IgG antibody testing in the diagnosis of hypersensitivity pneumonitis: A scoping review.

BackgroundDiagnosis of hypersensitivity pneumonitis (HP) or extrinsic allergic alveolitis requires a combination of tests with antibody testing playing a supportive role to identify exposures.ObjectivesWe conducted a scoping review on antibody testing in -related HP to identify the utility and diagnostic cutoffs proposed in the literature. We compared these cutoffs with studies of chronic pulmonary aspergillosis (CPA) and manufacturers' cutoffs.Eligibility criteriaOnly studies addressing the diagnostic value of IgG or precipitins for HP were included. Separately papers defining cutoffs for CPA were tabulated.Sources of evidencePublished papers were identified in literature searches in Embase, Web of Science, and Medline.ResultsWe identified 414 papers, of which 12 were included, all published between 1965 and 2005. Occupational HP linked to spp. exposure included Farmer's Lung, Malt-Worker's Lung, Esparto Worker's Lung, and Woodworker's lung (Sawmill-workers). No studies directly addressed serological testing in Tobacco Worker's lung, Compost Lung, or poultry workers. Among species exposure, was most commonly described; others included (now ), , and . Antibody tests included ELISA, BALISA, precipitin tests and ImmunoCAP, with a higher sensitivity of ELISA and ImmunoCAP tests compared to precipitin tests. Patients with HP linked to exposures, were positive in 156/290 (53.8%) compared to 96/615 (15.6%) in those with similar occupational exposures without HP. In malt workers with HP 35/53 (66%) had detectable IgG antibody compared to 0/53 IgG, and 13/74 (18%) exposed but unaffected workers, but are not commercially available.ConclusionsImproved means of establishing or ruling out exposure are required, given the negative consequences for patients of continued inhalation. Modern studies with commercially available IgG antibody assays are required to define appropriate cutoffs for HP, given numerous studies published for chronic pulmonary aspergillosis.