Questionnaires or Serum IgG Testing in the Diagnosis of Hypersensitivity Pneumonitis among Patients with Interstitial Lung Disease

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Ann Am Thorac Soc


RATIONALE: Hypersensitivity Pneumonitis (HP) results from exposure to a variety of stimuli, which are challenging to identify. Questionnaires and serum IgG testing are methods to identify potentially causative exposures.

OBJECTIVE: To perform a systematic review to determine the usefulness of questionnaires and serum IgG testing in identifying exposures that may have caused HP.

METHODS: This systematic review informed an international, multi-disciplinary panel that developed a clinical practice guideline on the diagnosis of HP for the American Thoracic Society (ATS), Japanese Respiratory Society (JRS), and Asociación Latinoamericana del Tórax (ALAT). MEDLINE, the Cochrane Library, and EMBASE were searched from January 1946 through October 2019 for studies that utilized a questionnaire or serum IgG testing to identify exposures that may have caused HP. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach was used to appraise the quality of the evidence.

RESULTS: Searches identified 1,141 and 926 potentially relevant articles for questionnaires and serum IgG testing, respectively. The full texts of 32 and 49 articles, respectively, were reviewed. Two observational studies for questionnaires and 17 observational studies for serum IgG testing were selected. Questionnaires were better at detecting potentially relevant exposures compared to clinical history (100% vs. 26%, RR 3.80, 95% CI 1.79-8.06) and serum IgG testing (100% vs. 63%, RR 1.58, 95% CI 1.12-2.23), but were not different compared to serum IgG plus bronchial challenge testing (59% vs. 65%, RR 0.90, 95% CI 0.65-1.24). Longer, detailed questionnaires were more likely to identify potential exposures. Only 70% of potential exposures identified by questionnaires were subsequently confirmed by environmental testing. Serum IgG testing distinguished HP from healthy exposed and unexposed controls with high sensitivity (90% and 92% respectively) and high specificity (91% and 100% respectively) but did not distinguish HP as effectively from interstitial lung diseases (sensitivity 83% and specificity 68%).

CONCLUSION: Using a questionnaire may help clinicians identify potentially relevant exposures when evaluating a patient with newly identified ILD for HP. Serum IgG testing may also identify potentially relevant exposures, but it is poor at distinguishing HP from other types of ILD.

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ePub ahead of print