Exposure Assessment Tools for Hypersensitivity Pneumonitis. An Official American Thoracic Society Workshop Report

Abstract

This report is based on proceedings from the Exposure Assessment Tools for Hypersensitivity Pneumonitis (HP) Workshop, sponsored by the American Thoracic Society, that took place on May 18, 2019, in Dallas, Texas. The workshop was initiated by members from the Environmental, Occupational, and Population Health and Clinical Problems Assemblies of the American Thoracic Society. Participants included international experts from pulmonary medicine, occupational medicine, radiology, pathology, and exposure science. The meeting objectives were to 1) define currently available tools for exposure assessment in evaluation of HP, 2) describe the evidence base supporting the role for these exposure assessment tools in HP evaluation, 3) identify limitations and barriers to each tool's implementation in clinical practice, 4) determine which exposure assessment tools demonstrate the best performance characteristics and applicability, and 5) identify research needs for improving exposure assessment tools for HP. Specific discussion topics included history-taking and exposure questionnaires, antigen avoidance, environmental assessment, specific inhalational challenge, serum-specific IgG testing, skin testing, lymphocyte proliferation testing, and a multidisciplinary team approach. Priorities for research in this area were identified.

Keywords: exposure assessment; extrinsic allergic alveolitis; hypersensitivity pneumonitis; interstitial lung disease; pulmonary fibrosis.

Figure 1.

Conceptual framework describing how exposure identification and sensitization tests impact pretest probability of hypersensitivity pneumonitis (HP). Identification of plausible antigen(s) for HP will determine the pretest probability of disease. The likelihood ratio is determined by other aspects of the clinical assessment for suspected HP. Numbers are for example only. The black line indicates no compelling exposure by history; this is the lowest pretest and post hoc test probability of HP. The red line indicates a less-compelling exposure history (e.g., mold in bathroom) and shows a negative serum-specific immunoglobulin G (SS-IgG) test result. The green line indicates a less compelling exposure history (e.g., mold) and shows a positive SS-IgG test result. The blue line indicates identification of a compelling exposure (e.g., pigeons/farming) with no further testing needed. prob. = probability.