Study reveals critical gaps in how acceptability of tropical disease treatments is measured

A team of researchers examining how public health programs measure whether people will actually accept treatments for neglected tropical diseases has uncovered a troubling gap: there is no agreed-upon way to do it. The finding comes from a scoping review of 40 published studies that attempted to quantify acceptability—the degree to which patients and communities view a treatment as appropriate and worth taking. The work, led by researchers including Duguay, Ost, and Krentel, was published in PLOS Neglected Tropical Diseases in May 2026.

Neglected tropical diseases affect roughly one billion people worldwide, predominantly those living in vulnerable circumstances. These are 21 distinct conditions—ranging from lymphatic filariasis to schistosomiasis to leprosy—that disproportionately burden low-income populations. Treating them requires not just safe and effective medicines, but also the willingness of communities to accept and take those medicines. Yet when researchers set out to measure whether people actually find treatments acceptable, they discovered they were using wildly different methods, making it nearly impossible to compare results across studies or draw reliable conclusions.

The researchers searched five academic databases and identified 1,340 articles. After screening, 40 met their criteria: studies that quantitatively assessed acceptability of pharmaceutical interventions for at least one neglected tropical disease. What emerged was a portrait of methodological chaos. Fourteen studies measured acceptability using multiple questions and established a threshold for what counts as acceptable. Five others used multiple questions but never defined what acceptability actually means numerically. Twenty-two studies—more than half—relied on a single question to capture acceptability, despite widespread recognition that acceptability is a multifaceted construct involving cognitive and emotional responses. Four studies reported measuring acceptability but provided no methodological details whatsoever, leaving readers unable to understand how the researchers arrived at their conclusions.

The inconsistency becomes even more glaring when examining mass drug administration programs, which distribute preventive medicines to entire populations regardless of infection status. These programs target five diseases classified as preventive chemotherapy NTDs: lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiases, and trachoma. Although each disease requires specific medications and each program follows similar implementation strategies, the 16 studies examining acceptability in these programs employed nine different measurement approaches. One study used a composite score of nine acceptability indicators on a four-point scale, with a median threshold of 22.5 out of 36. Another adapted a different framework, using six indicators on a five-point scale. A third employed a three-dimensional mapping technique. The result is that researchers studying essentially the same type of public health intervention cannot meaningfully compare their findings.

Another significant problem emerged: thirteen of the forty studies claimed to measure acceptability but were actually measuring something else entirely—coverage (whether people received treatment) or compliance (whether they swallowed it). These are not the same thing. A person might accept a treatment but face barriers to receiving it. Another might receive it but refuse to take it. Conflating these concepts obscures understanding of why interventions succeed or fail and prevents meaningful improvement.

The gaps extend beyond methodology. Of the twenty-one recognized neglected tropical diseases, only ten appeared in the published literature on acceptability. Eleven diseases—including Buruli ulcer and Chagas disease—have no published studies quantitatively assessing whether people find their treatments acceptable, despite the existence of efficacious medications. The WHO 2030 NTD roadmap mentions acceptability once in 196 pages, calling for "availability, accessibility, acceptability and affordability" of medicines but offering no guidance on how to measure acceptability or integrate it into planning.

This matters because acceptability is one of seven key factors the World Health Organization considers when developing public health recommendations. The stronger the acceptability of an intervention, the stronger the recommendation can be. Yet without standardized measurement, acceptability remains a vague concept—difficult to assess, impossible to compare, and ultimately underutilized in the decision-making process. The researchers argue that developing and adopting a consistent framework for measuring acceptability is essential not only for advancing scientific understanding but for achieving the WHO's goal of eliminating neglected tropical diseases by 2030, particularly in the populations most affected by them.