The impact of bronchoalveolar lavage on the diagnosis of undifferentiated interstitial lung disease alongside a multidisciplinary discussion.

Background and objective: Cellular analysis of bronchoalveolar lavage (BAL) fluid may aid diagnosis in patients with undifferentiated interstitial lung disease (ILD). The utility of this test in the diagnostic process in conjunction with a multidisciplinary discussion (MDD) is not known. We aim to assess and compare interobserver agreement and diagnostic confidence before and after presenting BAL results in an ILD-MDD.

Methods: Patients undergoing investigations for ILD at Waikato Hospital were recruited. At the ILD-MDD two respiratory physicians and one respiratory radiologist participated in the discussion, and their diagnosis and diagnostic confidence were assessed at four sequential time points. Assessors were blinded to each others diagnosis and diagnostic confidence scores. The four sequential time points were (1) after clinical and radiology presentation; (2) after subsequent MDD; (3) after reviewing BAL results; (4) after final MDD with all results. Interobserver agreements were calculated using Fleiss κ statistic.

Results: 36 patients were recruited, and 77.8% were male. In the first step, the interobserver agreement was substantial κ = 0.622 (95% CI 0.47-0.77), improving in step 2 following MDD to κ = 0.78 (95% CI 0.624-0.935), in step 3 κ = 0.776 (95% CI 0.614-0.937) and step 4 achieved almost perfect agreement of κ = 0.969 (95% CI 0.828-1.11). The diagnostic confidence for individual and group diagnosis increased with the presentation of BAL with and without multidisciplinary MDD.

Conclusion: We found that BAL cellular analysis improves interobserver agreement and confidence in diagnosis following MDD, thus aiding decision-making in cases with undifferentiated ILD.