Clinical Evaluation of the PANDAA Lassa Virus RT-PCR Assay in Sierra Leone

In the dense forests and bustling towns of West Africa, a silent and dangerous virus circulates, waiting for the right moment to strike. This is the Lassa virus, the cause of Lassa fever, a disease that can turn a simple fever into a life-threatening hemorrhagic illness. The virus hides in the urine and droppings of a common rodent, the multimammate rat, and spreads to humans when that contamination touches food, surfaces, or is breathed in as dust. While many people who catch the virus feel only mild symptoms or nothing at all, for others, the illness is severe and deadly, claiming thousands of lives every year across the region. The greatest challenge in fighting this disease is not just treating the sick, but knowing who is sick in the first place. Early symptoms look like many other common fevers, making it impossible to tell a Lassa infection apart from malaria or typhoid without a laboratory test.

To find the virus, scientists rely on molecular tests that hunt for the virus's genetic code, a string of instructions that acts like a unique fingerprint. However, the Lassa virus is a master of disguise; it changes its genetic code constantly, evolving into different lineages that can look very different from one another. A test designed to catch one version might miss another entirely, much like a key that fits only one specific lock. Because of this, laboratories often need to run multiple tests or use complex methods to ensure they do not miss an infection. In Sierra Leone, where the disease is a constant threat, researchers are always looking for better tools: tests that are fast, reliable, and simple enough to work in busy hospitals with limited resources.

A team of researchers recently put a new, experimental tool to the test against the current gold standard used in the region. They compared a widely used commercial test, known as RealStar, with a newer method called PANDAA. The RealStar test is a trusted workhorse that looks for the virus in two different places within its genetic code to reduce the chance of a miss, but this safety feature comes at a cost: it requires running two separate reactions for every single sample, using more materials and time. The PANDAA test, developed by a different company, takes a different approach. It uses a clever design that allows it to adapt to the virus's changing shape, looking for the virus in a single reaction step. The researchers wanted to see if this single-step method could match the accuracy of the two-step method while offering a simpler workflow.

To find out, the team gathered 94 frozen blood samples from patients who had been suspected of having Lassa fever at the Kenema Government Hospital in Sierra Leone. These samples had been collected over a period spanning from early 2023 to late 2025. The researchers re-extracted the genetic material from these stored samples and ran them through both the RealStar test and the PANDAA test. They were looking for a match: did both tests agree on who had the virus and who did not? Out of the original 94 samples, 79 provided clear, usable results from both machines, allowing for a direct comparison.

The results showed that the two tests generally agreed with each other. In about 87 percent of the cases, both tests gave the same answer. When the researchers looked specifically at the samples that the trusted RealStar test had identified as positive, the new PANDAA test agreed with it about 78 percent of the time. This means that in roughly one out of every four cases where RealStar found the virus, PANDAA missed it. However, the new test was very good at confirming when the virus was absent; it agreed with the negative results of the RealStar test more than 93 percent of the time. The researchers calculated that the two tests had a strong level of agreement overall, suggesting they are measuring the same thing, even if they do not always catch every single infection in the same way.

There were ten samples where the two tests disagreed. In three of these cases, the new PANDAA test said the virus was present while the RealStar test said it was not. In the other seven cases, the RealStar test found the virus while PANDAA did not. The researchers noted that the samples where PANDAA missed the virus tended to have lower amounts of viral genetic material, suggesting the new test might struggle when the virus is present in very low numbers. Conversely, the three samples where PANDAA found the virus but RealStar did not might represent cases where the virus had changed its genetic code enough to hide from the older test, or they could be false alarms. Because there was no third, perfect test to decide who was truly infected, the researchers could not definitively say which test was right in these specific instances.

Despite the fact that the new test did not catch every single positive case that the older test found, the researchers highlighted a significant practical advantage. The PANDAA test performs its entire analysis in a single reaction well, whereas the RealStar test requires two separate reactions for each person. This difference means that the new test could potentially use less reagent and run through more samples faster, a crucial benefit during an outbreak when laboratories are overwhelmed. The study concluded that while the PANDAA test shows promise and offers a simpler, more efficient way to test, it is not yet ready to replace the current standard. The researchers emphasized that the test needs further refinement and larger studies to ensure it can reliably detect the virus across all its different forms before it can be used widely in clinical settings. For now, it remains a hopeful step forward, a tool that simplifies the process but still needs to prove it can catch every case as well as the established methods.