Positive predictive value of ICD-10 diagnosis codes for brain abscess in the Danish National Patient Registry

To evaluate the positive predictive value (PPV) of ICD-10 diagnosis codes for brain abscess in the Danish National Patient Registry (DNPR).

We examined medical records of all patients with a first-time diagnosis code of brain abscess in the DNPR from 2007 to 2016. Patients were categorized with either confirmed or disproved brain abscess using a priori defined criteria. We computed the PPV as the proportion of confirmed diagnoses.

We identified 709 patients, of whom the medical records could not be retrieved for 15 patients, leaving 694 for further analyses. Of these, 444 had a confirmed brain abscess and 250 had another proven diagnosis, including 47 cases of intracranial empyema. The overall PPV was 64% (95% CI: 60-68) ranging from 24% to 96% among the different codes evaluated. By including only patients with either 1) both a diagnosis and surgical procedure code for brain abscess or 2) patients admitted to hospital with certain primary diagnosis codes (DG060[C,E,F] or DG079B) without newly diagnosed central nervous system (CNS) cancer, spondylodiscitis/intraspinal abscess, or procedure codes for evacuation of intracranial empyema, the PPV increased to 84% (95% CI 80-87) and 89% (395/444) of all confirmed cases were identified.

The overall PPV of diagnosis codes for brain abscess in the DNPR was moderate. However, by exclusion of newly diagnosed CNS tumors, spondylodiscitis/intraspinal abscess, and intracranial empyemas, the PPV was high and therefore suitable for future registry-based studies of brain abscess.