Over the past 15 years, global malaria mortality has declined by 48% largely due to expanding coverage of effective malaria control interventions such as insecticide-treated bed nets, indoor-residual spraying, and artemisinin-based combination therapy (ACT) [1, 2]. The health benefits of these tools, however, often depend on people’s decision to use them and to do so appropriately [3, 4]. Understanding individuals’ subjective expectations about their illness, about the accuracy of diagnostic technologies, and about the effectiveness of treatment could provide insight into the uptake and use of medications such as artemisinin-based combinations [5].

Most countries with Plasmodium falciparum adopted ACT as the first-line treatment for malaria between 2001 and 2008 [6]. While ACT is very effective in treating the disease, the artemisinin-based combinations are often used to treat febrile illnesses that are not malaria [7, 8]. This may delay appropriate treatment for the illness, waste valuable drugs, and also increases the risk of parasites developing resistance to ACT [9, 10].

The widespread overuse of ACT is partly explained by the fact that many febrile individuals are presumptively treated for malaria based on symptoms and do not receive a malaria diagnostic test [7, 11]. Since 2010, when the World Health Organization recommended that all suspected malaria cases receive a confirmed diagnosis before ACT, testing rates in the public health sector have increased dramatically [12]. However, in many contexts, health workers continue to treat individuals who test negative with anti-malarial drugs [13, 14]. In addition, between 30 and 70% of all anti-malarials are distributed in private pharmacies and drug stores where diagnostic testing is rare [15, 16]. Therefore, there has been growing interest in expanding malaria diagnostic testing to private drug shops [17–20]. This has become increasingly feasible due to the commercial availability of malaria rapid diagnostic tests (RDTs), which have simplified malaria testing and provide very accurate results [21, 22].

In order for testing in private drug shops to improve ACT targeting, individuals who suspect malaria need to both choose to get tested and to treat according to the test result. These decisions are likely influenced not only by the relative costs of testing and treatment, but also by perceptions about the accuracy of a malaria diagnostic test [4, 23]. While qualitative studies have examined community attitudes towards testing, there is little evidence on how people learn about the benefits of malaria testing [24–26]. This study hypothesized that individuals’ experiences at formal health facilities influences their beliefs about malaria testing and treatment. The analysis investigates how health workers’ adherence to malaria case management guidelines is associated with individuals’ (or their caregivers) beliefs about the likelihood their illness was malaria, and their beliefs about the effectiveness of ACT.

The benefits of expanding access to malaria testing will only be realized if suspected malaria cases receive a confirmed diagnosis before treatment. This study has three main results. First, most (>80%) individuals visiting a formal health facility in this context were tested for malaria, and ACT use was associated with the diagnostic test result. Second, individuals’/caregivers’ beliefs about whether their illness was malaria were independently associated with both the diagnostic test result and also with whether the sick individual was treated with ACT. Third, malaria-negative individuals who were incorrectly treated with ACT had lower confidence in the drug than other individuals treated with ACT.

Although this study finds that malaria testing is being commonly used in formal health facilities, and high rates of ACT use for malaria-positive individuals, approximately 50% of individuals who tested negative for malaria were still treated with an ACT. This suggests that either health workers lack confidence in the negative test result, or that they do not have the necessary skills, training or support to confidently provide an alternative diagnosis. This result corresponds with evidence from other clinical contexts of low adherence to a negative test result [13, 14]. Moreover, as in other studies, individuals and caregivers also expressed greater confidence in a malaria positive test result than a negative test result [26, 38], perhaps because a positive result confirms individuals’ expectations of having malaria [39, 40]. In the case of RDTs, adherence to the test may increase over time as both health workers and individuals gain exposure to the technology [41, 42]. In some contexts, increased training of health workers, or targeting individuals’ malaria knowledge and perceptions has been shown to improve test adherence [43–46].

This is one of a few studies to examine how beliefs about malaria are associated with diagnostic testing and with treatment [23, 47, 48]. The results show that individuals’/caregivers’ beliefs about malaria likelihood are associated with the malaria test result, though this is likely to be a combination of differences in beliefs prior to testing and updating of beliefs based on the test result. However, the results also suggest that, regardless of test status, individuals/caregivers were more likely to believe that the illness was malaria when the sick individual was treated with ACT. This may be because being prescribed an ACT is perceived as synonymous with a diagnosis [49] or because treatment reinforces beliefs that the illness was malaria (particularly if the illness resolved following treatment).

