Serial Analysis of the Plasma Concentration of SARS Coronavirus RNA in Pediatric Patients with Severe Acute Respiratory Syndrome (Technical Briefs‪)‬

The recent identification of a novel coronavirus, SARS coronavirus (SARS-CoV), as an etiologic agent for severe acute respiratory syndrome (SARS) has prompted many groups to develop rapid and accurate molecular assays for the detection of this virus (1-4). To date, most of the assays have focused predominantly on samples taken from nasopharyngeal aspirates, urine, and stools (5, 6). Although detection of SARS-CoV RNA in the plasma of SARS patients has been reported (1), the relatively low sensitivity of the ultracentrifugation-based approach for detecting SARS-CoV RNA in plasma has made this assay impractical. Recently we showed that a one-step real-time quantitative reverse transcription-PCR (RT-PCR) assay for the polymerase region of the SARS-CoV genome could detect viral RNA in 75-78% of nonultracentrifuged serum samples from adult SARS patients during the early stage of disease and that the serum SARS-CoV concentrations on admission were of prognostic significance (7). This finding demonstrates that plasma/ serum SARS-CoV quantification may potentially be useful for the early diagnosis of SARS. Although most existing reports have focused on adult SARS patients, recent reports revealed that the clinical course was less severe in pediatric SARS patients than in adult SARS patients (8,9). On the whole, the outcomes of pediatric SARS patients have been favorable. In this study, we investigated whether SARS-CoV RNA can be detected in the plasma samples of pediatric patients during different stages of SARS and studied the serial variation in viral loads. We quantified SARS-CoV RNA by real-time RT-PCR in the plasma of eight pediatric patients admitted to the New Territories East Cluster of Hospital Authority Hospitals in Hong Kong and who satisfied the WHO surveillance case definition for SARS (9). These patients were recruited between March 13, 2003, and May 17, 2003. Informed consent was obtained from the patients or their parents, and ethics approval was obtained from the Institutional Review Board. The serial blood samples used in this study were collected from the patients during sample collection for routine blood tests for monitoring lymphocyte counts and biochemical indices and enzymes. The convalescent sera of these patients were tested for IgG antibody against SARS-CoV with SARS-CoV-infected cells in an indirect immunofluorescence assay (6). All patients were serologically positive for SARS-CoV IgG antibody. As negative controls, blood samples from 15 pediatric patients who suffered from fever and infections other than SARS were collected. The plasma SARS-CoV RNA concentrations in the pediatric patients were compared with the results for adult SARS patients as reported previously (7).