28Misdiagnosis of enteric fever is a major global health problem resulting in patient mismanagement, 29 antimicrobial misuse and inaccurate disease burden estimates. Applying a machine-learning algorithm 30 to host gene expression profiles, we identified a diagnostic signature which could accurately 31 distinguish culture-confirmed enteric fever cases from other febrile illnesses (AUROC>95%). 32Applying this signature to a culture-negative suspected enteric fever cohort in Nepal identified a 33 further 12.6% as likely true cases. Our analysis highlights the power of data-driven approaches to 34 identify host-response patterns for the diagnosis of febrile illnesses. Expression signatures were 35 validated using qPCR highlighting their utility as PCR-based diagnostic for use in endemic settings. 36. CC-BY-NC-ND 4.0 International license It is made available under a (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/327429 doi: bioRxiv preprint first posted online May. 21, 2018; 3 Enteric fever, a disease caused by systemic infection with S. enterica serovars Typhi or Paratyphi A, 37 accounts for 13.5 to 26.9 million illness episodes worldwide each year.1,2 In resource-limited tropical 38 settings these infections are endemic and the accurate diagnosis of patients presenting with 39 undifferentiated fever is challenging. 40Diagnostic tests for enteric fever rely on microbiological culture or detection of a serological response 41 to infection, and are often unavailable or insufficiently sensitive and specific.3 Blood culture remains 42 the reference standard against which new diagnostic tests are evaluated, and the sensitivity for this test 43 can reach 80% under optimal conditions 4 but low blood volumes and uncontrolled antibiotic use often 44 result in decreased sensitive in the field. New diagnostic approaches are urgently needed to enable the 45 accurate detection of enteric fever cases in endemic settings, to guide management of febrile patients, 46 appropriate use of antimicrobials, and to identify populations likely to benefit from vaccine 47
implementation. 48Most common tests used for acute infectious disease diagnosis employ methods to directly detect the 49 disease-causing pathogen, either by culture, antigen detection or amplification of genetic material by 50PCR. An alternative approach is to identify a set of human host immune responses, which together 51 may generate a specific pattern associated with individual infections or pathogens. With an increasing 52 quantity of molecular host response data being generated by high-throughput methods -including 53 whole blood gene expression profiling -differences in the activation status of the immune response 54 network during infection may be a tractable diagnostic approach. Recently small sets containing 2-3 55 genes have been described, the expression of which can accurately differentiate between viral or...