Development and validation of a case definition to identify hemophilia in administrative data

Introduction: Administrative data is useful in population-based studies in hemophilia, but few studies validated the coding accuracy.

Aim: We validated the accuracy of a case definition using a combination of International Classification of Diseases diagnostic codes and coagulation factor level for identifying hemophilia in administrative data.

Methods: This is a retrospective population-based study of all residents of Alberta, Canada, who underwent testing for coagulation factor VIII (FVIII) or factor IX (FIX) activity between 2009 and 2017 using linked administrative data. Our predefined algorithm was a combination of the relevant ICD codes and FVIII/FIX activity <0.4 IU/ml. Medical charts of 2114 randomly selected patients tested for FVIII and 528 patients tested for FIX were reviewed to identify physician diagnoses of hemophilia. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) were calculated.

Results: With our algorithm, 72 (3.4%) patients tested for FVIII and 21 (4.0%) tested for FIX met the combined ICD code and laboratory criteria for hemophilia A and hemophilia B, respectively, whereas 63 (3.0%) and 22 (4.2%) had confirmed hemophilia A and hemophilia B upon chart review. Our algorithm had a sensitivity of 93.7% and specificity of 99.4% for identifying hemophilia A, and a sensitivity of 90.9% and specificity of 99.8% for identifying hemophilia B.

Conclusion: This study showed that using a case definition of ICD codes and coagulation factor activities can identify hemophilia in administrative data with very high accuracy and can be used for future research.