Influence of protein composition on total urinary protein determined by pyrocatechol‐violet (UPRO vitros) and pyrogallol red dye binding methods

Influence of protein composition on total urinary protein assays was evaluated for pyrogallol red‐molybdate both with and without sodium dodecyl sulfate (SDS) and pyrocatechol violet‐molybdate complex (UPRO) techniques. Using mixtures of albumin and γ‐globulins (n = 8; albumin/globulin ratio, 0 to 10), mean recoveries were 79, 77, and 81% for pyrogallol red, pyrogallol red‐SDS, and UPRO, respectively. Using diluted myeloma sera (n = 26; A/G ratio, 0.39 to 2.35), mean recovery by the UPRO method was 115% (vs. 63% for pyrogallol red and 83% pyrogallol red‐SDS). Results positively correlated with A/G ratio for UPRO (r = 0.69; P < 0.001), pyrogallol red (r = 0.48; P < 0.05), but not pyrogallol red‐SDS (r = 0.191; NS). The difference between UPRO and pyrogallol red assays correlated with the A/G ratio (r = 0.82; P < 0.001). In light chain proteinuria (n = 10), no significant difference (< 15%) was observed between techniques, whereas in glomerular selective proteinuria (n = 10), values were significantly higher with the UPRO assay (2.20 ± 1.61 vs. 1.43 ± 1.10 g/L; P < 0.02). Our results support the idea that screening for renal diseases can be performed with UPRO or pyrogallol red assays. However, since A/G ratios may vary with renal disease evolution, follow‐up of patients with positive proteinuria should be performed using the same assay, preferably the pyrogallol red‐SDS. J. Clin. Lab. Anal. 15:40–42, 2001. © 2001 Wiley‐Liss, Inc.