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

Abstract

BackgroundThe role of bronchoalveolar lavage fluid (BAL) lymphocyte% to diagnose chronic hypersensitivity pneumonitis (CHP) is unclear. We conducted a systematic review and meta-analysis of BAL lymphocyte% in the diagnosis of CHP.MethodsWe searched Medline, Embase and Cochrane library from inception to August 2019. Individual patient data were obtained to test performance characteristics of BAL lymphocyte% at different thresholds. Random-effects models were used for pooled estimates, with comparisons made between CHP and non-CHP interstitial lung diseases (ILD).ResultsFifty-three studies were included in the systematic review and 42 in the meta-analysis. The pooled estimate for BAL lymphocyte% was 42.8% (95%CI 37.7–47.8, I2=95.3%) in CHP, 10.0% (95%CI 6.9–13.1, I2=91.2%) in idiopathic pulmonary fibrosis (IPF), 23.1% (95% CI 3.0–43.2, I2=85.2%) in non-IPF idiopathic interstitial pneumonia (IIP), 23.4% (95%CI 11.0–35.9, I2=45.7%) in connective-tissue disease ILD (CTD-ILD), and 31.2% (95% CI 17.6–44.8, I2=95.2%) in sarcoidosis. Results differed between CHP and IPF (p<0.0001), non-IPF IIP (p=0.0309), and CTD-ILD (p=0.0824), but not between sarcoidosis (p=0.0966). Using individual patient data from eight studies, lymphocyte% threshold >20% provided sensitivity of 68.1% and specificity of 64.8% for CHP. Higher thresholds provided lower sensitivity with higher specificity. Older age and ever having smoked were associated with lower lymphocyte% in CHP.ConclusionsBAL lymphocyte% is higher in CHP compared to IPF and other IIP, with higher thresholds providing improved specificity at the cost of sensitivity. However, parent studies are at risk of incorporation bias, and prospective studies should evaluate the additive discriminate value of BAL lymphocyte% to accurately diagnose CHP.

Diagnosis and Evaluation of Hypersensitivity Pneumonitis

“…A recent meta-analysis evaluated the performance characteristics of BAL at different lymphocyte % thresholds to discriminate chronic HP from nonchronic HP ILDs or IPF/idiopathic interstitial pneumonia, using individual patient data. 121 If the cutoff level of BAL lymphocyte percentage was set low at 20%, the trade-off is a PPV of 41% (95% CI, [37][38][39][40][41][42][43][44] and 57% (95% CI, [52][53][54][55][56][57][58][59][60][61][62] in suggesting chronic HP vs nonchronic HP ILD and IPF/idiopathic interstitial pneumonia, respectively. On the other hand, if the cutoff level was set high at 50%, more subjects with chronic HP would be captured minimizing false-positives (PPV increases to 60% [95% CI, [51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] and 78% [95% CI, [68][69][70][71][72][73]…”

Propionibacterium acnes-associated sarcoidosis complicated by acute bird-related hypersensitivity pneumonitis

“…The differential diagnosis between sarcoidosis and HP with only the limited evidence provided BALF analysis and biomarkers [ 14 – 17 ] can be challenging, although some of these biomarkers are correlated with radiological and immunological features. This report describes for the first time a case of sarcoidosis complicated by acute bird-related HP in which two distinct types of granuloma were successfully distinguished by IHC using PAB antibody.…”

Biomarkers in Progressive Fibrosing Interstitial Lung Disease: Optimizing Diagnosis, Prognosis, and Treatment Response

“…Bronchoalveolar lavage (BAL) has a long and controversial history in the evaluation of ILD ( 178 , 179 ). Its primary use remains discriminating CHP from other forms of ILD, which is supported by elevated lymphocyte count ( 180 ). Accordingly, BAL with cellular analysis is now formally recommended to assist in the diagnosis of CHP ( 181 ) and has received a conditional recommendation for excluding other potential ILD causes when diagnosing IPF ( 182 ).…”