The hypersensitivity pneumonitis diagnostic index: use of non-invasive testing to diagnose hypersensitivity pneumonitis in metalworkers.

BACKGROUND

Since 1993, several outbreaks of hypersensitivity pneumonitis (HP) have been reported in metalworkers. We report the largest outbreak of HP in metalworkers yet known. It occurred in a Connecticut factory that produces precision parts for the aerospace industry. The workers typically presented with systemic and respiratory problems ("sick fatigue," myalgias, cough, dyspnea, wheezing, and chest tightness). They had variable findings on clinical tests, which complicated diagnosis. An HP diagnostic index was developed to help reduce the uncertainties in case identification.

METHODS

Data from 16 biopsy-confirmed cases and 14 non-HP patients were compared, and the HP diagnostic index was derived using variables that best discriminated between the two groups. The index is based on (a) work-related symptoms, (b) dry crackles on auscultation, (c) restrictive spirometry, (d) decreased diffusion capacity and/or increased A-a oxygen gradient, (e) elevated erythrocyte sedimentation rate, (f) abnormal radiographic images, and (g) abnormal gallium scans. We then applied the HP diagnostic index and, for comparison, the "Kenosha epidemiological case criteria" (developed during a recent HP outbreak in an automobile factory) to our data set.

RESULTS

The HP diagnostic index and the Kenosha criteria confirmed HP in overlapping sets of 36 and 34 patients, respectively, that were both in good agreement with the clinical diagnoses.

CONCLUSIONS

The HP diagnostic index relies less heavily on symptoms, subjective evaluations, and invasive tests than the Kenosha criteria, but both identified similar subsets of the 61 patients as having HP. The HP diagnostic index could provide a useful tool in future HP outbreaks, which are increasingly being recognized in metalworking facilities.