Nickan Research Institute Immunopathologia Persa 2423-8015 12 2 2026 07 01 The diagnostic value of spot urine protein‑to‑creatinine ratio in the diagnosis of proteinuria severity; a diagnostic cross-sectional study e44023 e44023 10.34172/ipp.2026.44023 EN Sepideh Hajian https://orcid.org/0000-0002-3368-0036 Negar Sheikhdavoodi https://orcid.org/0000-0003-1686-4893 Arian Ghannadi Karimi https://orcid.org/0000-0002-5241-4905 Mehran Ebrahimi Varkiani https://orcid.org/0009-0004-2421-1029 Pourya Ebizadeh Tourabifard https://orcid.org/0009-0004-3115-6101 Fatemeh Ghasemi Ghale Bahmani https://orcid.org/0009-0000-3978-1180 Darya Ipchian https://orcid.org/0009-0008-8730-0597 Journal Article 10.34172/ipp.2026.44023 2025 12 05 2026 05 06 Introduction: Proteinuria is a key marker of renal dysfunction, yet its accurate quantification traditionally relies on 24‑hour urine collection, a method that is time‑consuming and often impractical in routine clinical settings. The spot urine protein‑to‑creatinine ratio (P/CrR) has emerged as a potential alternative, offering a simpler and more accessible approach for assessing protein excretion. Objectives: This study aimed to evaluate the diagnostic value of spot urine P/CrR in identifying and stratifying the severity of proteinuria. Materials and Methods: This diagnostic cross‑sectional study enrolled 87 individuals with confirmed proteinuria who were referred to the outpatient clinics or inpatient wards of Qazvin hospitals between March and August 2020. Following informed written consent, spot urine samples and 24‑hour urine collections were obtained under sterile laboratory conditions. The diagnostic utility of the spot urine P/CrR for identifying and stratifying proteinuria severity was evaluated in comparison with the 24‑hour urine protein measurement as the reference standard. Results: The study demonstrated that the spot urine P/CrR was strongly associated with proteinuria severity. Logistic regression showed that each unit increase in P/CrR increased the odds of moderate proteinuria, with unadjusted and adjusted odds ratios (ORs) of 1.05 and 1.06, respectively, and similarly increased the odds of severe proteinuria, with corresponding OR of 1.07 and 1.08. Diagnostic analysis indicated that a spot P/CrR threshold of 200 mg/g provided good discriminatory performance, yielding a sensitivity and specificity of 81% and 74% for moderate proteinuria and 91% and 74% for severe proteinuria. Conclusion: Spot urine P/CrR showed a strong and graded association with proteinuria severity, with meaningful increases in odds across both moderate and severe categories and good diagnostic performance at the 200 mg/g threshold. These findings support its value as a simple and reliable marker for identifying and stratifying proteinuria severity.