WHO warns that faint lines on rapid tests may cause malaria misdiagnosis
Malaria rapid diagnostic tests are under the spotlight at the World Health Organization (WHO), after reports that devices showed positive faint lines for patients with a confirmed malaria infection.
The WHO said that reports came in last year about positive faint lines. These were predominantly observed in patients with low parasitemia, a term used for the small presence of parasites in the blood. However, some patients with higher parasitemia also generated faint test lines – patients in this group would usually produce strong bands on rapid tests.
WHO did not immediately respond to Medical Device Network's request for further information on which manufacturers were affected by the WHO medical product alert on 31 March.
Abbott, Advy Chemical, and Zephyr Biomedicals, amongst others, have tests that meet the WHO's regulatory standards, as per the agency's product prequalification database. Exact data on the most widely used brand is difficult to ascertain. In a British Medical Journal (BMJ) study of 85,000 participants across various countries in Africa, Abbott's SD Bioline Malaria Ag Pf was the most common rapid diagnostic test brand.
False negative tests usually lead to misdiagnosis, and delays in diagnosis and treatment. The faint test lines, which increase the risk of false negative tests, have led to the issues in recent reports to the WHO.
'In circumstances where misdiagnosis occurs, the potential for harm, such as death or serious deterioration in health, is increased,' the WHO said in a statement.
Rapid diagnostic tests have become a key framework for malaria diagnosis. They are an accessible alternative to disease diagnosis by microscopy, where laboratory services might not be available.
The in vitro diagnostic works by detecting specific antigens produced by malaria parasites in the blood of infected individuals. Depending on the manufacturer, tests can either detect one or multiple species. Their use has led to a sustained increase in testing rates and more accurate tracking of malaria cases.
According to the medical product alert, incidents were reported in several countries for various products detecting both Plasmodium falciparum and Plasmodium vivax, and products detecting Plasmodium falciparum and pan species.
Those who use the tests in national control programmes have been recommended to ensure proper transport and storage, up-to-date training, and visual acuity requirements for users. Testing sites should also be contacted to seek feedback on unusual trends, as well as supporting manufacturers.
As per WHO recommendations, any test line – no matter its faintness – should be recorded as a positive test. However, there have been calls from academia to improve the detection of these bands. For example, some evidence suggests that these bands are sometimes too faded to be seen in poor lighting, a problem in low and middle-income territories.
There were an estimated 263 million cases of malaria in 2023. The WHO African region carries the highest disease burden, accounting for 94% of cases and 95% of deaths.
WHO has been grappling with the loss of funding to key malaria programmes in Africa following the suspension of USAID funding. Efforts to fight other infectious diseases such as mpox and tuberculosis have also been impacted.
"WHO warns that faint lines on rapid tests may cause malaria misdiagnosis" was originally created and published by Medical Device Network, a GlobalData owned brand.
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