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

• Published in: Clinical biochemistry Vol. 37; no. 2; pp. 105 - 111
• Main Authors: Comper, Wayne D, Jerums, George, Osicka, Tanya M
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-02-2004
• Subjects: Albumins - metabolism; Albuminuria - urine; Chemistry, Clinical - methods; Chromatography, High Pressure Liquid - methods; Diabetic Nephropathies - diagnosis; Diabetic Nephropathies - urine; Diabetic nephropathy; Female; High-performance liquid chromatography; Humans; Immunoassay - methods; Immunoassays; Male; Microalbuminuria; Regression Analysis; Reproducibility of Results; Sensitivity and Specificity; Urinary albumin; Diabetic nephropathy; Urinary albumin; High-performance liquid chromatography; Microalbuminuria; Immunoassays
• ISSN: 0009-9120; 1873-2933
• DOI: 10.1016/j.clinbiochem.2003.10.008

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°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 × 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.