Positive predictive value of mpox diagnoses in French emergency departments: a retrospective validation study using the OSCOUR network.

OBJECTIVE: This study aims to evaluate the positive predictive value (PPV) of clinical mpox diagnoses in the French OSCOUR emergency department (ED) surveillance network in the early phase of the 2022 epidemic. DESIGN: Retrospective observational study. SETTING: EDs across France contributing to the OSCOUR network (over 700 participating EDs covering 97% of national visits). PARTICIPANTS: A total of 531 mpox-related ED visits, identified through clinical diagnoses coded using International Classification of Diseases, 10th Revision (ICD-10), were extracted from the OSCOUR database between May and July 2022. After investigation, we found the accompanying PCR test results for 243 of these cases and they were included in the PPV analysis. OUTCOME MEASURES: The primary outcome was the PPV of clinical mpox diagnoses compared with PCR-confirmed mpox cases. Secondary outcomes were PPV stratified by age, geographical location (Greater Paris vs another region), time of admission, sex and time period. RESULTS: Of the 243 cases with available PCR test results, 175 were confirmed positive and 68 were negative. The overall PPV was 0.72 (95% CI: 0.66 to 0.77). Differences in PPV were observed by sex (F: 0.14 (0.05-0.35); M: 0.77 (0.72-0.82)), age (Less than 30: 0.67 (0.56-0.76), 30-49: 0.83 (0.76-0.88), 50+: 0.33 (0.18-0.53)), geographical location (Greater Paris: 0.77 (0.70-0.82) and other regions: 0.59 (0.46-0.70)). CONCLUSION: Our findings show that overall, the OSCOUR network has a PPV of 0.72 for identifying mpox cases based on ICD-10 coding during the early phase of the 2022 epidemic. These results suggest that this system can be useful when tracking the beginning of emerging health threats.