| Summary: | <p>Abstract</p> <p>Background</p> <p>The use of malaria rapid diagnostic tests (RDTs) has been widely advocated to improve <it>Plasmodium falciparum </it>diagnosis, especially in settings where quality microscopy is not available. RDTs based on the detection of histidine-rich protein 2 (HRP-2) can remain positive for several weeks after an infection is cured, due to the persistence of HRP-2 antigens. As a result, test specificity may vary between age groups with different prevalence of <it>P</it>. <it>falciparum </it>infection.</p> <p>Methods</p> <p>A community-based cross-sectional survey, carried out in southern Tanzania in July and August 2004, evaluated the performance of the Paracheck Pf in comparison with microscopy (number of <it>P. falciparum </it>parasites/200 leucocytes). A sample of 598 individuals living in an area of intense malaria transmission had demographic data collected before an RDT was performed. HRP-2 test sensitivity, specificity, positive and negative predictive values were calculated and compared between distinct age groups, using microscopy as "gold standard".</p> <p>Results</p> <p>The overall malaria prevalence was 34.3% according to microscopy and 57.2% according to the HRP-2 test. The HRP-2 test had a sensitivity of 96.1%, a specificity of 63.1%, a positive predictive value of 57.6% and a negative predictive value of 96.9%. The test sensitivity was higher (ranging from 98% to 100%) amongst people less than 25 years of age, but decreased to 81.3% in older adults. The HRP-2 test specificity varied between age groups, ranging from 25% among children of five to nine years of age, to 73% among adults aged 25 or more. The test positive predictive value increased with malaria prevalence, while the negative predictive value was consistently high across age groups.</p> <p>Conclusions</p> <p>These results suggest that the performance of HRP-2 tests in areas of intense malaria transmission varies by age and the prevalence of <it>P. falciparum </it>infection. The particularly low specificity among children will lead to the over-estimation of malaria infection prevalence in this group.</p>
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