Indexing protein determinations in bronchoalveolar lavage fluids to a reference substance. Value of alveolar potassium

It is well known that a reference substance is required to determine accurately the protein content of broncho alveolar lavage but there has been disagreement as to the ideal reference substance. We studied the relative usefulness and reproductibility of potassium and albumin as reference substances in determining protein content in 8 normal subjects and 10 patients with stage 11 sarcoidosis or extrinsic allergic alveolitis. Two successive lavages were performed intentionally using different volumes of injected normal saline. The use of potassium as a reference substance not only permitted a better reproductibility in determination of protein content of sequential broncho-alveolar lavages but also a significantly better discrimination between normal and abnormal subjects.