Determination of trace amounts of albumin in human bronchoalveolar lavage fluids by fluorometry with chromazurol S

Fluorometry using chromazurole S (CAS) was applied to determine trace amounts of albumin in human bronchoalveolar lavage fluids (BALF). The calibration curve was linear in the range of 5–60 μg/ml of albumin. The CAS method was proven to be much more selective for albumin than for IgG. Freezing of BALF samples did not affect albumin analysis by the CAS method after storage at -20°C for 80 days. This finding suggests that albumin in the BALF samples is stable under these conditions. The correlation was highly linear ( r = 0.966) between the albumin levels in concentrated BALF samples ( n = 47) determined by the CAS method and by radial immunodiffusion. The CAS method is sensitive enough to determine albumin levels in unconcentrated BALF samples, whereas radial immunodiffusion often requires concentration. The former method is more suitable for measuring albumin in BALF samples than the latter, because concentration by ultrafiltration results in poor reproducibility. The concentration of albumin in BALF samples of healthy volunteers ( n = 5) and patients with sarcoidosis ( n = 32) was determined by the CAS method. There was a statistically significant difference ( P < 0.01) in the albumin levels in BALF samples between healthy subjects and patients with sarcoidosis at a clinically active state ( n = 15). This finding shows that the determination of albumin levels in BALF samples is useful for investigating lung diseases and that the CAS method is promising in the determination of trace albumin in BALF samples, because it is simple, sensitive and precise.