article · PLoS neglected tropical diseases
Standard trachoma prevalence surveys rely on clinical grading, which can lose accuracy in low-prevalence environments as elimination targets approach. To assess more sensitive diagnostic alternatives, expenditure records from 2022 across four districts each in Tanzania and Mozambique were analysed. The investigation evaluated the financial impact of augmenting standard grading with ocular swabs for Chlamydia trachomatis testing and dried blood spots for serology. Adding these tools raised survey costs per cluster in both countries. However, the enhanced methods were also more effective at detecting trachoma indicators. In Tanzania, ocular swabs proved to be the most cost-effective addition, whereas dried blood spots were the most cost-effective choice in Mozambique. Combining both methods proved less cost-effective than using either one alone. Diagnostic sensitivity was identified as the primary factor influencing overall cost-effectiveness.
As countries near the elimination of trachoma, clinical examinations alone may yield errors due to declining accuracy in low-prevalence settings. Providing evidence on the financial feasibility and diagnostic performance of ocular swabs and blood spots enables public health agencies to deploy resources efficiently while sustaining reliable disease surveillance.
This applied health economics research directly informs public health programmes, diagnostic laboratories, and disease elimination initiatives deciding on surveillance protocols. While the testing methods are tested in field settings and ready for programme adoption, the findings serve as policy and operational guidance for procurement rather than presenting a commercial product or service pathway.
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BACKGROUND: Accurate methods to measure trachoma prevalence are critical to monitor progress and guide mass drug administration as countries near elimination. Currently, countries conduct trachoma prevalence surveys via clinical examination using the simplified trachoma grading system. Grading can have reduced accuracy in low prevalence settings, potentially resulting in errors. Adding ocular swabbing and Chlamydia trachomatis (Ct) infection testing and dried blood spot (DBS) collection and testing can be more sensitive and specific methods for trachoma identification, with potential cost-saving and information benefits. While previous studies have examined the costs of trachoma prevalence surveys, we present the first costing and cost-effectiveness analysis of enhanced trachoma prevalence surveys with ocular swabs and DBS in addition to grading. METHODOLOGY/PRINCIPAL FINDINGS: We calculated the incremental financial cost of enhanced trachoma prevalence surveys with swabs, DBS, and grading using expenditure records from four districts in Tanzania and four districts in Mozambique in 2022. In Tanzania, the cost per cluster of an enhanced survey was $2,337.39 compared to $459.75 for a standard survey. In Mozambique, the cost per cluster of an enhanced survey was $2,147.12, compared to $1,381.46 for a standard survey. We calculated the incremental cost-effectiveness ratio for each method, defined as the ratio of incremental cost to additional instances of trachoma indicators identified, and explored variation in cost-effectiveness via sensitivity analyses. Adding swabs, DBS, or both was cost-increasing and more effective at identification of trachoma indicators than grading alone. In Tanzania, swabs were the most cost-effective method, while DBS was more cost-effective in Mozambique. Swabs and DBS were less cost-effective when combined than individually. The main factor determining cost-effectiveness was sensitivity. CONCLUSIONS/SIGNIFICANCE: Adding swabs or DBS to trachoma prevalence surveys can be viable, cost-effective methods for identifying trachoma indicators. The additional costs are commensurate with additional information that would support elimination efforts.
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DOI: 10.1371/journal.pntd.0013257
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