41989 Comparison of the performance of published diagnostic criteria for ulcerative pyoderma gangrenosum

Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis with rates of misdiagnosis of up to 20% [1]. Although different criteria (Su, Delphi, and PARACELSUS) have been proposed to facilitate diagnosis [2-4], there is a lack of studies assessing the sensitivity and specificity across all three diagnostic criteria in independent cohorts of both cases and controls. Hence, we systemically evaluated the discriminatory ability of PG diagnostic criteria in a sample of ulcerative PG cases and controls. MEDLINE was searched from January 2000 to April 2022 for case reports of ulcerative PG and known PG mimickers. Cases were included if patients were aged >18, reported biopsy findings, and clinicopathological data was consistent with the diagnosis. Diagnostic performance was assessed with discrimination/calibration statistics using complete case data. We identified 162 cases, including 93 patients with ulcerative PG and 69 with known PG mimickers classified based on published diagnostic categories (vascular occlusive/venous=19, primary infection=16, cancer=16, drug-induced/exogenous tissue injury=7, calciphylaxis=6, and vasculitis=5). Su exhibited the lowest sensitivity (86.21%) and intermediate specificity (69.57%) and area under the receiver operating characteristic curve (AUC, 0.74) for diagnosis of ulcerative PG. Delphi had intermediate sensitivity (88.00%) but the highest specificity (90.48%) and AUC (0.89). PARACELSUS displayed the highest sensitivity (95.89%) but lowest specificity (4.65%) and AUC (0.55). Overall, we showed differing sensitivities and specificities for published diagnostic criteria in cases with histological findings. Prospective studies are needed to assess the discriminatory ability of these diagnostic criteria in better controlled settings and harmonize existing diagnostic criteria for this rare condition.