Development and Clinical Validation of a Multiplex Real-Time Quantitative PCR Assay for Human Infection by Anaplasma phagocytophilum and Ehrlichia chaffeensis

Background: Human granulocytic anaplasmosis (HGA), caused by Anaplasma phagocytophilum, and human monocytic ehrlichiosis (HME), caused by Ehrlichia chaffeensis, often present as undifferentiated fever but are not treated by typical empiric regimens for acute febrile illness. Their role as agents of vector-borne febrile disease in tropical regions is more poorly studied than for other rickettsial infections. Limitations in diagnosis have impaired epidemiologic and clinical research and needless morbidity and mortality occur due to untreated illness. Methods: We designed and clinically validated a multiplex real-time quantitative PCR assay for Anaplasma phagocytophilum and Ehrlichia chaffeensis using samples confirmed by multiple gold-standard methods. Results: Clinical sensitivity and specificity for A. phagocytophilum were 100% (39/39) and 100% (143/143), respectively, and for E. chaffeensis 95% (20/21) and 99% (159/161), respectively. Conclusions: These assays could support early diagnosis and treatment as well as the high-throughput testing required for large epidemiologic studies.