Hypersensitivity Pneumonitis Diagnosis in ILD: Questionnaires vs Serum IgG Testing

When evaluating a patient with newly identified interstitial lung disease (ILD), using a questionnaire may help clinicians identify potentially relevant exposures for hypersensitivity pneumonitis (HP), according to study results published in the Annals of the American Thoracic Society.

A thorough assessment of environmental exposures is a necessary part of the diagnostic evaluation for HP; however, there is a need for a consensus diagnostic approach. Questionnaires and serum immunoglobulin G (IgG) testing are methods to identify potentially causative exposures, but the amount of evidence to support either method is unknown. Therefore, researchers performed a systematic review to determine the usefulness of these methods in identifying exposures that may have caused HP in patients with ILD.

Researchers identified 1141 and 926 potentially relevant articles for questionnaires and serum IgG testing, respectively; reviewed the full texts of 32 and 49 articles, respectively; and selected 2 observational studies for questionnaires and 15 observational studies for serum IgG testing.

Questionnaires were more accurate for detecting potentially relevant exposures compared with clinical history (100% vs 26%) and serum IgG testing (100% vs 63%), but were not different compared with serum IgG plus bronchial challenge testing (59% vs 65%). In addition, longer, detailed questionnaires were more likely to identify potential exposures, and that 70% of potential exposures identified by questionnaires were subsequently confirmed by environmental testing. Serum IgG testing, conversely, distinguished HP from healthy exposed and unexposed control individuals with high sensitivity (90% and 92%, respectively) and high specificity (91% and 100%, respectively), but did not distinguish HP as effectively from other types of ILD (sensitivity, 83% and specificity, 68%).

“Utilization of a questionnaire to obtain an environmental and occupational history and serum IgG testing are insufficient to definitively distinguish HP from other ILDs,” concluded the study authors. “However, it may influence diagnostic evaluation by providing evidence supportive of HP and management by prompting removal of the exposure from the patient’s environment.”

Reference

Jenkins AR, Chua A, Chami H, et al. Questionnaires or serum IgG testing in the diagnosis of hypersensitivity pneumonitis among patients with interstitial lung disease. Ann Am Thorac Soc. Published online August 11, 2020. doi:10.1513/annalsats.202005-419oc