Rapid Tests Aren't Always Accurate in Testing for HIV, HCV and HBV

Good news and bad news for African countries utilizing rapid tests on their collection of blood samples: while their proficiency in detecting HIV has improved, accuracy in hepatitis B and hepatitis C virus testing remains lacking. This, according to a new report in the US Centers for Disease Control and Prevention (CDC’s) Morbidity and Mortality Weekly Report.

It is standard practice for a blood bank to test their bags for HIV and hepatitis B and C. Though typically, it is performed in a lab setting. That’s not the case in many African countries because it’s not economical due to the volume of samples they collect in a day. While many countries collect high volumes of blood bags in a single day and can send them to a lab to be tested, fewer samples are collected in African countries, and therefore it is cheaper to buy rapid tests—often of dubious quality—and use them instead.

Edward Murphy, MD, MPH, professor of Laboratory Medicine and Epidemiology/Biostatistics at the University of California San Francisco, told Contagion® that his team and others are aware that conditions on the ground are difficult, and there is a lack of equipment and poor training. This leads to more rapid tests being obtained and put to use.

“Rapid tests are useful because they’re easy to do and they can be done out in the field,” Murphy said. “In the kind of general HIV public health area, they’ve been a really good thing… but they were never meant for blood banks.”

These factors combine for a false sense of assurance that even if a lab says they are testing for these infections, there is no way to know for sure that the labs are not inadvertently allowing blood to be contaminated.

As the third study in their ongoing series, Murphy and investigators collected blood samples from 7 African countries between February and September 2017 in order to determine if the samples were correctly or incorrectly classified as positive or negative for the 3 infections. The countries included in the analysis were Ghana, Kenya, Malawi, Mozambique, Nigeria, Rwanda and Tanzania.

The first 2 studies from the team were published in transfusion journals, Murphy explained, and they demonstrated poor results across the board for rapid tests’ ability to correctly test for HIV, hepatitis B and hepatitis C virus.

This time, the study authors showed that rapid tests improved their accuracy for HIV testing. Murphy suspects that this might be due to recent research and developments into rapid tests for HIV, as well as more global attention focused on HIV in Africa. On the other hand, this phenomenon hasn’t happened for hepatitis.

Hepatitis B and C testing showed no significant improvement for rapid testing. Murphy sees 2 reasons for this. One is poor rapid test quality, and the other is possible user error.

“With a rapid test, there’s a lot more user variability,” Murphy explained. “It’s like a pregnancy test. You do a little test and you look at it and then you record the results. None of it is done by a machine so there’s more room for human error and interpretation.”

However, between half and two-thirds of laboratory settings got perfect results for HIV and hepatitis B and C testing.

“What we’re planning to now do is to go back to the labs that did really badly and test them again after the CDC did some remediation,” Murphy added. “They sent some of their people to talk to them, to try to figure out what the problem was. We’ll try to see if things improve in a second round.”