[Primary evaluation on the application of nested/multiplex PCR in malaria diagnosis and surveillance].

Objective: To compare the usefulness of Tag-primer nested/multiplex PCR (UT-PCR) method with microscopy in malaria diagnosis and surveillance.

Methods: 400 blood smears and blood samples on filter paper were taken from febrile patients which were initially diagnosed as malaria or suspected malaria during surveillance in mixed endemic areas of Plasmodium falciparum (Pf) and P. vivax (Pv) in Hainan and Yunnan provinces and a malaria-controlled area in Guangxi Zhuang Autonomous Region. The initial test results of both UT-PCR and microscopy for the 400 samples were compared under double blind condition. Blood smears with discrepant results between the two methods were retested by an experienced microscopist, and also repeated by UT-PCR for 2-3 times. The sensitivity and specificity of the two methods were evaluated following the Tjitra's method.

Results: Among the 400 blood samples, 234 were found plasmodium-positive by microscopy with 125 Pf and 109 Pv; 235 were positive by UT-PCR including 124 Pf, 109 Pv and 2 mixed infection. Altogether, the coincidence between the two methods stood for 92.5 % (370/400), including 154 negatives and 216 positives (Pv 117, Pf 99). 25 samples with discrepancy from the initial detections were retested, which covered 11 microscopy negative and PCR positive, 10 microscopy positive and PCR negative, 3 microscopy Pf positive and PCR Pv positive, 1 microscopy Pv positive but PCR mixed infection. 15 of the 25 samples showed same UT-PCR results, 7 "false positives" and 3 "false negatives" . Therefore, the sensitivity and specificity of UT-PCR was 99.6% and 98.8% respectively.

Conclusion: As a diagnosis method, UT-PCR is useful for confirmation of malaria diagnosis and differentiation of Plasmodium species, also for improving the effectiveness and quality of malaria surveillance.