Differential expression of host protein biomarkers among symptomatic clinic attendees finally diagnosed with tuberculosis and other respiratory diseases with or without latent Mycobacterium tuberculosis infection.

Background: There is a need for new tools for the diagnosis of tuberculosis (TB) amongst patients who present at primary health care centers with symptoms suggestive of TB.

Objectives: To assess the abilities of selected blood-based host biomarkers to discriminate between patients who self-presented with symptoms suggestive of TB and were subsequently diagnosed with pulmonary tuberculosis (PTB), other respiratory diseases (ORD) with latent Mycobacterium tuberculosis infection (ORD_LTBI) or ORD without latent infection (ORD_NoLTBI).

Methods: Presumptive TB patients (n = 161) were enrolled at a TB Clinic in Kampala, Uganda, and blood was collected. Participants were later classified as having PTB or ORD using standard microbiological confirmatory tests. Patients with ORD were subsequently classified as having LTBI or no LTBI using the QuantiFERON Gold-plus test. The concentrations of 27 host biomarkers were evaluated in patient sera using the Luminex platform, followed by an evaluation of their abilities to discriminate between PTB, ORD_LTBI, and ORD_NoLTBI.

Results: Multiple host biomarkers including IP10, IL6, IL2, IL1β, TNFα, IFNγ, and IL12p70, were significantly different between patients with PTB (n = 55), ORDs (n = 106), and between PTB and the two ORD sub-groups. A bio-signature comprising IP10, IL6, TNFα IL1β, IL1ra, and IL12p70 best diagnosed PTB disease, with an area under the ROC curve of 90.

Conclusion: We identified host biomarkers that discriminated between different M.tb infection states amongst patients who presented with symptoms requiring investigation for TB. The biomarkers that showed diagnostic potential in our study may be considered as additional candidate markers for future active PTB rapid screening tests.