Photo Credit: Aree Sarak
The following is a summary of “Validity of diagnosis codes to identify a dermatomyositis cohort from electronic health records,” published in the January 2025 issue of Dermatology by Silberzweig et al.
Dermatomyositis (DM), a rare idiopathic inflammatory myopathy, was understood to cause distinctive skin lesions and myositis, but its study was hampered by limited observational evidence due to small case cohorts.
Researchers conducted a retrospective study to examine the validity of specialist-specific diagnostic coding for DM in an outpatient clinical database.
They identified adults with outpatient encounters between January 1, 2010, and June 30, 2023, at a U.S. regional health system, having ICD-9/-10 codes for DM. A random sample of 156 patients with more than 1 code from a dermatologist or rheumatologist was selected. The primary reference standard was a confirmed DM diagnosis by the treating physician, while the secondary standard was fulfilment of the 2017 European Alliance of Associations for Rheumatology/American College of Rheumatology (EULAR/ACR) criteria for “probable” or “definite” DM. Positive predictive values (PPVs) were calculated with 95% confidence intervals for various case definitions.
The results showed that the median age of eligible patients was 51.5 years, with 81% being female, for diagnoses based on the treating physician’s confirmation, the PPVs for >1 and >2 codes from a dermatologist were 93.2% (95% CI 82.0%-98.3%) and 96.4% (95% CI 82.2%-99.8%), respectively and PPVs for >1 and >2 codes from a rheumatologist were 82.0% (95% CI 77.1%-86.9%) and 85.8% (95% CI 80.6%-91.1%), respectively. Using at least 1 or 2 codes from a rheumatologist or dermatologist, the PPVs were 82.1% (95% CI 77.3%-86.8%) and 85.7% (95% CI 80.7%-90.8%), respectively. The rate of confirmed cases based on the EULAR/ACR criteria ranged from 44.9% to 57.1%.
Investigators concluded that all tested algorithms produced accurate DM case cohorts with high PPV, and studies prioritizing sensitivity might employ more than 1 code from dermatology or rheumatology to identify patients with DM.
