RELIABILITY OF HOSPITAL DATA FOR POPULATION-BASED STUDIES OF AIR-POLLUTION

The use of hospital databases for research into the respiratory effect s of air pollution has been questioned. In an attempt to address that issue, reabstracts of 1 279 discharge records from 14 Montreal hospita ls were compared with the universal health insurance database of Quebe c. Agreement levels on discharge diagnoses were 94.9% for asthma; 75.5 % for all other respiratory diagnoses combined, including upper airway infections, pneumonia, and coronary obstructive pulmonary disease (CO PD) (90% after ignoring disagreements be tween closely related respira tory diagnoses); and 93.1% for a nonrespiratory comparison group. Fact ors associated with misclassification included use of nonurgent admiss ions; delays in hospital admission from emergency rooms; and differenc es in levels of diagnostic agreement between hospitals, age groups, an d outcome groups. These should be taken into account in air pollution epidemiologic research in which databases of the kind commonly maintai ned in North American health care systems are used.