ORCID Profile
0000-0002-2316-1929
Current Organisation
Università degli Studi di Milano
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Publisher: Wiley
Date: 22-08-2018
DOI: 10.1111/VCP.12646
Abstract: Proteinuria quantification with the urinary protein-to-creatinine (UPC) ratio is part of the diagnostic process in feline patients suspected of chronic kidney disease (CKD). In affected cats, monitoring and substaging of the UPC according to the International Renal Interest Society (IRIS) guidelines is also necessary for appropriate patient management. No information is available about the possible effects of analytical variability on urinary proteins (UPs) and the UPC ratio in cats. This study aimed to determine whether imprecision and method-dependent differences due to the two dye-binding methods, pyrogallol red-molybdate (PRM) and Coomassie brilliant blue (CBB), could affect IRIS substaging. Urine s les were collected from proteinuric and nonproteinuric cats. Intra-assay and inter-assay repeatability were assessed with both the PRM and CBB methods. Urinary supernatants (n = 120) were tested using both methods. Agreement between the methods and concordance with s le classification according to IRIS guidelines were determined. On average, the PRM method yielded a higher CV (UP 8.4 ± 5.2% UPC 9.5 ± 4.8%) than the CBB method (UP 5.6 ± 2.6% UPC 7.2 ± 2.6%), but similar rates of misclassification were found in s les with UPC ratios close to the IRIS cut-off. Although the two methods were correlated, the CBB method tended to yield UPs and UPC ratios that were significantly higher (P < 0.0001) than that of the PRM method. The Passing-Bablok test also found constant and proportional errors between the PRM and CBB methods. Concordance in substaging s les according to IRIS was good (k coefficient = 0.62). The two methods were precise, but the higher UPC ratios obtained with the CBB methods might affect the interpretation using the IRIS guidelines and clinical decisions.
Publisher: Wiley
Date: 28-07-2021
DOI: 10.1111/VCP.12994
Abstract: To date, little information is available about the effect of preanalytical factors on the urinary protein‐to‐creatinine (UPC) ratio in cats. We aimed to evaluate the effect of a commercially available cat litter, creatinine measurements at three different dilutions of urine, and different storage conditions on the UPC ratio in cats. Feline urine specimens were prospectively collected. Twenty‐two whole‐urine specimens were placed uncovered and in contact with cat litter for 1 hour 25 urine supernatants were diluted 1:10, 1:20, and 1:100 for creatinine measurements. The correlation, difference, agreement, and concordance in classifying specimens according to International Renal Interest Society staging were determined. Storage effects on UPC ratios were assessed in specimens stored for 6 hours at +20℃ (n = 20), 1 week at +4℃ (n = 20), and 3 months at −20℃ (n = 25). Specimens were also subjected to four freeze‐thaw cycles (n = 20). Results were compared, and clinical significance was assessed by comparing each UPC ratio to the inter‐assay range of the baseline value. Exposure to cat litter did not affect UPC ratios. A positive proportional bias was found in the 1:100 dilution compared with the 1:20 dilution however, concordance was high for all comparisons. At +20, +4℃, and after four repeated freeze‐thaw cycles, UPC ratios were stable. Compared with baseline values, UPC ratios decreased ( P .01) after 8 and 12 weeks at −20℃. However, all UPC ratios were within the inter‐assay variability of the baseline value. Exposure to cat litter did not affect UPC ratios, but further studies are necessary to evaluate other potential variables. The effects of the dilutions and storage conditions were clinically acceptable, although the 1:20 and 1:100 dilutions were not perfectly comparable.
Publisher: Elsevier BV
Date: 04-2015
DOI: 10.1016/J.TVJL.2015.01.029
Abstract: Quantification of proteinuria is a fundamental step in staging dogs with chronic kidney disease and in monitoring the course of disease or the efficacy of anti-proteinuric treatments. Analytical precision and accuracy of the proteinuria assessment could be affected by several factors such as biological variability, different operators and quality control materials. The aim of this study was to assess whether inter-laboratory variability could affect the urinary protein to creatinine (UPC) ratio and whether this variability may affect patient classification according to the International Renal Interest Society (IRIS) sub-staging system. The same urine s les were analysed in three different laboratories using different instruments and different reagent brands. The results of the three laboratories were highly correlated to each other although urinary protein (UP), urinary creatinine (UC) and the UPC ratio of one laboratory were found to be significantly higher than those of the other two. No significant differences between the other two laboratories were recorded. The concordance in classifying dogs according to the IRIS guidelines was good if all three proteinuria categories were analysed separately or if borderline proteinuric (BP) dogs were included in the proteinuric group, and very good if BP dogs were merged into the non-proteinuric group. The inter-laboratory variability in UPC ratio measurement was not so great as to impede the identification of proteinuric dogs, but may influence the estimation of the magnitude of proteinuria.
Publisher: Wiley
Date: 26-08-2016
DOI: 10.1111/VCP.12388
Abstract: Urinary protein-to-creatinine (UPC) ratio is an early diagnostic and prognostic marker of renal disease in dogs. Pyrogallol red molybdate (PRM) and Coomassie brilliant blue (CBB) are the most popular dye-binding assays for measurement of proteinuria. Published guidelines recommend strict cut-off points to substage patients with chronic renal diseases, irrespective of the assay applied. However, analytic variability and method-dependent differences could affect substaging of patients. The aims of this study were to analytically validate the CBB assay to evaluate possible method-dependent differences with PRM in urinary protein (UP) determination, and to assess the influence of such differences in substaging according to the International Renal Interest Society (IRIS). Urine was collected from healthy and proteinuric dogs. Intra-assay and inter-assay repeatability (imprecision), linearity under dilution (LUD), and spiking recovery (inaccuracy) were determined for the CBB assay. Split s les were measured with PRM and CBB, and agreement between methods and concordance in classification according to IRIS guidelines was determined. The CBB assay was precise (< 10%) at all urine protein concentrations after excluding outliers from the intra-assay precision assay of high urine protein concentrations. Acceptable accuracy was demonstrated with both LUD and spiking recovery test. Both UP and UPC determined by CBB were significantly higher (P < .0001) than those obtained with PRM, and both a constant and proportional bias were present. Concordance of IRIS substaging was only moderate. The CBB is precise and accurate, but the higher UPC obtained with CBB vs PRM may affect interpretation of the IRIS guidelines.
No related grants have been discovered for Paola Scarpa.