CMAJ • November 23, 2004; 171 (11). doi:10.1503/cmaj.1040398.
© 2004 Canadian Medical Association or its licensors
All editorial matter in CMAJ represents the opinions of the authors and not necessarily those of the Canadian Medical Association.
Chung-Ming Chu ,
Leo L.M. Poon ,
Vincent C.C. Cheng ,
Kin-Sang Chan ,
Ivan F.N. Hung ,
Maureen M.L. Wong ,
Kwok-Hung Chan ,
Wah-Shing Leung ,
Bone S.F. Tang ,
Veronica L. Chan ,
Woon-Leung Ng ,
Tiong-Chee Sim ,
Ping-Wing Ng ,
Kin-Ip Law ,
Doris M.W. Tse ,
Joseph S.M. Peiris and
Kwok-Yung Yuen
© 2004 Canadian Medical Association or its licensors
All editorial matter in CMAJ represents the opinions of the authors and not necessarily those of the Canadian Medical Association.
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Initial viral load and the outcomes of SARS
From the Department of Medicine and Geriatrics (Chu, K.S. Chan, Leung, V.L. Chan, W.L. Ng, Sim, P.W. Ng) and the Intensive Care Unit (Law), United Christian Hospital, Hong Kong Special Administrative Region, China; the Department of Microbiology, Queen Mary Hospital, The University of Hong Kong (Poon, Cheng, Hung, Tang, K.H. Chan, Peiris, Yuen), Hong Kong Special Administrative Region, China; and the Department of Medicine and Geriatrics, Caritas Medical Centre (Wong, Tse), Hong Kong Special Administrative Region, China
Background: Severe acute respiratory syndrome (SARS) is caused by a novel coronavirus. It may progress to respiratory failure, and a significant proportion of patients die. Preliminary data suggest that a high viral load of the SARS coronavirus is associated with adverse outcomes in the intensive care unit, but the relation of viral load to survival is unclear.
Methods: We prospectively studied an inception cohort of 133 patients with virologically confirmed SARS who were admitted to 2 general acute care hospitals in Hong Kong from Mar. 24 to May 4, 2003. The patients were followed until death or for a minimum of 90 days. We used Cox proportional hazard modelling to analyze potential predictors of survival recorded at the time of presentation, including viral load from nasopharyngeal specimens (measured by quantitative reverse transcriptase polymerase chain reaction [PCR] of the SARS-associated coronavirus).
Results: Thirty-two patients (24.1%) met the criteria for acute respiratory distress syndrome, and 24 patients (18.0%) died. The following baseline factors were independently associated with worse survival: older age (61–80 years) (adjusted hazard ratio [HR] 5.24, 95% confidence interval [CI] 2.03–13.53), presence of an active comorbid condition (adjusted HR 3.36, 95% CI 1.44–7.82) and higher initial viral load of SARS coronavirus, according to quantitative PCR of nasopharyngeal specimens (adjusted HR 1.21 per log10 increase in number of RNA copies per millilitre, 95% CI 1.06–1.39).
Interpretation: We found preliminary evidence that higher initial viral load is independently associated with worse prognosis in SARS. Mortality data for patients with SARS should be interpreted in light of age, comorbidity and viral load. These considerations will be important in future studies of SARS.
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