2000 US population.

Results: Using our modified Alarcon-Segovia and Khan criteria for MCTD the age-adjusted prevalence was 1.28 (95% CI 0.72-2.09) per 100,000 but the incidence estimate was too small to calculate, Table 1. Using our definition of a diagnosis of MCTD and no other diagnosis of another CTD yielded an age-adjusted prevalence and incidence of MCTD of 2.98 (95% CI 2.10-4.11) per 100,000 and 0.39 (CI 0.22-0.64) per 100,000, respectively, Table 1. Finally, the age-adjusted prevalence and incidence were highest when using a diagnosis of MCTD regardless of other CTD diagnoses found in the charts and were 16.22 (CI 14.00-18.43) per 100,000 and 1.90 (CI 1.49-2.39) per 100,000 respectively, Table 1.

Conclusion: The MLSP allowed us to estimate prevalence and incidence of MCTD in a diverse population. The variation in estimates using both restrictive and liberal case definitions is reflective of the challenges of studying MCTD where the diagnosis is frequently used alongside other CTD diagnoses.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/population-based-prevalence-and-incidence-of-mixed-connective-tissue-disease-from-the-manhattan-lupus-surveillance-program/