Imagine trying to track an invisible enemy—one that moves silently and unpredictably, leaving illness and suffering in its wake. This is the challenge that scientists face when mapping malaria risk. But now, a groundbreaking study led by Dr. Issa Mshani from the Ifakara Health Institute has introduced a new way forward, calling for better diagnostic tools to sharpen the fight against malaria.

Published on the Malaria Journal, the study highlights a crucial issue: current tools used to detect malaria might not be sensitive enough to capture the full picture. When cases go undetected, communities remain at risk, and resources may not reach the places that need them the most.

By using high-sensitivity diagnostic tools, health experts can create more accurate malaria maps, ensuring interventions are targeted effectively. This shift could be a game-changer for malaria control and elimination efforts, helping countries allocate resources wisely and protect more lives. 

Comparing diagnostic tools
The study, conducted in 35 villages across Ulanga and Kilombero districts in southeastern Tanzania between 2022 and 2023, compared three diagnostic methods: rapid diagnostic tests (RDTs), microscopy, and quantitative polymerase chain reaction (qPCR). 

The findings revealed major differences in the effectiveness of these diagnostic tools. RDTs and microscopy whilst cost-effective and widely used, they often missed cases, especially in areas with low malaria transmission. In some villages, their positive predictive value fell below 20%.

In contrast, the qPCR method proved to be much more sensitive, detecting cases missed by the other tools and classifying most villages as moderate to high risk. This was in contrast to RDTs and microscopy, which frequently underestimated the level of risk.

“This study highlights significant fine-scale variability in malaria burden within and between the study districts and emphasizes the variable performance of the testing methods when stratifying risk at local scales,” the scientists noted. 

“While RDTs and microscopy were effective in high-transmission areas, they performed poorly in low-transmission settings, classifying most villages as very low or low risk. In contrast, qPCR classified most villages as moderate or high risk.”

Implications on malaria mapping 
The scientists uncovered notable variability in malaria prevalence, even within small geographic areas. For example, some villages classified as low-risk by RDTs or microscopy were classified as moderate to high risk using qPCR. This discrepancy underscores the risk of misallocating resources or prematurely withdrawing interventions in areas still experiencing significant malaria transmission.

The study also highlighted that adults over 20 years old often harbored low-density infections that went undetected by RDTs and microscopy, further underscoring the need for more sensitive diagnostic tools.

“The findings emphasize that, where precise mapping and effective targeting of malaria are required in localized settings, tests must be both operationally feasible and highly sensitive. Furthermore, when planning microstratification efforts to guide local control measures, it is crucial to carefully consider both the strengths and limitations of the available data and the testing methods employed.”

Addressing implementation challenges of qPCR
While qPCR offers superior accuracy, its high costs, infrastructure requirements, reliance on trained personnel, and lack of portability pose challenges for widespread use in resource-limited settings. 

To address these barriers, the study recommends innovative strategies, such as establishing centralized facilities for qPCR testing, partnering with local research organizations to integrate advanced diagnostic methods, and exploring alternative approaches such as combining hospital, school, and antenatal clinic data or using emerging technologies like saliva-based tests and machine learning.

The scientists cautions against relying solely on less sensitive tools like RDTs and microscopy for decision-making noting how misclassifying areas as low-risk could lead to premature withdrawal of interventions or ineffective resource allocation.

Further research, validation needed
The findings underscore the urgent need for affordable, portable, and sensitive diagnostic tools tailored to malaria-endemic regions. Promising innovations, such as infrared spectroscopy and high-sensitivity RDTs, could revolutionize malaria mapping but require further research and validation.

Issa and the research team urge public health authorities to carefully consider the strengths and limitations of available tools and to prioritize high-sensitivity diagnostics for effective malaria control and elimination efforts. As Tanzania and other countries aim to eliminate malaria, adopting data-driven strategies and improving diagnostic capabilities will be crucial.

Ifakara scientists behind the study
The study was led by a team of scientists from Ifakara Health Institute, with Issa Mshani as the lead author. Francesco Baldini and Fredros Okumu, also from Ifakara, along with Simon Babayan from the University of Glasgow, co-supervised the work. 

Additional contributors from Ifakara include Frank Jackson, Elihaika Minja, Said Abbasi, Nasoro Lilolime, Faraja Makala, Alfred Lazaro, Idrisa Mchola, Linda Mukabana, Najat Kahamba, Alex Limwagu, Rukia Njalambaha, Halfan Ngowo, and Donal Bisanzio.

Read the publication here.