Lithium heparinised blood-collection tubes give falsely low albumin results with an automated bromcresol green method in haemodialysis patients

Abstract

The aim of this study was to investigate the cause of markedly low albumin values determined by a bromcresol green (BCG) method in patients on haemodialysis. Serum and heparinised plasma from haemodialysis patients and normal controls were collected. Albumin was measured using Beckman bromcresol purple (BCP) and Roche BCG methods on the Beckman Synchron LX20. The albumin in heparinised plasma determined by a BCG method was 33.3% lower than that of the BCP method in a haemodialysis patient. The albumin values determined by the BCP method were comparable to those measured by immunonephelometric analysis for this patient. Significantly lower albumin levels were also observed in lithium heparin plasma by a BCG method compared to the BCP method in both non-renal patients (31.2+/-3.8 vs. 34.1+/-4.1 g/L, p<0.001, n=30) and haemodialysis patients (28.6+/-3.5 vs. 32.8+/-3.7 g/L, p<0.001, n=30). This negative bias was directly correlated with heparin concentrations in the plasma. The BCP method did not show this dose-dependent bias. Lithium heparin plasma can cause falsely low albumin values by an automated BCG method and the suitability of lithium heparin blood tubes should be carefully assessed for haemodialysis patients. The BCP method is free of this bias.