Lastly, this study finds that individuals who tested negative and were treated with ACT had lower confidence in effectiveness of the drug than other individuals who were treated with ACT. This suggests that individuals’ whose illness did not resolve with ACT concluded that the drugs were not effective in treating malaria. These results coincide with evidence from Tanzania, which suggests that high rates of malaria mis-diagnosis hampers patient learning about ACT effectiveness [50]. It is also possible that respondents interpreted the question about drug effectiveness specifically in terms of treating the current illness (and not malaria more generally) and may have recognized that the ACT they took was not effective for malaria-negative individuals because their illness was not malaria. However, 75% of respondents for malaria-negative individuals who were treated with an ACT still believed that it was “likely” or “very likely” that the illness was malaria.

There are several limitations to this study. First, although individuals were visiting a health facility, individual/caregiver confidence in testing may have influenced whether the sick individual was tested for malaria and adherence to the test result. However, there are several pieces of evidence to suggest that the testing and treatment decisions were made primarily by the health worker. First, regardless of test status, more than 84% of individuals obtained ACT either at the health facility or at a pharmacy with a prescription (Additional file 4). This suggests that, in most cases, ACT was prescribed by the health worker. Second, there is no evidence that individuals’/caregivers’ confidence in a malaria test result is associated with the probability of being tested (Additional file 5) or with adherence to a negative test result (Additional file 6). It is important to note, however, that confidence in the test was measured after individuals had already sought care for their illness, and testing and treatment may have affected confidence in testing. The survey did not collect information on individual/caregiver beliefs prior to seeking care and, therefore, it is not possible to examine how these beliefs are associated with testing and treatment.

A second limitation is that the study relies on individuals/caregivers’ self-reports of their malaria test result, and individuals treated with ACT may have assumed that they tested positive for malaria. However, when the analyses are limited to the 414 (39%) individuals who had a record for their test result (if they reported being tested), and who had the packaging of their ACT observed (if they reported taking ACT) results are similar though the confidence intervals are wide due to the smaller sample size (Additional files 7, 8).

Third, since beliefs about ACT effectiveness were only elicited for individuals treated with ACT, it is not possible to test how confidence in the drug is associated with whether an individual was treated with ACT. They survey also did not collect data on the length of individuals’ illness to examine how this correlates with individuals’/caregivers’ beliefs about ACT effectiveness.

Fourth, it is possible that people’s definition of malaria is broader than the biomedical definition of an infection that can be detected by a test and treated with ACT [51]. As a result, a person’s belief about whether the sick individual’s illness was malaria may not necessarily reflect his/her confidence in the test result. However, in a pilot study conducted in the same area, respondents demonstrated awareness of the transmissibility of malaria by mosquitoes and the correct treatment of the illness, suggesting an understanding of the biomedical basis of the disease (unpublished observations).

Lastly, the way people’s beliefs about malaria likelihood and beliefs about ACT effectiveness were dichotomized (“very likely” compared to all others) means that the analysis focuses on the degree to which respondents are fully confident in their response or have some uncertainty. Although the results show that respondents’ certainty about whether the illness was malaria and beliefs about ACT effectiveness vary by their testing and treatment outcomes, it is not possible to say to what extent these differences in beliefs may influence individuals’ future malaria treatment decisions.

The results of this study suggest that health worker non-adherence to negative malaria test results has important implications for individuals’ beliefs about their illness and about treatment. Thus, increasing health workers’ adherence to malaria treatment guidelines—for example by reinforcing their trust in the test or by offering training and support on management of non-malarial febrile illnesses—would not only directly improve ACT targeting, but may also raise people’s confidence in testing and treatment. This could affect whether individuals/caregivers choose to get tested for future illnesses and adhere to the test result, a growing concern as diagnostic testing is expanded to the informal private sector. Further research is needed to understand how individual beliefs about testing and treatment at the end of one illness episode affect treatment behaviors for future illnesses.