Backgrounds:

The diagnosis of pulmonary tuberculosis (TB) remains difficult in young children. Rapid biomarker-based tests using non-sputum samples are needed. The role of biomarkers in saliva for diagnosing TB in children has not been fully explored.

Methods

We conducted a review of available studies on the use of host-based salivary biomarkers for diagnosing active pulmonary TB in children and adults.

Results:

We found nine studies on salivary host diagnostic biomarkers, one of which involved children. Three studies evaluated the diagnostic performance of antibodies in saliva to antigens of Mycobacterium tuberculosis, with disappointing results. Six studies measured salivary levels of selected cytokines, growth factors, enzymes and other proteins and found that combinations of these markers showed potential in reaching WHO-endorsed performance criteria for a TB triage test. An eight-marker biosignature comprising of salivary granzyme A, growth differentiation factor 15, serum amyloid A, epithelial-neutrophil activating peptide 78, plasminogen activator inhibitor-1, IL-12(p40), IL-13 and IL-21, was most promising and had a sensitivity of 93% and specificity of 100%.¹

(1) Jacobs et al. Diagnostic Potential of Novel Salivary Host Biomarkers as Candidates for the Immunological Diagnosis of Tuberculosis Disease and Monitoring of Tuberculosis Treatment Response. PLoS One. 2016.

Conclusions/Learning Points:

Saliva could be a valuable diagnostic specimen for diagnosing pulmonary TB in children, however little research in this population exists. Based on adult data, combinations of cytokines and other proteins demonstrate promise as new triage tests for TB. Given the differing TB immune response in children, studies in paediatric populations are now needed. The ready availability of saliva and non-invasive nature of collection is especially appealing for young children. Future directions and suggestions for technologies for salivary biomarker discovery and point-of-care test development are discussed.