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
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
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
slight (4%) overestimate of albumin levels. Bromcresol purple gave about
20% lower albumin levels (32.7 /- 0.4 g/L) compared with both nephelometry
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
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)