Bronchoalveolar lavage.

In formulating a reasonable position about the clinical use of BAL and its analysis, one must acknowledge that it is still an experimental procedure that needs further assessment, and it must continue to be included as part of patient research protocols. Therefore, neither the patient nor his/her insurance carrier should foot the bill, yet. The cost involved in analysis of BAL fluid and serum raises another consideration about how many things need to be measured and what tests give the essential information and are the most discriminating. Clearly, all of the assays suggested by some of the BAL results given in table 2 are not necessary. The cell count and the differential count, indicating the relative percentage of lymphocytes among the respiratory cells, and monoclonal antibody staining to distinguish the various T-cell subtypes give most of the essential cell information that relates to activity of alveolitis and to diagnosis in the interstitial lung diseases. Finding a very high percentage of lymphocytes in BAL fluid shifts the differential diagnosis in an unknown diffuse interstitial lung disease to the possibility of a granulomatous process, especially sarcoidosis or hypersensitivity pneumonitis; whereas elevated PMN with about 3% eosinophils also present suggests possible idiopathic pulmonary fibrosis. Many of the protein and enzyme assays have a role in describing immunopathogenesis, but are rarely measured until a few days after the procedure. Some quite sophisticated cell mediators can be measured, such as interleukin-2 produced by helper T-lymphocytes and many macrophage effector substances that may give more precise information than just cell counts and various immunoglobulin values. These assays require complex biochemical and cell culture work and are only available in special research laboratories, limiting the availability of such tests. Thus, it is not easy to suggest just what tests should be conducted with BAL cells and fluid to tailor costs yet give comprehensive clinical information, too. The use of BAL to obtain cells and proteins lining the alveolar space in many ways is still in its infancy, and new applications are being sought for a substantial list of lung diseases. Just the tip of the iceberg has been investigated, and much more may remain to be uncovered.