Session: Poster Session: Malaria and Babesia
Sunday, October 26, 2008: 12:00 AM
Room: Hall C
Background: Microscopic examination of blood is the main diagnostic tool in malaria assessment. This method depends on observer’s expertise. This exam is less sensitive when the parasite load is low. A study was undertaken to evaluate the diagnostic accuracy of an antigen test and a PCR assay. Methods: Methods. 164 blood samples from 147 patients with suspected malaria were examined. All were submitted to real-time PCR TaqMan for Plasmodium spp., and subsequent PCR typing at species level. Moreover, microscopy and antigen detection (Binax Now®) were performed on 108 and 91 samples, respectively. Results: The positivity rate with PCR was 40.2%, with antigen test was 36.3%, and with microscopy was 22.2%. The agreement between PCR and antigen detection was higher (97.8%; kappa = 0.953) than between antigen detection and microscopy (89.6%; kappa = 0.755), and between microscopy and PCR (88.9; kappa = 0.727). The linear regression between log-transformed parasite count and PCR quantitative signal (Ct, cycle threshold) was significant with r-squared = 0.785 (figure). With a PCR Ct >34 the microscopy was often negative. Conclusions: PCR and antigen test appeared more sensitive than microscopy. A clear correlation was found between parasite count by microscopy and PCR signal as Ct.