Validity of death certificates in the identification of cases of amyotrophic lateral sclerosis (ALS) in the Limousin region, France. A population-based study

Objectives: Mortality data have been used as a proxy for amyotrophic lateral sclerosis (ALS) incidence. However, the accuracy of death certificates (DCs) needs to be validated. This study aims to assess the accuracy of DCs in the identification of ALS cases. Methods: This is a retrospective population-based validation study. DC information, provided by the "Centre d'épidémiologie sur les causes médicales de décès", including ICD10 codes for specific cause of death for patients recorded in the French register of ALS cases in the Limousin region (FRALim) and deceased between 2000 and 2011, was assessed. The FRALim register was used as gold standard. Results: In the study period, DCs were available for 197 patients diagnosed with ALS, of whom 185 (93.9%) were correctly identified with an ICD10 code (G12.2) corresponding to ALS. The overall sensitivity was 93.9% (95% CI 89.6-96.8) and the positive predictive value (PPV) was 64.9 (59.1-70.4), with higher values in the period 2004-2011 (75.0-78.9). Stratification for sex, age, and year at death did not show difference in accuracy, except a lower PPV during the first years of observation. Conclusions: DCs identifying subjects with a diagnosis of ALS in the Limousin region, France showed an overall good sensitivity and moderate PPV. The absence of ALS diagnosis as the main and underlying cause of death on DCs highlights the need to use DC in combination with other administrative data to create algorithms with higher accuracy performances.