A Rapid Triage Test to Improve Risk-stratification of Febrile Children (EChiLiBRiST, Clinical Trial 1, Outpatients)

The overall aim of the study is to provide evidence that introducing soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) evaluation at triaging (first clinical assessment), in combination with IMCI-based guidelines (SoC), is a viable strategy to enhance rapid and accurate identification of febrile children at increased risk of life-threatening infections compared to IMCI-based strategies alone (SoC), and to demonstrate whether this results in enhanced decisions of admission/referral vs discharge, and enhanced overall health outcome of children with acute fever in sub-Saharan Africa.

This is a multi-country, open label, two-arm, parallel-group, superiority, individually randomised clinical trial involving 2,606 febrile children per country (two countries, total n=5212). The trial will compare the performance of a point-of-care rapid triage test (POC-RTT) based on sTREM-1 levels (i.e. B-Triage) (in combination with IMCI-based strategies, which are the SoC) to appropriately support admission/referral vs discharge decisions during the first clinical assessment of febrile children aged 2-\<60 months compared to the standard of care based on IMCI guidelines.

Febrile children meeting the study eligibility criteria will be randomly allocated (1:1) to one of the two triaging approaches (arms): 1) IMCI-based standard of care (SoC); or 2) IMCI-enhanced by sTREM-1 levels (SoC + sTREM-1 POC). Blood will be collected from all participants and only those randomised to the intervention arm (arm 2) will have sTREM-1 levels determined at the POC using B-Triage device.

At baseline, all children will undergo two clinical assessments. Primary composite endpoint of "appropriateness of discharge" will be based on the first clinical assessment, which is more representative of real-world clinical practice. However, the ultimate decision on admission/referral vs discharge will be based on the second clinical assessment, which will ensure the safest possible clinical practice in the context of a clinical trial.

1. At baseline, during the first clinical assessment, all participants will be evaluated following the SoC based on IMCI guidelines, which will guide management decisions, including clinical diagnosis and treatment. This IMCI-guideline based evaluation during this first clinical assessment will be conducted by a health worker as per routine clinical practice in the outpatient departments of each study site.

   1. In the participants randomised to the control arm, decision of admission/referral vs discharge home will be informed by IMCI-based evaluation alone (SoC).
   2. In the participants randomised to the intervention arm, decision of admission/referral vs discharge home will be informed by IMCI-based evaluation enhanced by sTREM-1 levels (SoC + sTREM-1 POC). Clinicians will be instructed to admit for further observation any child with sTREM-1 levels equal or superior to 200 pg/mL, as these patients are at moderate or high risk of adverse outcomes and death. On the other hand, children with sTREM-1 levels below 200 pg/mL will be eligible for discharge home at the criteria of the clinician, considering the signs and symptoms found, and based on IMCI guidelines. Hence, should clinicians in charge deem that any of these children still require admission, they will be instructed to continue with the admission regardless of sTREM-1 levels.

   The study intervention will be implemented during the first clinical assessment, and consequently, primary composite endpoint of "appropriateness of discharge" will be based on the decision of admission/referral vs discharge home during this first clinical assessment, which is more representative of routine clinical practice in each study site.
2. All randomised participants will be also evaluated by an independent study physician in a second clinical assessment, for the implementation of a systematised clinical evaluation (IMCI-based) to uncover any danger signs or severity criteria potentially missed or misinterpreted during the first assessment. This second assessment will also include clinical variables of the clinical scores Paediatric Early Warning Score (ED-PEWS), Lactate enhanced-quick Sequential Organ Failure Assessment (LqSOFA) and Logistic Organ Dysfunction Score (LODS), as well as temperature and oxygen saturation measures. Hence, study clinicians during this second clinical assessment might be able to uncover more symptoms and signs that are admission criteria due to the tools available in the context of this clinical trial. Initially discharged patients from both arms showing a danger sign or other severity criteria during this second assessment will be admitted, as well as those from the intervention arm with sTREM-1 high-risk (red light) and moderate-risk (yellow light) levels, in case that the first clinician might not have adhered to the protocol during the first assessment. On the other hand, this second assessment will not overturn the decision of the first clinician if admission has been decided in case of sTREM-1 levels below 200 pg/mL (green light, low-risk).

This second clinical assessment will guide the ultimate decision on admission/referral vs discharge in order to ensure the safest possible clinical practice in the context of a clinical trial.

Moreover, those participants with respiratory symptoms will be eligible for the respiratory tract infection (RTI) sub-study, where digital lung auscultations, a mid-turbinate nasal swab and a saliva sample will be collected.

Throughout the study, all participants will receive treatment as per the routine clinical practice and SoC for each diagnosis at each study site, administered by clinical staff routinely working in the participating facilities.

All participants will have follow-up evaluations by study clinicians on days 3 and 7 post-enrolment, or at any time in-between in case of clinical deterioration according to caregivers' evaluation. All participants will be also followed-up on day 28 for an interview to follow-up on serious adverse events (SAEs), as well as to collect information on secondary consultations and hospitalisation, or death. A follow-up extra visit at day 91 (month 3) can be conducted for an interview to ask for hospitalisation or death.

Eligibility Criteria:
Inclusion Criteria:

* Age ≥2 months and \<60 months
* Written informed consent from the child's parent or caregiver
* History of fever for ≤7 days OR hypothermia (i.e., axillary temperature \<35.5ºC) OR suspected severe infection (e.g., in children with moderate or severe acute malnutrition).
* Lives within the catchment area of the study facility and must intend to continue to reside there for the duration of the study
* For the RTI sub-study only: presence of respiratory symptoms compatible with RTI.

Exclusion Criteria:

* Weight less than 2.5kg
* Main reason for consultation is an injury, trauma or acute poisoning
* Enrolled in another clinical trial testing a new drug
* Enrolled in a vaccine trial in the last 3 months.
* Any other condition determined by the investigators that makes it unlikely that the participant would complete the study