Quantification of the difference between pre-dialysis and post-dialysis serum albumin measurement and its relationship to intra-dialytic weight gain

Abstract

Haemodialysis patients may have low albumin levels due to a cascade of factors, including inflammation and reduced dietary intake. Albumin is commonly used in clinical settings by dieticians as part of a comprehensive nutritional assessment. Presently many dietetic practitioners use interchangeably pre-dialysis and post-dialysis biochemical measurements for albumin. The aim of this study was to quantify the difference between pre-dialysis and post-dialysis serum albumin measurement and its relationship to intra-dialytic weight gain. Fourty-six stable (21 Australian indigenous, 25 non-indigenous) haemodialysis patients were enrolled in a three month cross-sectional study. During the study patients underwent routine haemodialysis treatment and biochemical tests. Weight and biochemical measurements were collected pre and post dialysis on the first Tuesday or Wednesday of each month. A patient generated subjective global assessment (PG-SGA) was conducted in the third month of the study. The incidence of low albumin levels (<35g/L) was 56% (n=26) when serum albumin was measured pre-dialysis, this was reduced to 30% (n=14) when measured post-dialysis. Analysis of serum albumin found a 2.6g/L (CI 1.7-3.5) difference in concentration between pre and post dialysis measurements (p=0.000), with serum albumin less concentrated in pre-dialysis blood samples. Intra-dialytic weight gain (2.0kg, CI 1.7-2.3) correlated with the change in serum albumin (r= 0.464, p=0.001). Intra-dialytic weight gain and the difference between pre and post dialysis serum albumin was greater in Australian indigenous patients than in non-indigenous patients. PG-SGA score was more strongly correlated with post-dialysis than pre-dialysis serum albumin (r=0.430, p=0.003; r=0.389, p=0.008 respectively).This study indicates that measurement of serum albumin should be undertaken post-dialysis when using the measurement as part of a nutritional assessment. Pre-dialysis serum albumin measurement may falsely indicate poor nutritional status, and should be followed with a post-dialysis measurement to confirm finding.