Validity of diagnostic codes and estimation of prevalence of diabetic foot ulcers using a large electronic medical record database

Aims: To assess the validity of the diagnostic codes relating to diabetic foot ulcer (DFU) in the electronic medical records of a large integrated care provider and to assess the prevalence of DFU among its members. Materials and Methods: Data were obtained from the diabetes registry of Maccabi Healthcare Services (MHS), a 2.1-million-member sick-fund in Israel, which included 125 665 patients in 2015. We randomly selected and reviewed ~400 patient files from each of the following categories during study period: (1) had a diagnostic code of DFU; (2) had a diagnostic code, or clinical condition suggestive of DFU including: leg-ulcer, amputation, DFU in quartiles proximate to 2015 or abnormality reported by nurse; (3) patients at high risk for DFU (age > 35 and one of the following: peripheral artery disease, neuropathy, DFU during 2011-2014, eGFR<30 mL/min/m² or foot deformity). The patients' charts were reviewed by study physicians, and DFU was validated or refuted. Results: Relying upon diagnostic codes entered by physicians, the positive predictive value (PPV) was 73.1% (95% CI 67.6-78.2), and the sensitivity was 48.2% (95% CI 45.8-50.7%). The PPV of the diagnostic codes listed by podiatrists were significantly lower, while that of codes listed by nurses was higher but with lower sensitivity. The estimated annual prevalence of DFU in the diabetes registry of MHS was 1.2% (95%CI 1.0-1.5%). Conclusions: Diagnostic codes alone cannot be used reliably to create a DFU registry. Nevertheless, the data collected provide an estimate of the prevalence of DFU among patients included in the MHS diabetes registry.