The Brief Case: False-Positive Rapid Malaria Antigen Test Result in a Returned Traveler.
A previously healthy 43-year-old female presented to her primary care physician with a 13-day history of recurrent nightly fevers (100°F to 101°F), nonproductive cough, and respiratory congestion. She was prescribed azithromycin, albuterol, and benzonatate. She presented to the emergency center 2 days later without improvement and at that time reported night sweats. She had recently traveled to Thailand, Laos, Cambodia, and the United Arab Emirates. The nightly fevers began 11 days after returning home. She acknowledged being bitten by mosquitoes throughout her travels and did not take malaria prophylaxis.
Upon presentation, she was febrile (100.4°F) and tachypneic; right basilar rhonchi were noted. Chest X ray demonstrated multiple nodular lower right lobe airspace opacities. Laboratory evaluation showed mild leukocytosis with absolute neutrophilia, thrombocytosis, and mildly elevated alkaline phosphatase and alanine aminotransferase levels. Meropenem and doxycycline were started for community-acquired pneumonia and melioidosis, given her travel history to Southeast Asia. Additionally, atovaquone-proguanil was started, and a blood parasite examination was performed, including microscopy (thick and thin blood films) and a BinaxNOW malaria antigen test (BinaxNOW; Alere, Scarborough, ME). BinaxNOW was weakly positive for Plasmodium falciparum antigen and negative for pan-malaria antigen (Fig. 1). No parasites were identified by microscopy. Over the next 24 h, two additional blood parasite examinations were performed, both yielding results identical to the initial results. Her condition rapidly improved; all bacterial cultures were negative, and she completed a 3-day course of atovaquone-proguanil. Her antibacterial therapy was changed to oral levofloxacin to complete a 5-day course of therapy.