High False-Positive Rate of Syphilis Serological Screening in Male Blood Donors: A Molecular Validation Study

<ns7:p>Background Accurate serological screening is fundamental to transfusion safety. The VDRL test remains extensively used for syphilis screening despite documented limitations in sensitivity and specificity. Objectives This study validated VDRL results through PCR, determined true Treponema pallidum prevalence among VDRL-positive blood donors, established diagnostic accuracy of ELISA and rapid tests, and enhanced blood safety protocols. Materials and Methods A cross-sectional diagnostic accuracy study was conducted at the Al-Ramadi regional blood transfusion facility between February and August 2024. Among 5,579 male blood donors aged 18-65 years who underwent screening, 50 demonstrated VDRL reactivity (0.90%). Confirmatory testing protocols included treponemal-specific ELISA, rapid immunochromatographic assays, and real-time PCR targeting the *T. pallidum polA* gene. Diagnostic performance parameters were calculated using PCR (reported sensitivity 99%, specificity 98%) as the reference standard. Results VDRL reactivity was detected in 0.90% (50/5,579) of male blood donors. All VDRL-reactive specimens demonstrated concordant positive results on both ELISA and rapid immunochromatographic platforms. However, PCR analysis detected *T. pallidum* DNA in only 29 specimens (58%), revealing that 21 specimens (42%) represented false-positive serological reactions. Diagnostic accuracy analysis comparing serological assays against PCR demonstrated limited discriminatory performance: ELISA exhibited 100% concordance with VDRL among reactive specimens but failed to distinguish true infections from false-positive reactions (positive predictive value 58%). The rapid diagnostic test demonstrated comparable limitations. High VDRL titers (≥1:8) demonstrated strong correlation with PCR positivity (87.5%), whereas low titers (1:1-1:4) exhibited poor correlation (41.0%). False-positive rates were highest among donors aged 35-44 years. The disposal of blood units based on false-positive serological results represents substantial wastage of valuable blood resources. Conclusion Molecular confirmation of reactive specimens enhances transfusion safety and conserves blood resources. The high false-positive rate (42%) necessitates urgent revision of screening algorithms and implementation of PCR confirmation strategies.</ns7:p>