QUESTION
I have never been diagnosed with malaria but returned from Turkey in 2007 (P. Vivax endemic area; Diarbykar & Mardin areas). My symptoms were consistent with malaria and I have now had 5 relapses since then, averaging one occurrence per year. I now have impaired kidney functioning and I am uncertain if this could be because of undiagnosed malaria? Would the PCR blood test at anytime be an option to conclusively rule out malaria or would blood need to be drawn during an actual relapsing event?
ANSWER
You have certainly done your research! It’s great to hear from someone who is so well informed about the risk areas they traveled too and the diagnostic options. You’re right in thinking that PCR is only appropriate during an active relapse; while the malaria parasites are dormant in the liver (called hypnozoites, in that form), they are extremely hard to detect. One option could be to investigate the possibility of taking a test to look for antibodies to the P. vivax parasite. These tests are often referred to as ELISAs (enzyme-linked immunosorbent assays) and they can sometimes be useful for testing for malaria in between relapses because the antibodies your body produces against the malaria parasite during the relapse phase can stick around in the blood for weeks, or even months or years. Therefore these tests are not very useful for people in endemic areas (who may always have these antibodies, regardless of their current infection status) but for travelers who have been exposed a limited number of times, this test may be able to say whether you have at some stage been infected with P. vivax; together with your clinical history, this will provide strong evidence to your doctor that you might need to discuss the possibility of taking primaquine, the drug which can kill the dormant hypnozoites and prevent further relapse.
Thanks for the response. As for as the informed part…well…hindsight is 20/20! I was told by a friend of a friend (Infectious Disease Doc), that “this malaria PCR test actually measures if the malaria DNA is in your system, it is NOT an antibody test. This is a relatively new test, probably only commercially available in the last year or two.” So…as you can see, something isn’t tracking? Can you confirm a recent PCR test that measures “DNA” and not “antibodies”? THANKS!
Yes, that is correct – the PCR test looks for the actual DNA of the malaria parasite, which is why it can only be used during an active infection. After the malaria infection is cleared, there will be no more malaria DNA in the patient’s blood, so the PCR test will come up negative. However, antibodies to the malaria parasite can persist for months or even years after the infection has been cleared – so, even after a patient has been successfully treated, an antibody test might still come up positive. This is useful for people who are interested if they have had malaria in the past, but because of the lack of time specificity, antibody tests are not very useful for diagnosing an active case of malaria, particularly if a person lives in an endemic area and thus has likely been exposed numerous times to malaria. You are also right in noting that the PCR test is relatively new – I’m actually not sure how available they are yet commercially, but they are usually quite expensive to have in a hospital setting given the time, expertise and reagents required to run the test.