Urinary albumin strip assay as a screening test to replace quantitative technology in certain conditions

Background The clinical laboratory plays a crucial role in the diagnosis and monitoring of chronic kidney disease. The quantitative measurement of urine albumin in a spot sample, expressed as ratio per creatinine (ACR) is the most frequently used biomarker for such a purpose. Our aim was to evaluate the diagnostic performances of a strip for measuring ACR for differentiating patients who are candidates for subsequent albumin quantification, and to evaluate the economic effects of its implementation. Methods We systematically measured strip analysis when quantitative urinary albumin was requested. Semiquantitative urinary albumin was measured using a UC-3500 (Sysmex, Kobe, Japan), based on the protein error of a pH indicator. We collected and reviewed all the values of quantified urinary albumin and their corresponding results in ACR strip tests. We calculated the diagnostic indicators for ACR at different albumin and creatinine values using the quantitative ACR measurement as a "gold standard". We also studied the economic effects based on both tests prices (€1.31 for quantitative albumin plus creatinine, and €0.04 for an albumin strip). Results The study included 9148 patients (mean age 63, 46.3% men). The results at different albumin and creatinine cutoffs showed the best performance when 10 mg/L and above 50 mg/dL, respectively. Based on our results, we would have saved 3506 urine albumin and creatinine tests in the study period, corresponding to €4226.94. Conclusions The present study supports the use of the ACR strip test to identify pathological albuminuria values to be measured through quantitative methods. Considerable economic savings are possible.