P-1596. Comparative Evaluation of Real-Time PCR, Antigen Detection Test, and Microscopy for Malaria Diagnosis
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.
Carlo Mengoli, M D1, Ettore De Canale, M D2, Franco Busolo, Ph D3, Giorgio Palu', M D3, Maria Biasolo, Ph D3 and  C. Mengoli, None., (1)Department of Histology, Mcrobiology, and medical Biotechnology, (2)Azienda Ospedale, (3)University of Padua


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