Albumin is not suitable as a marker of bronchoalveolar lavage dilution in interstitial lung disease.

We have investigated the origin of raised bronchoalveolar lavage (BAL) albumin levels in interstitial lung diseases (ILDs), and the hypothesis that acute flux during BAL might contribute to the elevated levels of albumin in samples from ILD patients. Total albumin concentrations were measured in three separately aspirated 60 mL aliquots of BAL in 12 ILD patients and seven control subjects, and previous work indicating that BAL albumin levels may be raised in ILD was confirmed. In addition, the extent of acute flux from the circulation was investigated using 1.48 MBq of 125I-radiolabelled human serum albumin injected intravenously shortly before the procedure. It was found that acute albumin flux occurred in only a minority of the ILD patients (4 out of 12) and control subjects (3 out of 7). These results indicate that the elevated levels of plasma proteins, such as albumin, documented in BAL aspirates from ILD patients are not an artefact of the BAL procedure related to increased vascular permeability, and that this finding is more likely to be related to the effects of chronic inflammatory changes in the lung due to the underlying disease. The work confirms that albumin is unsuitable as a denominator for the normalization of bronchoalveolar lavage solute results, since levels can vary, both as a result of acute flux and, more frequently, because of disease activity.