Assessment of Rapid Diagnostic Tests for Typhoid Diagnosis and Assessment of Febrile Illness Outbreaks in Fiji

Abstract

Typhoid is an endemic in Fiji with increases observed since the early 2000s and frequent outbreaks reported. We assessed the diagnostic accuracy of currently available typhoid rapid diagnostic tests (RDTs) (TUBEX, Typhidot Rapid, and Test-It assay) to establish their performance against blood culture in Fiji and to examine their suitability for rapid typhoid outbreak identification. The performance of RDTs was assessed in the public health reference laboratory in Suva, Fiji, according to the manufacturers’ instructions. A simulation was used to examine the potential use of RDTs for attribution of a febrile illness outbreak to typhoid. For the diagnostic evaluation, 179 patients were included; 49 had blood culture–confirmed typhoid, 76 had fever as a result of non-typhoid etiologies, and 54 were age-matched community controls. The median (interquartile range) age was 29 (20–46) years. Of the participants, 92 (51.4%) were male and 131 (73.2%) were indigenous Fijians. The sensitivities of the tests were 77.6% for TUBEX, 75.5% for Typhidot Rapid, and 57.1% for Test-It assay. The Test-It assay had the highest specificity of 93.4%, followed by Typhidot Rapid 85.5% and TUBEX 60.5%. Typhidot Rapid had the best performance in the simulation for attribution of a febrile illness outbreak to typhoid. Typhoid RDTs performed suboptimally for individual patient diagnosis due to low sensitivity and variable specificity. We demonstrate that RDTs could be useful in the field for rapid attribution of febrile illness outbreaks to typhoid. Typhidot Rapid had the best combination of sensitivity, specificity, positive and negative predictive values, cost, and ease of use for this purpose.

Comparative Analysis of Commercially Available Typhoid Point-of-Care Tests: Results of a Prospective and Hybrid Retrospective Multicenter Diagnostic Accuracy Study in Kenya and Pakistan

“…In general, the findings of this study are supported by those of previous studies ( 16 – 24 ). A study in Bangladesh reported similar findings for the SD Bioline S .…”

“…Typhi IgG/IgM Fast, the Typhoid IgG/IgM Combo Rapid Test CE (IgM component) and Test-it Typhoid IgM ( 16 ). The specificity findings for the Typhidot Rapid IgG/IgM Combo test are also consistent with a recent study conducted in Fiji, as are the Test-it Typhoid IgM findings ( 17 ). The sensitivity and/or specificity results for the TUBEX TF test were consistent with those reported in studies conducted in various regions, including Bangladesh, Southern Vietnam and Papua New Guinea, as well as a systematic review and meta-analysis of studies in several countries where typhoid is endemic ( 9 , 18 , 19 , 21 ).…”

“…However, there are also studies for many of the RDTs that show slightly to widely contrasting sensitivity and specificity values ( 16 – 18 , 25 – 28 ), probably due to smaller sample sizes and reference standard differences. Nevertheless, considering the head-to-head nature of this study and the consistent methodology/reference standards employed, together with the broad consensus of the findings across the literature, the results presented here may help the WHO and health provider decision-making regarding the utility of commercial RDTs in different settings and use cases, while clearly highlighting which tests should not be used in practice.…”

Comparative Analysis of Commercially Available Typhoid Point of Care Tests: Results of a Prospective and Hybrid Retrospective Multicenter Diagnostic Accuracy Study in Kenya and Pakistan

“…Typhi IgG/IgM Fast, the Typhoid IgG/IgM Combo Rapid Test CE (IgM component) and Test-it™ Typhoid IgM (15). Specificity findings for the Typhidot Rapid IgG/IgM combo test are also consistent with a recent study conducted in Fiji, as are the Test-it™ Typhoid IgM findings (16). Sensitivity and/or specificity results for the TUBEX TF test were consistent with those reported in studies conducted in various regions, including Bangladesh, Southern Vietnam and Papua New Guenea as well as a systematic review and meta-analysis of studies in several typhoid-endemic countries (9, 17, 18, 20).…”

False sero-positivity of Salmonella typhi Specific Antibody in Dengue and Corona Virus Infected Patients: An Observational Study

“…A false diagnosis of enteric fever through Widal agglutination test may result in the unnecessary use of antimicrobial drugs and provoke the development of drug-resistant bacteria. [17][18][19] Based on our finding we can conclude that, false positivity in the serological test should be interpreted carefully and base line titre should be monitored frequently to overcome the misdiagnosis. There should be a continuous follow up of the patients and more accurate diagnostic test should be performed to rule out the false positivity.…”