Sputum and tongue swab molecular testing for the in-home diagnosis of tuberculosis in unselected household contacts: a cost and cost-effectiveness analysis

Abstract

Background: Delayed and missed diagnosis are a persistent barrier to tuberculosis control, partly driven by limitations associated with sputum collection and an unmet need for decentralized testing. Household contact investigation with point-of-care testing of non-invasive specimens like tongue swabs are hitherto undescribed and may be a cost-effective solution to enable community-based active case finding.

Methods: In-home, molecular point-of-care testing was conducted using sputum and tongue specimens collected from all household contacts of confirmed tuberculosis cases. A health economic assessment was executed to estimate and compare the cost and cost-effectiveness of different in-home, point-of-care testing strategies. Incremental cost effectiveness ratios of strategies utilizing different combination testing algorithms using sputum and/or tongue swab specimens were compared.

Findings: The total implementation cost of delivering the standard of care for a 2-year period was $84 962. Strategies integrating in-home point-of-care testing ranged between $87 844 - $93 969. The cost-per-test for in-home, POC testing of sputum was the highest at $20·08 per test. Two strategies, Point-of-Care Sputum Testing and Point-of-Care Combined Sputum and Individual Tongue Swab Testing were the most cost-effective with ICERs of $543·74 and $547·29 respectively, both below a $2,760 willingness-to-pay threshold.

Interpretation: An in-home, point-of-care molecular testing strategy utilizing combination testing of tongue swabs and sputum specimens would incur an additional 10.6% program cost, compared to SOC, over a 2-year period. The increased sample yield from tongue swabs combined with immediate result notification following, in-home POC testing would increase the number of new TB cases detected and linked to care by more than 800%.

Figure 1:

Simplified decision analytic model The diagram shows the diagnostic pathway from testing to treatment initiation. ILTFU: Initial loss to follow up refers to HHCs who tested positive but never present for treatment initiation.

Figure 2.

Cost-effectiveness plane of different household contact investigation testing strategies

Figure 3:. Deterministic sensitivity analysis

Tornado diagram, depicting the effect of changing individual model parameters on the ICER when comparing SOC against POC Combined Sputum and Individual Tongue Swab Testing. The diagram depicts the base case ICER of $547 as the difference in ICER between the two strategies to highlight the sensitivity of the ICER value to changes in individual model parameters. Parameters are listed in the order of influence on cost-effectiveness. A low value (blue) indicates that cost-effectiveness has a positive correlation with the parameter value, whereas a high value (orange) has a negative correlation.