HDCN Article Review/Hyperlink

Joseph R, Tria L, Mossey RT, Bellucci AG, Maiiloux LU, Vernace MA, Miller I, Wilkes BM

Comparison of methods for measuring albumin in peritoneal and hemodialysis patients

Am J Kidney Dis (Apr) 27:566-571 1996

This paper compares different ways of measuring albumin in hemodialysis patients and CAPD patients. The bromcresol green method was introduced in 1965 and was previously the method of choice. Bromcresol purple was developed to avoid interfering proteins which could artificially elevate the albumin concentration. Nephelometry utilizes a anti-human albumin antibody, and is felt to be more specific, but is more expensive, requires special equipment and can not be done in turbid plasma.

In CAPD patients mean plasma albumin measurements with bromcresol green and nephelometry gave identical results, while bromcresol purple gave about 10% lower readings (38.5 +/- 0.8 g/L v 38.0 +/- 1.0 v 34.6 +/- 0.9); this was true across the entire range of albumin values. In hemodialysis patients, although mean bromcresol green and nephelometry values were the same (40.4 +/- 0.5 g/L v 38.8 +/- 0.5; P=NS), Fisher's exact test showed that bromcresol green caused a slight (4%) overestimate of albumin levels. Bromcresol purple gave about 20% lower albumin levels (32.7 /- 0.4 g/L) compared with both nephelometry and with bromcresol green in hemodialysis patients. The smaller difference between bromcresol purple albumin and the other methods in CAPD compared with hemodialysis patients may be due to fewer interfering substances in the plasma of CAPD patients.

Interestingly, the albumin levels were the same comparing CAPD and hemodialysis patients, when overall levels were assessed (bromcresol green albumin was lower in CAPD patients, bromcresol purple lower in hemodialysis patients, and nephelometry the same in both). This finding differs from other studies which purportedly show lower albumin levels in CAPD patients.

Comment: Because albumin levels are known to correlate closely with mortality levels in hemodialysis and peritoneal dialysis patients, and low albumin is being targeted by regulatory agencies as an indicator of quality of ESRD care, it is critical that albumin levels be measured accurately and consistently. Bromcresol purple consistently gives lower albumin readings in both CAPD and hemodialysis patients, although the magnitude of the reduction was greater in hemodialysis patients. The method-induced variability must be taken into account when regulatory agencies set guidelines, and when clinicians assess the nutritional status of their patients. (Stephen Pastan, M.D., Emory Clinic)