Different causes of acute febrile illness due to different infectious diseases (e.g. bacterial, viral malaria) may present with a similar clinical presentation. We performed a clinical diagnostic study to assess the diagnostic accuracy of a new tool - the Infection Manager System (IMS) - an algorithm which uses haemocytometric data to predict the cause of infection (e.g. bacterial, viral, malaria). The current dataset is a subset of data obtained during this study which was performed in a rural setting in Burkina Faso. The study was registered at ClinicalTrials.org under Identifier NCT02669823. All data used for the manuscript entitled "Infection Manager System (IMS) as a new hemocytometry-based bacteremia detection tool: a diagnostic accuracy study in a malaria-endemic area of Burkina Faso" are included in the current subset of data.

To test the IMS we collected clinical and demographic data from approximately 900 patients aged between 3 months and 100 years presenting with an acute febrile illness. Upon inclusion, 2-5 ml EDTA anticoagulated blood was sampled for haemocytometry, malaria diagnostics (thick- and thin blood films and RDTs) and blood culture. A nasopharyngeal swab and aliquots of residual blood and plasma were stored at -80° for retrospective analyses. 1. A viral panel on nasopharyngeal swabs 2. PCR's for malaria, Salmonella, S. aureus, H. influenzae, S. pneumoniae on whole blood or plasma samples and 3. C-reactive protein (CRP) and procalcitonin (PCT) levels on plasma samples. Additional diagnostics such as chest X-ray, echography, urinalysis, and culture of urine, stool, pus, or cerebrospinal fluid were performed on clinical indication.

In this cohort we attempted to provide a microbiologically proven diagnosis for all patients admitted with febrile illness using gold standard methods (e.g. blood culture, malaria microscopy and PCR). We then assessed the accuracy of the novel IMS to differentiate causes of infection against these conventional diagnostic methods. We furthermore assessed the accuracy of both CRP and PCT in differentiating causes of infection and compared them to the performance of the IMS.

We found that the IMS had a higher diagnostic accuracy to detect bacteremia than PCT at a cut of value of 0.5 µg/L, and was comparable in sensitivity, but superior in specificity to CRP at a cut of value of 20 mg/L. Subanalysis among patients below the age of five showed that they had a slightly lower accuracy of IMS, PCT and CRP. Combining the IMS and CRP did not significantly improve accuracy due to the high level of overlap between CRP and the IMS. The high negative predictive value of IMS –also in non-bacteremic bacterial infections – suggests that the IMS holds promise to rationalize antimicrobial prescription in healthcare facilities where hematology analyzers are available. The relatively low specificity and PPV demonstrate that it is not (yet) suitable as a diagnostic for bacteremia.