ponceau-s and Proteinuria

Topics: Azo Compounds; Cerebrospinal Fluid Proteins; Coloring Agents; History, 20th Century; Humans; Microchemistry; Proteinuria

Most clinical laboratories replaced their manual precipitation techniques for the determination of urinary protein with automated dye binding assays or benzethonium chloride-turbidimetric assays. Few studies have validated these assays for the measurement of urinary proteins in the normal range.. This study compares four automated assays for the measurement of urinary protein to a manual Ponceau S/TCA precipitation assay. We evaluated the linearity, the precision, the analytical sensitivity, the accuracy and the recovery of different proteins for each assay.. All assays showed good linearity with the theoretical concentration of albumin present in the sample. The coefficient of variation was below 10% at a concentration of 0.142 g/L. However, the manual Ponceau S/TCA assay demonstrated superior analytical sensitivity. Accuracy determinations showed a variable positive bias and poor correlations at concentrations below 0.1 g/L when compared to the Ponceau S/TCA assay. Small molecular weight peptides particularly affected the pyrogallol red assays but other urinary components also interfered with the automated assays.. Most automated assays show high imprecision and poor accuracy for the measurement of urinary protein in the normal range. The Ponceau S/TCA offers a precise and accurate manual alternative to these automated assays.

Topics: Albuminuria; Artifacts; Autoanalysis; Azo Compounds; Calibration; Coloring Agents; Diagnostic Errors; gamma-Globulins; Humans; Mucoproteins; Peptides; Proteinuria; Reproducibility of Results; Sensitivity and Specificity; Serum Albumin; Uromodulin

We determined total blood protein (TBP) and total urine protein (TUP) in healthy subjects and urolithiasis (UL) patients with renal calculi of different chemical composition: phosphate (CaP), oxalate (CaOx) and urate (HUr). We discussed the peculiarities of TBP and TUP distribution curves obtained and showed that the data on TBP and TUP do not make it possible to reliably single out patients with UL or determine the chemical composition of calculi in their kidneys. However, it was established that the comparison of TUP measurement results for UL patients using the Ponseau-S and sulfosalicylic acid methods makes it possible to reliably separate patients with Ca-containing calculi (CaP and CaOx) from those with HUr calculi. The explanation to this phenomenon using the data on the fractional composition of TUP and the organic matrix of those patients' calculi is given.

Topics: Azo Compounds; Benzenesulfonates; Blood Proteins; Coloring Agents; Humans; Kidney Calculi; Oxalates; Phosphates; Proteinuria; Salicylates; Solvents; Uric Acid

Four commonly used methods for the determination of total protein in urine were compared. These were two biuret methods using different precipitants, a Ponceau S method and a Coomassie Brilliant Blue method. The protein content of the urines was also evaluated by sodium dodecylsulphate polyacrylamide gel electrophoresis. The biuret method with ethanolic phosphotungstic acid as precipitant correlated best with the Coomassie Brilliant Blue method (r = 0.944; p less than 0.001) but less well with the Ponceau S (r = 0.895; p less than 0.001) or biuret-trichloroacetic acid (r = 0.874; p less than 0.001) methods. For urines with normal electrophoretic protein patterns, the imprecise biuret-trichloroacetic acid method (cv = 18.5%) gave the greatest number of false high results (23 in 36 urines) as assessed by electrophoresis. False low results were common in low relative molecular mass (Mr) proteinuria, especially with the biuret-tricholoroacetic acid and Ponceau S methods. High Mr proteinuria rarely caused false low results. Discrepancies between methods appear to have resulted from incomplete precipitation of low Mr protein by trichloroacetic acid.

Topics: Azo Compounds; Biuret Reaction; Chemical Precipitation; Coloring Agents; Electrophoresis, Polyacrylamide Gel; Humans; Molecular Weight; Proteinuria; Reproducibility of Results; Rosaniline Dyes; Silver; Staining and Labeling

Total urine protein was measured in 132 samples by an automated benzethonium chloride method and the Ponceau-S/trichloroacetic acid (PS/TCA) method. Of these, 27% gave a result 0.1 g/L or more higher by the benzethonium chloride method. Of this 27%, most contained an abnormally high concentration of the acute-phase reactant, alpha 1-acid glycoprotein. By assaying urine containing added alpha 1-acid glycoprotein and albumin, we found that alpha 1-acid glycoprotein causes the PS/TCA method to underestimate the total urine protein concentration, whereas the benzethonium chloride method is unaffected. Not all urinary albumin was precipitated by TCA when alpha 1-acid glycoprotein was present. Therefore, protein methods in which trichloroacetic acid is used as a concentrating step before the assay will underestimate total urine protein when the concentration of alpha 1-acid glycoprotein is high.

Topics: Azo Compounds; Benzethonium; Chemical Precipitation; False Negative Reactions; Humans; Immunoassay; Indicators and Reagents; Orosomucoid; Proteinuria; Trichloroacetic Acid

The purpose of this study was to detect the possibility of drug interference in the estimation of urine protein in patients receiving therapeutic doses of penicillin G, ampicillin, methicillin, cefoxitin, cefazolin, gentamicin, co-trimoxazole, phenothiazines, glibenclamide and acetazolamide. Five different methods for urine protein determination were compared in these patients, when different amounts of albumin were added to urine in vitro, and in a control group of patients not treated with drugs known to interfere with these methods. The techniques included two semi-quantitative tests--a strip test (Albustix) and heat and acetic acid turbidity test; and three quantitative tests--sulphosalicylic acid test, trichloroacetic acid test and a test based on a formation of Ponceau S dye-protein complex (Urin-Pak). The only significant interference found was that of gentamicin with the Ponceau S dye test.

Topics: Albumins; Anti-Bacterial Agents; Azo Compounds; Coloring Agents; Drug Interactions; False Positive Reactions; Gentamicins; Humans; Proteinuria

Six assays for protein in urine were compared for linearity, ease of standardization, precision, comparability of assay values, technical ease of assay, and current cost. The assays investigated were three dye-binding techniques, a recent turbidimetric technique, the trichloroacetic acid--biuret reaction, and a tannic acid protein precipitation reaction with ferric chloride. All assays suffered from standardization problems, although the biuret method showed the best analytical recovery of albumin and gamma-globulin. The tannic acid/ferric chloride method is dependent on sample pH. The turbidimetric assay exhibited the greatest imprecision; i.e., CVs were 19.5% at a protein concentration of 0.13 g/L and 6.0% at a protein concentration of 1.3 g/L. On the basis of all the factors assessed, we conclude that the Pesce/Strande Ponceau-S and the Bio-Rad Coomassie Brilliant Blue dye-binding techniques offer certain advantages over the other assays studied.

Topics: Azo Compounds; Biuret Reaction; Chlorides; Ferric Compounds; Humans; Hydrolyzable Tannins; Methods; Nephelometry and Turbidimetry; Proteinuria; Rosaniline Dyes; Trichloroacetic Acid