Detection and Monitoring of SARS Coronavirus in the Plasma and Peripheral Blood Lymphocytes of Patients with Severe Acute Respiratory Syndrome

Severe acute respiratory syndrome (SARS) is a newly emerged infectious disease, and a novel SARS-associated coronavirus (CoV) has been identified as a causative agent (1)(2)(3). Reliable and sensitive determination of the SARS CoV load would aid in the early identification of infected individuals, provide guidance for treatment (especially the use of steroid hormones and antiviral agents), and aid in monitoring of a patient’s clinical course and outcome.Among the available tests, viral gene amplification by reverse transcription-PCR (RT-PCR) provides a relatively rapid and specific test for the diagnosis of individuals showing SARS-associated symptoms (4)(5). RT-PCR was successfully used to detect SARS CoV in nasopharyngeal aspirates, nasopharyngeal swabs, throat swabs, and broncheoalveolar lavage of SARS patients (6)(7). However, because the composition of these samples varies with time and among individuals, they are unlikely to serve as a standardized sample source for quantification, comparison, or monitoring of SARS CoV infection. To meet clinical needs, some improved RT-PCR methods have been developed, and plasma has been used as a sample source (8)(9)(10). The consistency of plasma composition makes it a good sample source for monitoring the CoV load.CoV-enriched samples are critical for achieving a high detection rate. Current methods have a limited detection window, largely because they do not fully utilize the CoV viral RNA in the sample. Because of its high false-negative rate, the current method is unable to definitively rule out SARS within days after onset (11). An increase in viral RNA input could enhance the chance of detecting CoV (12).The input to PCR can be increased by reducing the loss of CoV during sample preparation (8)(12) or by increasing the amount of prepared CoV RNA and cDNA product used in the final PCR …