The purpose of this study was to evaluate the diagnostic accuracy of fast antigen and antibody kits in relation to the Widal test for both early detection (<5 days of fever) and late detection (>5 days of fever) of S.Typhi and S.Paratyphi. Over the course of 15 months, 180 patients with confirmed fever cases were enrolled in a cross-sectional observational study. The rapid antigen test (RAg), rapid antibody test (RAb), and Widal test were performed on paired samples taken (at <5 and >5 days of fever). The gold standard for verification was a blood culture (using the BacT/Alert system). Patients with enteric fever had a mean (SD) age of 16.42 (12.53) years, with men somewhat outnumbering women (58.33% vs. 41.67%). The blood cultures of 58 patients (32.22%) were positive. The diagnostic accuracy of the RAg, RAb, and Widal tests for enteric fever in cases with less than 5 days of fever was 45.56%, 42.22%, and 41.11%, respectively, which was comparable (P=0.675). When comparing RAg’s diagnostic accuracy to that of RAb (61.11%) and the Widal test (66.11%) for fever lasting more than 5 days, RAg performed significantly worse at 15% (P<0.0001). The study results indicate that RAg has a high sensitivity for making a correct diagnosis within the first five days of typhoid fever, while RAb (with or without Widal tests) has a higher sensitivity for making a diagnosis after 5 days of enteric fever.

Source: journals.lww.com/jfmpc/Fulltext/2022/07000/Comparison_of_rapid_tests__antigen_vs__antibody_.54.aspx