Diagnostic Accuracy of the Proteinuria-to-Creatinineuria Ratio in Thrombotic Thrombocytopenic Purpura

Abstract

Background: Thrombotic Thrombocytopenic Purpura (TTP) is a life-threatening thrombotic microangiopathy requiring rapid diagnosis and treatment. Although ADAMTS13 activity testing is the gold standard for diagnosis, it remains largely inaccessible in low-resource settings, necessitating alternative, cost-effective diagnostic markers. The proteinuria-to-creatinineuria (PU/CU) ratio has been suggested as a potential noninvasive surrogate for early TTP detection. Objective: This study aimed to evaluate the diagnostic accuracy of the PU/CU ratio (>1.5 g/g) for identifying TTP using ADAMTS13 activity (<10%) as the gold standard, and to assess its performance across different clinical subgroups. Methods: A cross-sectional validation study was conducted at Mayo Hospital, Lahore, with 290 patients aged 16–75 years presenting with clinical features of thrombotic microangiopathy. Patients with renal failure, liver disease, malignancy, HIV, or pregnancy-related TMAs were excluded. Blood and urine samples were analyzed for ADAMTS13 activity and PU/CU levels, respectively. Ethical approval was obtained, and informed consent was secured in compliance with the Helsinki Declaration. Data were analyzed using SPSS v27, with sensitivity, specificity, predictive values, and accuracy computed from 2×2 contingency tables. Results: The PU/CU ratio demonstrated a sensitivity of 83.3%, specificity of 78.4%, PPV of 85.3%, NPV of 75.8%, and diagnostic accuracy of 81.4% in detecting TTP. These findings remained consistent across stratified subgroups. Conclusion: The PU/CU ratio is a reliable and practical screening tool for early TTP diagnosis, particularly in settings lacking access to ADAMTS13 testing. Its integration into clinical protocols may improve early recognition and timely intervention.