Use of dipstick tests for the rapid diagnosis of malaria in nonimmune travelers

Background: Swift diagnosis of falciparum malaria in nonendemic areas is frequently complicated by lack of experience on the side of involved laboratory personnel. Diagnostic tools based on the dipstick principle for the detection of plasmodial histidine-rich protein 2 (HRP-2) (ICT Malaria P.f.®) and parasite-specific lactate-dehydrogenase (pLDH) (OptiMal®), respectively, have become available for the qualitative detection of falciparum malaria. Methods: In order to evaluate currently available assays, a series of studies was conducted: sensitivity and specificity were evaluated by investigation of specimens from 231 febrile returnees from endemic areas, cross reactivity in patients with rheumatoid factor (RF) was assessed among 92 patients from a rheumatology unit, and the quality of dipstick self-use by febrile travelers was tested in Kenya. Results: Whereas the test kit based on the detection of HRP-2 performed with a sensitivity of 92.5% and a specificity of 98.3%, the kit for the detection of pLDH showed a sensitivity of 88.5% and a specificity of 99.4%. Cross-reactions with sera positive for rheumatoid factor occurred in 6.6% with the ICT Malaria P.f.®, and in 3.3% with the OptiMal® test. Only ICT Malaria P.f.® was tested for quality of self-use among travelers. This dipstick assay was performed successfully by 67 patients (68.4%), but 31 (31.6%) were unable to obtain a result. Conclusion: Dipstick tests have the potential of enhancing speed and accuracy of the diagnosis of falciparum malaria, especially if nonspecialized laboratories are involved. However, microscopical testing remains mandatory in every single patient with the possible diagnosis of malaria. Self-use of dipstick tests for malaria diagnosis by travelers should only be recommended after appropriate instruction and training, including a successful performance of the test procedure.