Beyond thrombocytopenia: clinical predictors of PCR-confirmed Crimean-Congo hemorrhagic fever in Thi-Qar, Iraq (2023–2024)

Abstract Background Crimean-Congo hemorrhagic fever (CCHF) is a major public health challenge in endemic areas with a wide spectrum of clinical manifestations that may overlap with other acute febrile illnesses. Identifying clinical predictors associated with laboratory-confirmed infection may support the early assessment and prioritisation of suspected cases. Objective To identify independent clinical predictors of PCR-confirmed CCHF among suspected cases reported in Thi-Qar governorate, southern Iraq, and to evaluate a simple clinical score based on these predictors. Methods A retrospective, surveillance-based study was conducted using records of suspected CCHF cases from January 2023 to December 2024. We used PCR results to classify cases as confirmed or non-confirmed. We used univariate and multivariable logistic regression to assess factors independently associated with PCR-confirmed infection. A three-point score based on fever, thrombocytopenia, and injection site bleeding was evaluated using receiver operating characteristic analysis and screening performance measures. Results Of 806 suspected patients, 190 tested PCR-positive. In the multivariable analysis, fever (AOR = 13.70, 95% CI: 3.25–58.82, P < 0.001), thrombocytopenia (AOR = 9.26, 95% CI: 3.61–23.81, P < 0.001), injection-site bleeding (AOR = 1.85, 95% CI: 1.05–3.25, P = 0.002), urban residence (AOR = 1.906, 95% CI:1.272–2.857, p = 0.002), and epidemiological exposure (AOR = 8.13, 95% CI: 5.15–12.66, p < 0.001) were independently associated with PCR-confirmed CCHF. By comparison, subcutaneous bleeding did not remain statistically significant after adjustment for other variables. A three-point clinical score, assigning 1 point each for fever, thrombocytopenia, and injection-site bleeding, showed a significant increase in PCR positivity ( p < 0.001) with increasing score from 0% at score 0 to 41.5% at score 3. The score showed modest discriminatory performance (AUC = 0.643, 95% CI: 0.601–0.684, p < 0.001); at a cut-off of ≥ 2, sensitivity was 98.4%, specificity was 24.2%, and negative predictive value was 98.0%. Conclusion Fever, thrombocytopenia and injection-site bleeding were independently associated with PCR-confirmed CCHF among suspected cases in Thi-Qar, Iraq. The proposed three-point score may support early screening and prioritisation when considered alongside epidemiological exposure. However, its modest discrimination and low specificity suggest the score is exploratory and requires further internal and external validation before routine clinical use.