Positive Predictive Values of Familial Hypercholesterolemia Diagnoses in the Danish National Patient Registry and the Danish Familial Hypercholesterolemia Registry - A Validation Study.

The Danish Familial Hypercholesterolemia (FH) Registry (DFH) was established in 2020 to monitor the detection rate of FH and quality of care provided among patients with FH. DFH is nationwide, and together with the Danish National Patient Registry (DNPR) includes more than 10,000 registered cases of FH. However, the validity of FH diagnoses in the DNPR and DFH is unknown. We aimed to investigate the positive predictive value of FH cases registered in the DNPR and DFH. We retrospectively retrieved a nationwide random sample of 800 patients with an FH diagnosis registered in the DNPR between 1st of January 2020 and 1st of May 2023. Subsequently, we retrieved information on cases also registered in the DFH, and validated all registered cases based on medical records. Individuals with a Dutch Lipid Clinical Network-score ≥ 6 were considered valid FH cases. Positive predictive values with 95% confidence intervals were used to assess the validity of the registered diagnoses. We found a positive predictive value of 63.8% (95% CI: 60.7; 67.0) for an FH diagnosis recorded in the DNPR (510/800), and 88.1% (95% CI: 82.2; 92.3%) for those diagnosed with genetic FH (141/160). A primary diagnosis of FH registered by cardiological departments had a positive predictive value of 71.0% (95% CI: 67.2; 74.6%) (417/587), and 88.3% (95% CI: 82.6; 92.8%) for genetic FH (113/128), respectively. The positive predictive value of FH cases registered in the DFH was 83.0% (95% CI: 78.9; 86.5) (318/383). The validity of FH cases in the DFH was high, while the validity of an FH diagnosis in the DNPR was relatively low. However, restricting the analysis to a primary diagnosis obtained from cardiological departments may be used to improve the validity of FH diagnoses in the DNPR.