Inpatient burden and resource utilization of polymyositis and dermatomyositis: A 10-year Study of National Inpatient Sample.

OBJECTIVES

To characterize inpatient prevalence and resource utilization of patients with polymyositis (PM) and dermatomyositis (DM).

METHODS

Patients with PM/DM were identified from the Nationwide Inpatient Sample (NIS) database from the year 2005 to 2014 using ICD-9 diagnostic codes. The primary outcome of this study was inpatient prevalence of PM/DM in the United States across the span of 10 years. Secondary outcomes included reason for hospitalization, inpatient mortality, morbidity, hospital length of stay (LOS), utilization of specialized procedures/tests and expenditures. A cohort of patients without PM/DM was also identified from the same database to serve as comparators. Multivariate regression analysis was used to adjust for age, sex, ethnicity, comorbidities and hospital characteristics.

RESULTS

A total of 160,528 admissions of patients with a diagnosis of PM/DM occurred in the study period, corresponding to the inpatient prevalence of 41.9 cases per 100,000 discharges. During admission, patients with PM/DM died more frequently than patients without PM/DM with an adjusted odds ratio (aOR) of 2.22 (P<0.01). A significantly higher inpatient morbidity among patients with PM/DM was also observed as indicated by a significantly higher risk of shock (aOR 2.33; P<0.01), acute kidney injury (aOR 1.12; P<0.01), multi-organ failure (aOR 1.83; P<0.01) and need for admission to intensive care unit (aOR 1.94; P<0.01). Patients in the PM/DM had an average of 1.7 more days of LOS (P<0.01). The mean hospital costs and total hospitalization charges for patients with PM/DM were significantly higher than patients without PM/DM with additional adjusted mean of $4,217 and $13,531, respectively, in the multivariate model. Patients with PM/DM underwent computerized tomography scan (aOR 1.90; P<0.01), magnetic resonance imaging (aOR 1.68; P<0.01) and angiography (aOR 1.15; P<0.01) more often than comparators.

CONCLUSIONS

Inpatient prevalence of PM/DM was higher than what would be expected from the overall incidence. Hospitalizations of patients with PM/DM were associated with significantly higher rate of mortality, morbidity and resource utilization.