Beyond serology: using molecular methods for the detection of Rickettsia and Orientia in clinical samples.

Background: Serological assays and conventional PCR used for detecting Rickettsia and Orientia are time-consuming. Given that therapeutic approaches for these infections overlap, early molecular detection significantly enhances timely clinical management. This study evaluates the utility of real-time PCR for the detection of Rickettsia and Orientia compared with ELISA and the Weil-Felix test.

Methods: A total of 243 patients (92 females and 151 males) were enrolled. The Weil-Felix test and ELISA were performed to detect the spotted fever group, the typhus group and Orientia. Molecular testing included Pan-Rickettsial PCR targeting Pan antigen and real-time PCR for Orientia targeting 47 kDa. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy were calculated.

Results: Real-time PCR exhibited a sensitivity, specificity, PPV, NPV and accuracy of 88.5-95.0%, 83.25-96.0%, 81.91-96.0%, 89.42-95.0% and 85.68-95.0%, respectively. The ELISA showed a sensitivity, specificity, PPV, NPV and accuracy of 81.05-96.0%, 89.45-95.0%, 88-95.0%, 83.18-96.0% and 85.68-95.8%, respectively. The Weil-Felix test demonstrated a sensitivity, specificity, PPV, NPV and accuracy of 20.3-28%, 71-96.6%, 13-57%, 76.3-89% and 65-67%, respectively. Serological tests showed a positivity of 30-75% in convalescent-phase samples, whereas real-time PCR proved superior during the acute phase with a detection rate of 66.7-72.4%.

Conclusions: This study highlights the utility of real-time PCR as a rapid and effective tool for detecting Rickettsia and Orientia, reducing the turnaround time and simplifying the workflow.