Limitations of hospital discharge diagnoses for surveillance of extrinsic allergic alveolitis.

Hospital discharge diagnoses were used to identify all inpatient cases of extrinsic allergic alveolitis (EAA) from 1979 to 1982 in New Jersey. Of 170 reported cases, the hospital records of 48 were available for review. Based on published criteria for the diagnosis of EAA, only three cases (6%) could be classified as probable EAA, while 10 (21%) were possible cases, and 34 (73%) were not EAA. Limitations were apparent in the accuracy of discharge coding and also in the accuracy of the physician's diagnosis. These findings should promote caution among investigators using unvalidated reports based on ICD-9 hospital coding of EAA. Implications for reporting of other occupational lung diseases are discussed.