Evaluation of the MSMR Surveillance Case Definition for Incident Cases of Hepatitis C

The validity of military hepatitis C virus (HCV) surveillance data is uncertain due to the potential for misclassification introduced when using administra-tive databases for surveillance purposes. The objectives of this study were to assess the validity of the surveillance case definition used by the Medical Surveillance Monthly Report (MSMR) for HCV, the over and underestimation of cases from surveillance data, and the true burden of HCV disease in the U.S. military. This was a validation study of all potential HCV cases in the active component U.S. military from calendar year 2019 obtained using several dif-ferent data sources: 1) outpatient, inpatient, and reportable medical event (RME) records in the Defense Medical Surveillance System, 2) Health Level 7 (HL7) laboratory data obtained from the Navy Marine Corps Public Health Center, and 3) chart review of the electronic medical records of all potential HCV cases, to include those from privately-sourced care. The sensitivity of the MSMR case definition was 83.6% and the positive predictive value (PPV) was 60.0%. This study suggests that the U.S. military should have confidence that the previous estimates derived using the MSMR surveillance case definition were moderately close to the true burden of incident chronic HCV infection (the true incidence of chronic disease being about 27% lower), but these reports likely dramatically overestimate the incidence of acute HCV. Since HCV was selected as an RME to guide public health action, it is most suitable to invest public health efforts in strengthening the use of confirmed RMEs as the surveillance case definition.