Validity of hospital discharge diagnoses for the assessment of the prevalence and incidence of amyotrophic lateral sclerosis

Abstract

Introduction As amyotrophic lateral sclerosis (ALS) is a rare neurological disorder, many sources must be investigated for complete case ascertainment. Hospital discharge diagnoses (HDDs) are a source of administrative data for patients hospitalized for a given disease. The accuracy of HDDs was tested, to assess whether they could be used to trace patients with amyotrophic lateral sclerosis (ALS). Methods All the HDDs referring to patients with motor neuron disease (MND) (ICD-9 code 335.2) were identified from primary hospital discharge diagnoses made during the years 1994-95 in six target provinces of the Lombardy region in Northern Italy (total population 2922920). The medical records of the patients were reviewed and each patient was then accepted or rejected according to whether he/she did or did not satisfy the El Escorial criteria for the diagnosis of ALS. The ALS discharge diagnoses filed in the study period in the neurology departments of all the regional hospitals were the 'gold standard'. Newly diagnosed patients registered during the year 1998 in the same provinces served for the calculation of the incidence of the disease. Sensitivity, specificity and positive predictive value were calculated. Data were presented separately for all the patients and those who were indicated as first hospital admissions. Results During the study period a total of 1012122 hospital discharge records were coded in the six index provinces. The ICD-9 code 335.2 was reported in 408 of the…