Diagnostic accuracy of RISK6 assay in childhood pulmonary TB.

Background: The WHO recently updated the target product profile (TPP) for TB identification at the peripheral level to guide test development.

Methods: We conducted a prospective diagnostic accuracy study among outpatients under 15 years old with presumed pulmonary TB at the International Centre for Diarrheal Disease Research, Bangladesh (icddr,b) Dhaka Hospital. We evaluated the accuracy of the RISK6 assay and performed a cost-per-TB case identification analysis.

Results: Of 365 enrolled children, 68 had microbiologically confirmed TB, 94 had unconfirmed TB and 203 were unlikely to have TB. RISK6 did not meet the TPP for TB diagnosis in children but in presumptive pulmonary TB individuals ≤ 12 months, the assay outperformed (32/42) both the Mantoux test (7/42) and chest X-ray (11/42) in correctly referring individuals for confirmatory testing. RISK6, alone or in combination with Mantoux test, was the most cost-effective strategy for identifying and confirming TB, with a cost as low as $US132.00 in children > 12 months.

Conclusion: Although RISK6 did not meet the WHO TPP for TB diagnosis, it shows promise as a triage test, especially for children ≤ 12 months, and could serve as a decision-support tool in integrated treatment algorithms recommended by the WHO.