Comment on: Bronchoalveolar lavage fluid lymphocytosis in chronic hypersensitivity pneumonitis: a systematic review and meta-analysis

Extract

We commend Adderley et al. [1] for their meta-analysis assessing bronchoalveolar lavage fluid (BALF) lymphocytosis in the diagnosis of chronic hypersensitivity pneumonitis. Distinguishing chronic hypersensitivity pneumonitis (cHP) from idiopathic pulmonary fibrosis (IPF) has prognostic and therapeutic implications. Since there are no studies using lung biopsy as the gold standard to answer this question, the authors had to rely on observational studies, some of which used BALF lymphocytosis as a criterion to diagnose cHP. The authors acknowledge that this can cause diagnostic test incorporation bias. Incorporation bias can result in falsely increased estimates of the association between BALF lymphocytosis and cHP, or in biased conclusions that a bronchoalveolar lavage (BAL) lymphocyte count can rule in or rule out cHP. This is because specificity and sensitivity can be affected when the test under study is used as part of the gold standard to diagnose the condition of interest [2].