Proteinuria is an important prognostic marker in the diagnosis and management of kidney diseases. Sulfosalicylic acid method (SSA) is a simple, low cost, qualitative test, widely used to assess proteinuria. The aim of this study was to optimize SSA test as a quantitative screening tool to assess proteinuria at lower excretory levels which would facilitate the screening and early diagnosis of renal impairment using protein-to-creatinine ratio (PCR). The study was conducted in two phases. In phase I, optimum SSA percentage to detect low-grade proteinuria was selected by comparing the performance of 3%, 6%, and 25% SSA methods in manual spectrophotometric analysis. In phase II, clinical applicability of the optimized method was evaluated using retained urine samples of patients with chronic kidney disease (CKD) assessed for urine protein by the pyrogallol red (PGR) method in a tertiary care hospital in Sri Lanka. Optimized 25% SSA protein-to-creatinine ratio (PCR) was compared with PGR PCR and albumin-to-creatinine ratio (ACR). Sensitivity, specificity, degree of agreement, correlation, and diagnostic accuracy were evaluated. Turbidimetric analysis using 25% SSA was linear in the range 3–50 mg/dL giving the highest analytical sensitivity. The test yielded a sensitivity of 86.5% and specificity of 96.5% and a degree of agreement of 5 mg/dL with the PGR method. Optimal cut-off for 25% SSA PCR in receiver operating characteristic analysis was 166 mg/g. Spearman’s correlation coefficient for 25% SSA PCR versus ACR was r = 0.823, , and for 25% SSA PCR versus PGR PCR was r = 0.913, . The 25% SSA PCR has a sensitivity of 92% against ACR, the current prognostic marker for proteinuria in patients with CKD. The 25% SSA test is a simple method, and it performs satisfactorily as a screening test with a cut-off for PCR optimized at 166 mg/g. The test merits further evaluation due to its low cost.

中文翻译：

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25％磺基水杨酸蛋白与肌酐比值的优化，用于筛选低度蛋白尿

蛋白尿是肾脏疾病诊断和治疗的重要预后指标。磺基水杨酸法（SSA）是一种简单，低成本的定性检测方法，广泛用于评估蛋白尿。这项研究的目的是优化SSA测试，作为定量筛查工具以评估较低排泄水平的蛋白尿，这将有助于使用蛋白与肌酐比值（PCR）筛查和早期诊断肾功能不全。该研究分两个阶段进行。在阶段I中，通过比较手动分光光度法分析中3％，6％和25％SSA方法的性能，选择了检测低度蛋白尿的最佳SSA百分比。在第二阶段 在斯里兰卡的一家三级医院中，通过使用邻苯三酚红（PGR）方法评估了慢性肾病（CKD）患者尿液蛋白含量进行了尿蛋白评估，评估了优化方法的临床适用性。将优化的25％SSA蛋白与肌酐之比（PCR）与PGR PCR和白蛋白与肌酐之比（ACR）进行比较。敏感性，特异性，一致程度，相关性和诊断准确性进行了评估。使用25％SSA进行的浊度分析在3–50 mg / dL范围内是线性的，具有最高的分析灵敏度。该测试使用PGR方法测得的灵敏度为86.5％，特异性为96.5％，一致度为5 mg / dL。接收器工作特性分析中25％SSA PCR的最佳截止值为166 mg / g。25％SSA PCR与ACR的Spearman相关系数为 将优化的25％SSA蛋白与肌酐之比（PCR）与PGR PCR和白蛋白与肌酐之比（ACR）进行比较。敏感性，特异性，一致程度，相关性和诊断准确性进行了评估。使用25％SSA进行的浊度分析在3–50 mg / dL范围内是线性的，具有最高的分析灵敏度。该测试使用PGR方法测得的灵敏度为86.5％，特异性为96.5％，一致度为5 mg / dL。接收器工作特性分析中25％SSA PCR的最佳截止值为166 mg / g。25％SSA PCR与ACR的Spearman相关系数为 将优化的25％SSA蛋白与肌酐之比（PCR）与PGR PCR和白蛋白与肌酐之比（ACR）进行比较。敏感性，特异性，一致程度，相关性和诊断准确性进行了评估。使用25％SSA进行的浊度分析在3–50 mg / dL范围内是线性的，具有最高的分析灵敏度。该测试使用PGR方法测得的灵敏度为86.5％，特异性为96.5％，一致度为5 mg / dL。接收器工作特性分析中25％SSA PCR的最佳截止值为166 mg / g。25％SSA PCR与ACR的Spearman相关系数为 使用25％SSA进行的浊度分析在3–50 mg / dL范围内是线性的，具有最高的分析灵敏度。该测试使用PGR方法测得的灵敏度为86.5％，特异性为96.5％，一致度为5 mg / dL。接收器工作特性分析中25％SSA PCR的最佳截止值为166 mg / g。25％SSA PCR与ACR的Spearman相关系数为 使用25％SSA进行的浊度分析在3–50 mg / dL范围内是线性的，具有最高的分析灵敏度。该测试使用PGR方法测得的灵敏度为86.5％，特异性为96.5％，一致度为5 mg / dL。接收器工作特性分析中25％SSA PCR的最佳截止值为166 mg / g。25％SSA PCR与ACR的Spearman相关系数为r  = 0.823，，对于25％的SSA PCR和PGR PCR， r  = 0.913，。25％的SSA PCR对ACR的敏感性为92％，ACR是CKD患者目前蛋白尿的预后指标。25％SSA测试是一种简单的方法，它可以令人满意地作为筛选测试，具有针对166 mg / g优化的PCR的临界值。由于成本低，该测试值得进一步评估。