RT Journal Article
SR Electronic
T1 Interpretation of diagnostic laboratory tests for severe acute respiratory syndrome: the Toronto experience
JF Canadian Medical Association Journal
JO CMAJ
FD Canadian Medical Association
SP 47
OP 54
VO 170
IS 1
A1 Patrick Tang
A1 Marie Louie
A1 Susan E. Richardson
A1 Marek Smieja
A1 Andrew E. Simor
A1 Frances Jamieson
A1 Margaret Fearon
A1 Susan M. Poutanen
A1 Tony Mazzulli
A1 Raymond Tellier
A1 James Mahony
A1 Mark Loeb
A1 Astrid Petrich
A1 Max Chernesky
A1 Allison McGeer
A1 Donald E. Low
A1 Elizabeth Phillips
A1 Steven Jones
A1 Nathalie Bastien
A1 Yan Li
A1 Daryl Dick
A1 Allen Grolla
A1 Lisa Fernando
A1 Timothy F. Booth
A1 Bonnie Henry
A1 Anita R. Rachlis
A1 Larissa M. Matukas
A1 David B. Rose
A1 Reena Lovinsky
A1 Sharon Walmsley
A1 Wayne L. Gold
A1 Sigmund Krajden
A1 the Ontario Laboratory Working Group for the Rapid Diagnosis of Emerging Infections
YR 2004
UL http://www.cmaj.ca/content/170/1/47.abstract
AB Background: An outbreak of severe acute respiratory syndrome (SARS) began in Canada in February 2003. The initial diagnosis of SARS was based on clinical and epidemiological criteria. During the outbreak, molecular and serologic tests for the SARS-associated coronavirus (SARS-CoV) became available. However, without a “gold standard,” it was impossible to determine the usefulness of these tests. We describe how these tests were used during the first phase of the SARS outbreak in Toronto and offer some recommendations that may be useful if SARS returns. Methods: We examined the results of all diagnostic laboratory tests used in 117 patients admitted to hospitals in Toronto who met the Health Canada criteria for suspect or probable SARS. Focusing on tests for SARS-CoV, we attempted to determine the optimal specimen types and timing of specimen collection. Results: Diagnostic test results for SARS-CoV were available for 110 of the 117 patients. SARS-CoV was detected by means of reverse-transcriptase polymerase chain reaction (RT-PCR) in at least one specimen in 59 (54.1%) of 109 patients. Serologic test results of convalescent samples were positive in 50 (96.2%) of 52 patients for whom paired serum samples were collected during the acute and convalescent phases of the illness. Of the 110 patients, 78 (70.9%) had specimens that tested positive by means of RT-PCR, serologic testing or both methods. The proportion of RT-PCR test results that were positive was similar between patients who met the criteria for suspect SARS (50.8%, 95% confidence interval [CI] 38.4%–63.2%) and those who met the criteria for probable SARS (58.0%, 95% CI 44.2%–70.7%). SARS-CoV was detected in nasopharyngeal swabs in 33 (32.4%) of 102 patients, in stool specimens in 19 (63.3%) of 30 patients, and in specimens from the lower respiratory tract in 10 (58.8%) of 17 patients. Interpretation: These findings suggest that the rapid diagnostic tests in use at the time of the initial outbreak lack sufficient sensitivity to be used clinically to rule out SARS. As tests for SARS-CoV continue to be optimized, evaluation of the clinical presentation and elucidation of a contact history must remain the cornerstone of SARS diagnosis. In patients with SARS, specimens taken from the lower respiratory tract and stool samples test positive by means of RT-PCR more often than do samples taken from other areas.