CDC adds lab criteria to SARS case definition for surveillance

Apr 30, 2003 (CIDRAP News) – Federal health officials have revised their surveillance case definition for SARS (severe acute respiratory syndrome) to include laboratory findings, but the revised definition should be used only for reporting, not clinical management, officials say.

The revision defines laboratory confirmation of a case as either detection of antibody to the SARS coronavirus (SARS Co-V), detection of the virus by two reverse transcriptase–polymerase chain reaction tests, or isolation of the virus in culture. A case is considered laboratory-negative only if serum obtained more than 21 days after illness onset tests negative for antibody to the virus.

The Centers for Disease Control and Prevention (CDC) presented the revised definition in a supplement to Morbidity and Mortality Weekly Report, issued yesterday.

The report states, "Reported US cases of SARS still will be classified as suspect or probable; however, these cases can be further classified as laboratory-confirmed or laboratory-negative if laboratory data are available and complete, or as laboratory-indeterminate if specimens are not available or testing is incomplete. Obtaining convalescent serum samples to make a final determination about infection with SARS Co-V is critical."

The CDC also states, "This surveillance case definition should be used for reporting and classification purposes only. It should not be used for clinical management or as the only criterion for identifying or testing patients who might have SARS or for instituting infection-control precautions."

The revised definition also includes clinical and epidemiologic criteria for SARS. Cases are classified as "suspect" if they include a temperature greater than 100.4ºF with signs and symptoms of moderate respiratory illness (eg, cough, shortness of breath, difficulty breathing, or hypoxia). Probable cases are those that also involve either radiographic evidence of pneumonia or respiratory distress syndrome.

CDC Director Julie Gerberding told a Senate committee yesterday that the CDC will send SARS test kits to state health departments by the end of this week.

CDC. Updated interim surveillance case definition for severe acute respiratory syndrome (SARS)—United States, April 29, 2003. MMWR Dispatch;52(Apr 29,2003)

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