Background and objective: The accuracy of comorbidity data within the Western Australian Data Linkage System was evaluated by means of comparison with hospital charts and a general practitioner (GP) survey.
Methods: Patients (n=2,037) with a hospital admission from 1991 to 1996 were selected. Linked data were extracted for 100 comorbidities, categorized into 16 diagnostic chapters, for each hospital admission within a 5-year period. Clinical chart review and a GP survey were performed. Comorbidity occurrence in each data source and false-positive and false-negative diagnoses were ascertained.
Results: Administrative data contained 45.5% of comorbidity recorded in hospital charts and underascertained secondary conditions for all 16 diagnostic chapters. False-positive diagnoses were low for most conditions (range: 0-1.5%); however, a high occurrence of false negatives existed for all comorbidity chapters (range: 16.3-91.3%). GP-identified comorbidity was 20.0% greater than that found using administrative data but, with the exceptions of injury-poisoning and cutaneous-subcutaneous diseases, was less (42.0%) than that observed from hospital charts.
Conclusion: Our results indicate that when accurate comorbidity data are crucial to health outcome research, hospital chart review (as opposed to using administrative data) may be required. Furthermore, surveying GPs, at least in Australia, appears an unsatisfactory alternative to hospital charts for obtaining retrospective comorbidity information.