Comparison of Babesia microti Real-Time Polymerase Chain Reaction Assays for Confirmatory Diagnosis of Babesiosis

Abstract Babesiosis is an emerging tick-borne disease caused by apicomplexan parasites of the genus Babesia. Most human infections in the United States are caused by Babesia microti, but other infection-causing Babesia parasites have been documented as well. Polymerase chain reaction (PCR)–based methods can be used to identify this parasite to the species level. In this study, published real-time PCR assays for the specific detection of B. microti were evaluated against conventional PCR for their analytical performance. All evaluated real-time PCR assays had comparable dynamic range and amplification efficiency, but the sensitivity and specificity varied. The best performing test, a TaqMan assay targeting the 18S ribosomal RNA gene, was further evaluated for diagnostic performance using blood specimens submitted to the Centers for Disease Control and Prevention for parasite detection and was found to have 100% sensitivity and specificity. In conclusion, the 18S TaqMan real-time PCR assay is a sensitive, specific, and rapid method for identification of B. microti among cases of babesiosis in the United States.