Prevention of protein adsorption: effect on patient results for microalbuminuria

Adding Triton X-100 to the diluent used for preparation of standard curves for protein assays can prevent non-specific adsorption of proteins from standards with a low protein content. Since results for low urinary albumin concentrations in control samples from different laboratories showed a wide range of mean values, we studied the effect of adding Triton X-100 to the diluent used in the preparation of the standard curve. Adding Triton X-100 resulted in absorbances which were more reproducible for both serum-based and purified-albumin-based standards. Results for control samples were also less variable in the Triton X-100 assay system. In control samples and patient samples the concentration of albumin was significantly lower in the Triton-X-100-based assay system. Adsorption of proteins from standards can only account for a small proportion of the variation in the range of mean results for urinary albumin in control samples from different laboratories.