Differences in urinary albumin detected by four immunoassays and high-performance liquid chromatography

Clin Biochem. 2004 Feb;37(2):105-11. doi: 10.1016/j.clinbiochem.2003.10.008.

Abstract

Objectives: To compare the analysis of urinary albumin from diabetic patients by four conventional immunoassays including radioimmunoassay (RIA), immunonephelometry (IN), and two different methods of immunoturbidimetry (IT), as well as by high-performance liquid chromatography (HPLC).

Design and methods: Urines were collected over a 24-h period and stored at -20 degrees C until assay. Urinary albumin concentration was determined by an in-house RIA, by IN using a Beckman Array Analyser with reagents from Beckman Diagnostics (Sydney, Australia), by IT using a Dade-Behring Turbitimer with reagents from Dade-Behring (Marburg, Germany), by IT using a Dade-Behring Dimension R x L Chemistry Analyser with reagents from DiaSorin (Stillwater, OK, USA), and by HPLC using a Zorbax Bio series preparative GF-250 column. Regression lines were calculated using a least squares method to determine the correlation between the assays studied. Bland-Altman bias plots including limits of agreement were also calculated.

Results: The correlation coefficients calculated were high (>0.85) indicating a strong linear relationship between all assays studied. The slopes calculated for the comparisons demonstrate that each assay can vary from one another (up to threefold) and have a slope significantly different from an ideal slope of 1 (P < 0.001). These results were confirmed by Bland-Altman bias plots and calculation of the limits of agreement that were all large.

Conclusions: At this time, there is no global standard by which urinary albumin assays may be standardized. This study suggests the need for such standards.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Albumins / metabolism*
  • Albuminuria / urine*
  • Chemistry, Clinical / methods
  • Chromatography, High Pressure Liquid / methods
  • Diabetic Nephropathies / diagnosis*
  • Diabetic Nephropathies / urine
  • Female
  • Humans
  • Immunoassay / methods
  • Male
  • Regression Analysis
  • Reproducibility of Results
  • Sensitivity and Specificity

Substances

  • Albumins