A population-based study of patients with Wilson’s disease identified in the French national insurance claims database, with a proposal for an exploratory algorithm for improved case identification

Objective To investigate the pertinence of different potential markers for case identification of WD patients in the French National Health Data System (SNDS). Methods Patients in the SNDS with hospitalization or long-term disease (LTD) status associated with a diagnostic code for WD (E83.0) between 2009 and 2019 were identified and followed from first documentation until 31st December 2019 (or death). Four patient groups were compared. Group A: patients hospitalized for WD, but with neither LTD status nor specific WD treatment. Group B: patients with LTD status, but without treatment. Group C: patients with treatment, but without LTD status. Group D: patients with both LTD status and WD treatment. Results 1,520 patients were included (Group A: N = 702; Group B: N = 153; Group C: N = 194; Group D: N = 471). >75% of untreated patients in Groups A and B were never monitored for copper accumulation. The mean number of blood copper tests over the follow-up period was 0.30 ± 2.47 in Group A, 0.76 ± 2.34 in Group B, 3.99 ± 7.66 in Group C and 5.33 ± 7.90 in Group D. Patients in Group A frequently presented LTD status for conditions unrelated to WD, and higher mortality (hazard ratio: 2.87 [95%CI: 1.87–4.41] compared to Group D), frequently dying of causes unrelated to WD. Conclusions For many patients identified only by a hospitalization claim, no specific WD treatments or copper monitoring were ever documented. Substantial doubt exists whether these patients actually had WD. Validation studies are needed to find the optimal diagnostic algorithm to identify WD cases unambiguously, which is a prerequisite for collecting reliable information on WD.