Potential limitations of diagnostic standard codes to distinguish polycythemia vera and secondary erythrocytosis

In a retrospective analysis of medical records in 578 patients who had been evaluated for the presence of erythrocytosis, the ICD code-based diagnostic system led to misidentification in a number of cases. All of these patients had been tested for the JAK2 mutation, and throughout the chart review, the 2016 WHO diagnostic criteria for polycythemia vera (PV) was applied. In 11% of the cases, patients had concurrent diagnosis codes for PV and secondary erythrocytosis (SE), thus representing a problem in accurately representing PV or SE in ICD-based registries.