Serum albumin by dye-binding: bromocresol green or bromocresol purple? The case for conservatism

Pooled patient's serum selected to have a wide range of albumin concentrations was analysed for albumin by bromocresol green with both long and short incubation times and also by bromocresol purple. Total protein, colloid osmotic pressure, calcium and magnesium were also measured. There were strong linear correlations between albumin measured by the three methods. Albumin values by bromocresol green with a short incubation time (1.5 min) averaged 5 g/L higher than those by bromocresol purple at all albumin concentrations. Colloid osmotic pressure correlated less strongly with total protein and with albumin by bromocresol purple than with albumin by the two bromocresol green methods. There were no significant differences between the correlation coefficients of calcium or magnesium with total protein and with albumin measured by the three methods. Bromocresol purple has no advantage over bromocresol green with a short incubation time for the clinical purposes for which albumin is measured: to detect abnormality, monitor change, predict colloid osmotic pressure and adjust calcium and magnesium for abnormal protein concentrations.