Limitations of typhoid fever diagnostics and the need for prevention.

Evaluation of: Siba V, Horwood PF, Vanuga K et al. Evaluation of serological diagnostic tests for typhoid fever in Papua New Guinea using a composite reference standard. Clin. Vaccine Immunol. 19(11), 1833-1837 (2012). The study under review evaluated serological tests for typhoid fever against PCR as a reference test. While laboratory testing is essential for the confirmation of this severe disease, the low bacterial load and the low level of specific antibodies in the blood of typhoid patients combined with its acute character make interpretation of laboratory testing cumbersome. Validation of an index test requires good understanding of the diagnostic performance and assay characteristics of the reference test, and criteria and principles for study design and reporting outlined by the Quality Assessment of Diagnostic Accuracy Studies and the Standards for Reporting Studies of Diagnostic Accuracy should be followed. Described PCR assays for typhoid fever have not been validated against bone marrow culture, the gold standard, and their diagnostic utility remains to be established.