Original articleValidity of hospital morbidity records for amyotrophic lateral sclerosis: A population-based study
Introduction
Amyotrophic lateral sclerosis (ALS) is a degenerative disorder of adult life, characterized by the involvement of upper and lower motor neurons at bulbar and/or spinal level. The disease is usually fatal within 3 years from onset. Its cause is still unknown, and epidemiological research may be useful in determining etiologic clues for basic and clinical research. However, it is still unclear whether there are significant differences in ALS incidence within and between Western countries, and whether the incidence of the disease is changing over time 1, 2, 3, 4. The best methodology for the analysis of ALS incidence is a prospective, population-based design, with an intensive search for all cases in a defined area. However, this approach is time-consuming and expensive, and, more important, can be performed only in relatively restricted areas and for a limited time period. The diffusion of hospital in-patients statistics raises the possibility of performing studies on large areas with reduced expenses [5]. However, their epidemiologic validity depends on a number of factors, first of all the appropriateness of discharge diagnoses coding.
The aim of the present study was to verify the completeness of cases identified through administrative database and the validity of ALS discharge diagnoses, to assess the feasibility of using hospital records for epidemiologic purposes. Data were compared to those of a population-based study on ALS incidence in an Italian region [4], which was used as gold standard. Moreover, the validity of discharge files was analyzed to identify the main procedures performed on ALS patients.
Section snippets
Identification of ALS incident cases in the population-based ALS Register
On January 1, 1995, the Piemonte and Valle d'Aosta Register for ALS (PARALS) [4] was established with the aim of performing a prospective epidemiologic study of ALS in a large area of Northwestern Italy (population: 4,418,503 inhabitants at the time of the 1991 Italian general census). The results reported in the present survey are referred to the patients incident in the 2-year period 1995–1996. The register was based on the collaboration of all the neurologic departments of the two regions,
Results
Out of a total of 1,658,311 admissions during the years 1995–1996, 1,049 diagnoses reported the code 335.2 (907 as primary diagnosis, 142 as secondary diagnosis). Of these, 322 patients were excluded from the study because they were not resident in Piemonte. Out of the remaining 727 discharges, after excluding 374 repeat admissions, we found 433 persons with the diagnosis 335.2 (309 as primary diagnosis, 124 as secondary diagnosis). After verifying the clinical records of all these patients,
Discussion
Hospital discharge data may be an useful source of data for descriptive epidemiologic studies, for disease surveillance, for evaluating effectiveness of care, and also for surveying occupational diseases and toxic exposures [5]. In Italy, ICD-9 codes (ICD-9-CM from year 2000) for hospital discharge data are becoming increasingly important after the introduction of diagnosis-related groups (DRGs) as system of reimbursement of public hospitals by the Italian National Health System in 1995 [9].
Acknowledgements
We thank the Health Department (Assessorato alla Sanità) of Piemonte Region for allowing access to the Piemonte Hospital Discharge Database.
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Piemonte and Valle d'Aosta Register for ALS (PARALS): Coordinating center: 2nd Division of Neurology, Department of Neuroscience, University of Torino, Italy. Project coordinator: Adriano Chiò. Study monitors: Andrea Calvo, Nicoletta Di Vito, Marco Vercellino, Federica Plano. Scientific Committee: Antonio Bertolotto, Edo Bottacchi, Adriano Chiò, Dario Cocito, Maria Teresa Giordana, Maurizio Leone, Letizia Mazzini, Gabriele Mora. Collaborating centers: Adriano Chiò, Anna Terreni, Davide Schiffer, Roberto Mutani, Dario Cocito, Bruno Bergamasco, Innocenzo Rainero (Department of Neuroscience, Section of Neurology, University of Torino, and Azienda Ospedaliera San Giovanni Battista, Torino), Antonio Bertolotto, Antonella Tribolo, Rossella Sciolla, Fiorella Mondino, Maria Teresa Giordana (Department of Neuroscience, Section of Neurology, University of Torino, and Azienda Ospedaliera San Luigi Gonzaga, Orbassano), Maurizio Leone, Paola Gaviani, Francesco Monaco (Department of Neurology, ‘Amedeo Avogadro’ University, Novara), Marco De Mattei, Enrico Morgando (Department of Neurology, Azienda Ospedaliera San Giovanni, Torino), Luisa Sosso, Maurizio Gionco (Department of Neurology, Ospedale Mauriziano, Torino), Ugo Morino, Marcello Nobili (Department of Neurology, Ospedale Martini, Torino), Lucia Appendino (Department of Neurology, Ospedale Maria Vittoria, Torino), Letizia Mazzini, Domenico Piazza (Department of Neurology, Ospedale S. Giovanni Bosco, Torino), Enrico Oddenino, William Liboni (Department of Neurology, Ospedale Gradenigo, Torino), Giovanna Vaula, Giancarlo Ferrari (Department of Neurology, Ivrea), Maria Favero, Carlo Doriguzzi Bozzo (Department of Neurology, Pinerolo), Paola Santamaria (Department of Neurology, Vercelli), Umberto Massazza, Elisabetta Bollani (Department of Neurology, Biella), Angelo Villani Roberto Conti, (Department of Neurology, Domodossola), Gabriele Mora, Carla Balzarini, (Department of Neurological Rehabilitation, Fondazione S. Maugeri, Clinica del Lavoro e della Riabilitazione, IRCCS, Scientific Institute of Veruno), Mario Palermo (Department of Neurology, Alessandria), Franco Vergnano (Department of Neurology, Casale Monferrato), Susanna Cordera, Carlo Buffa (Department of Neurology, Novi Ligure), Maria Teresa Penza (Department of Neurology, Tortona), Franco Fassio (Department of Neurology, Asti), Piero Meineri (Department of Neurology, Azienda Ospedaliera Santa Croce e Carle, Cuneo), Andrea Cognazzo, Cristina Mocellini, Anna Dutto, Anna Cucatto (Department of Neurology, Savigliano), Cinzia Cavestro, Walter Troni, (Department of Neurology, Alba), Giovanni Corso, Edo Bottacchi (Department of Neurology, Aosta).