Record linkage between hospital discharges and mortality registries for motor neuron disease case ascertainment for the Spanish National Rare Diseases Registry.

Our objective was to analyse the coverage of hospital discharge data and the mortality registry (MR) of La Rioja to ascertain motor neuron disease (MND) cases to be included in the Spanish National Rare Diseases Registry. MND cases that occurred in La Rioja during the period 1996-2011 were selected from hospital discharge data and the MR by means of the International Classification of Diseases. Review of the medical histories was carried out to confirm the causes of death reported. Characteristics of the population with MND were analysed. A total of 133 patients with MND were detected in La Rioja during the period 1996-2011; 30.1% were only recorded in the hospital discharges data, 12.0% only in the MR, and 57.9% were recorded by both databases. Medical records revealed a miscoding of patients who had been diagnosed with progressive supranuclear palsy but were recorded in the MR with an MND code. In conclusion, the hospital discharges data and the MR appear to be complementary and are valuable databases for the Spanish National Rare Diseases Registry when MNDs are properly codified. Nevertheless, it would be advisable to corroborate the validity of the MR as data source since the miscoding of progressive supranuclear palsy has been corrected.