Performance of TUBEX® TF IgM Antibody Test Against Culture to Detect Typhoid Fever Among Hospitalized Patients in Nairobi County

Typhoid fever has remained endemic and a major health problem in developing countries like Kenya due to poor sanitation, overcrowding and limited access to diagnostic services. The main aim of this study was to determine the diagnostic value of TUBEX ® TF IGM antibody tests for early diagnosis of typhoid fever among hospitalized patients in Nairobi County. TUBEX ® TF is a competitive immunoassay which detects presence of anti-09 IgM Salmonella Typhi antibodies in a patient’s serum. We studied TUBEX ® TF a rapid sera diagnostic test for its usefulness in early diagnosis of typhoid fever and we compared its sensitivity and specificity to that of Widal test. The study was conducted on 92 (Gp-I) febrile patients who had clinically suggestive signs and symptoms of typhoid fever. Two groups of controls were created; 45 (Gp-II) and 15 (Gp-III) age and sex matched febrile and healthy controls, respectively.  Blood culture was performed in all cases while TUBEX ® TF and Widal tests were performed in both cases and controls. The sample size was based on convenience at the two health facilities of our study. Gp-I had 9 (9.78%) blood culture positives for S. Typhi, 11(11.99%) were positive for TUBEX ® TF while 17 (18.48%) were positive for Widal test. 3 (6.67%) Gp-II were positive on both TUBEX ® TF and Widal test while none of the two tests tested positive on Gp-III. Among 9 culture positive cases, TUBEX ® TF was positive in 8 cases same as Widal test with sensitivity, specificity, PPV and NPV values of 88.9% (95% CI: 51.18-99.7), 97.6% (95% CI: 91.6-99.7), 80.0 %(95% CI: 44.4-97.5), 98.8 %(95% CI: 93.4-100), respectively. Widal test had 88.89% (95% CI: 51.8-99.7), 90.4% (95% CI: 81.9-95.7), 50.00% (95% CI: 24.7-75.3), 98.7% (95% CI: 92.9-100) respectively. This study demonstrated better results with TUBEX ® TF test compared to Widal test when blood culture was used as a gold standard. However, these results should be further confirmed by using multiple gold standard tests such as molecular and enzyme-linked immunosorbent assays and carried out on large scale cross-sectional studies with varied prevalence of typhoid fever in the population. Keywords : Typhoid fever, TUBEX ® TF, Widal, Cases and Controls. DOI : 10.7176/JBAH/9-4-08