Accurate measurement of human serum albumin by bromcresol purple dye-binding

Abstract

The use of Bromcresol Green (BCG) to measure albumin is widespread despite the documented over-estimation by this technique in the clinically important low range. BCG binds to α & β globulins in a time-related manner causing significant over-estimation even at 18 sec after mixing. Bromcresol Purple (BCP) shares the desirable features of dye-binding techniques, yields a stable chromogen, and gives excellent agreement with immuno-chemical measurements of albumin.<mml:math><mml:mrow>Alb <mml:mo>\(</mml:mo>BCP<mml:mo>\)</mml:mo><mml:mo>=</mml:mo><mml:mn>0.95</mml:mn> Alb <mml:mo>\(</mml:mo>RID<mml:mo>\)</mml:mo><mml:mo>+</mml:mo><mml:mn>2.5</mml:mn></mml:mrow></mml:math> The recently published method of Pinnock <i>et al. (Clin. Chem.,</i> 1978,<b>24,</b>80) has been adapted to discrete analysers (Centrifichem 400, ABA-100). The optimized stable reagent and analytical conditions chosen ensure linearity to 60g/L, and excellent precision (CV <2% at 30g/L). However, heparin plasma is unsuitable (turbidity develops) and animal albumin (bovine, equine, porcine) is grossly under-estimated. With these limitations, BCP-binding appears to be the method of choice for the rapid, precise, accurate and economical measurement of human albumin suitable for automated equipment.