Validation of a COPD diagnosis from the Swedish Inpatient Registry

Aims: The Swedish National Inpatient Registry is an important source of data for numerous epidemiological studies, amongst them studies on chronic obstructive pulmonary disease (COPD). General validation studies indicate that in general 85-95% of diagnoses reported are correct, but this is not true for all groups of diseases, why specific validation studies are of great importance. Methods: Charts from 374 individuals discharged with a COPD diagnosis between 2000-07 from two central hospitals and two university hospitals in the county of Skane were validated against the original medical files. Criteria for the degree of certainty of the COPD diagnosis were predefined and the association between predictors of diagnostic probability and the level of certainty was assessed using an ordinal logistic regression model. Results: According to the Global Initiative for Chronic Obstructive Lung Disease criteria, 21.7% of the diagnosis were classified as proven COPD, 35.5% were classified as probable, another 34.0% as possible COPD, 2.1% were classified as having an uncertain diagnosis, and 7.0% as an unlikely COPD diagnosis. Age category (adjusted ORs: 60-79 years, 2.6, 95% CI 1.2-5.4; >= 80 years, 1.6, 95% CI 0.7-3.3) and discharge from a non-surgical department (adjusted OR: 1.7, 95% CI 1.1-2.8) were significantly associated with higher level of diagnostic certainty. Conclusions: A COPD diagnoses from the Swedish Inpatient Registry is of acceptable validity for epidemiological research. The degree of certainty of the diagnosis varies but less than 10% were considered as misclassified or having an uncertain COPD diagnosis.