Introduction: Acute kidney injury (AKI) is a common and high-risk complication of COVID-19. Serum creatinine rises with delay, which limits early recognition of renal involvement (7,9). Inflammatory and coagulation biomarkers measured at hospital admission may provide an earlier indication of AKI (1,4,10–12).
Materials and Methods: We analysed 436 hospitalisations with PCR-confirmed COVID-19 (01.2021–12.2022) at St. Marina University Hospital, Varna. AKI was defined according to KDIGO 2012 (by serum creatinine; the urine-output criterion was unavailable) (7). First-hour measurements included CRP, D-dimer, fibrinogen, ferritin, and LDH. ROC curves and Youden’s J were used to determine optimal cut-offs; an additional combined model was constructed from the three markers (CRP > 150 mg/L; D-dimer > 0.75 mg/L; fibrinogen > 6 g/L). Multivariable logistic regression was adjusted for age, sex, arterial hypertension, and diabetes (6,8,14).
Results: 94/436 (21.6%) developed AKI. At admission, CRP, D-dimer, and fibrinogen were higher in patients who subsequently developed AKI; ferritin and LDH showed trends without independent predictive value. Individual AUCs: CRP 0.69, D-dimer 0.74, fibrinogen 0.62; the combined model achieved AUC 0.82. At the chosen threshold, sensitivity was 72% and specificity 76%. In the multivariable model, D-dimer > 0.75 mg/L (OR 2.3; 95% CI 1.4–3.8), CRP > 150 mg/L (OR 1.9; 95% CI 1.2–3.0), fibrinogen > 6 g/L (OR 1.6; 95% CI 1.1–2.6), and age > 70 years (OR 1.7; 95% CI 1.1–2.8) were independent predictors. A negative result on the combined assessment virtually rules out AKI (residual risk ≈ 9%), whereas a positive result indicates that nearly one in two patients will develop this complication (≈ 45%).
Conclusion: A triad of CRP, D-dimer, and fibrinogen available within the first hour of admission provides early and inexpensive risk stratification for COVID-19-associated AKI, consistent with published evidence on the roles of inflammation and coagulopathy (1,4,10–13). Its implementation may support nephroprotective strategies and prioritisation for early consultation (9,10).
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