The CAP Today monthly Q & A column allows readers to submit their pathology-related question for reply by appropriate medical consultants. January's Q & A column features a response from Mayo Clinic's Bobbi Pritt, M.D., regarding testing for malaria.
Q. Our laboratory recently received an order for malaria thick + thin smear for an asymptomatic patient for the purpose of travel visas. The patient’s travel history is not readily available to the lab, and it appears some countries do require a “malaria test” before issuing visas to visitors. I have concerns about the value of a thick/thin smear in this clinical setting. Would other laboratory screening methods be more appropriate in asymptomatic, likely low-risk patients?
A. We agree with your assessment that testing for malaria in an asymptomatic individual, especially without a relevant travel history, has questionable benefit. However, if it is required for visa purposes, then we would recommend performing either a traditional thick film or a malaria PCR assay. In general, malaria PCR has greater sensitivity than conventional blood film morphology and therefore would have the highest likelihood of detecting very low levels of parasitemia, although its availability is limited to reference labs and the Centers for Disease Control and Prevention. You may wish to check the requirements of the specific country that is requiring this testing to ensure that it does not have a preferred test. Thick and thin blood films are probably acceptable in most if not all cases.