Wrong Sample Dispensing May Cause False Positive Malaria Test

Abstract

Both false positive (FP) and false negative are known limitations of any diagnostic test. Malaria parasite (MP) rapid diagnostic tests (RDTs) may give FP results due to interference by substance in blood sample. We detected a FP in a MP RDT for first time in 36-year-old female whole blood donor due to incorrect sample dispensing technique. As per manufacturer’s instructions, while allowing all kit components and blood specimen to come to room temperature before testing, blood samples usually separate into lower layer of red blood cells (RBC) and upper layer of plasma. Technician performing the test took the sample from the bottom of the vacutainer thus taking RBC instead of whole blood (WB-recommended by manufacturer). This test showed reactive result and as per our standard protocol was retested to confirm the result. This second test was performed after re-mixing the same sample, which now tested as non-reactive sample, buffer and other kit component mix-up were ruled out. Repeated test on another sample of same donor produced same results. Thick and thin peripheral blood smear examination for malaria was found negative. This case highlights wrong MP RDT result due to wrong sample dispensing.

Keywords

• malaria parasite
• rapid diagnostic tests
• rheumatoid factor