Diagnosis & Reporting
Case Definition & Reporting
(22/4/2003)
Clinical Features (15/4/2003) Radiological Diagnosis
(15/4/2003)
Admission Criteria
(7/4/2003)
Diagnostic Test (15/5/2003)

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A. CASE DEFINITION & REPORTING PROCEDURES (22/4/2003)


Case Definition 


Criteria for reporting to HA SARS Registry: (22/04/2003)

1.  Radiographic evidence of infiltrates consistent with pneumonia, and
2. Fever >38°C or history of such at any time in the past 2 days, and
3.  At least 2 of the following:
a)  History of chills in the past 2 days
b)  Cough (new or increased cough) or breathing difficulty
c)  General malaise or myalgia
d)  Known history of exposure

Exclusion criteria
A case should be excluded if an alternative diagnosis can fully explain their illness.

Suspected cases
Does not completely fulfil the above definition but still considered to be highly likely of SARS on clinical judgment.

The status of a reported case may change over time and a patient should always be managed as clinically appropriate, regardless of their case status.

 

 

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B. CLINICAL FEATURES (15/4/2003)
 
  Chinese University of Hong Kong¹ University of Hong Kong² Canadian SARS Study Team³
Patient population 66 males, 72 females
69 HCWs
Mean age 39.3±16.8 years
5 males, 5 females
Mean age 52.5 ± 11.0 years
6 males, 4 female
Age: 24-78 years
Clinical presentations Fever (100%)
Chills ± rigors (73.2%)
Myalgia (60.9%)
Cough (57.3%)
Headache (55.8%)
Dizziness (42.8%)
Sputum production (29.0%)
Sore throat (23.2%)
Coryza (22.5%)
Nausea & vomiting (19.6%)
Diarrhoea (19.6%)
Fever (100%)
Rigor (90%)
Cough (80%)
Headache (70%)
Malaise (70%)
Dyspnoea (60%)
Myalgia (50%)
Pleurisy (30%)
Sputum production (10%)
Fever (100%)
Nonproductive cough (100%)
Dyspnoea (80%)
Malaise (70%)
Diarrhea (50%)
Chest pain (30%)
Headache (30%)
Sore throat (30%)
Myalgias (20%)
Vomiting (10%)
Laboratory findings Lymphopenia (69.6%)
Thrombocytopenia (44.8%)
Prolonged APTT (42.8%)
↑ D-dimer (45.0%)
↑ ALT (23.4%)
↑ LDH (71.0%)
↑ CK (32.1%)
Hyponatremia (20.3%)
Hypokalemia (25.2%)
Lymphopenia (90%)
↑ALT
Oxygen saturation on room air <95% (78%)
Leukopenia (22%)
Lymphopenia (89%)
Thrombocytopenia (33%)
↑ALT (56%)
↑AST (78%%)
↑LDH (80%)
↑CK (56%)
Chest X-ray findings At the onset of fever, 78.3% had abnormal CXR (air-space consolidation)
54.6% unilateral focal involvement
45.4% either unilateral multifocal or bilateral involvement
Progressive air-space disease Infiltrate on CXR (100%)
Incubation period 2-16 days (median 6 days) 2-11 days 3-10 days
Admission to ICU 32 patients (23.2%)    
Mechanical ventilation 19 patients (13.8%) 2 patients (20%) 5 patients (50%)
Mortality rate 5 patients (3.6%) 2 patients (20%) 3 patients (30%)
Independent predictors of adverse outcome Advanced age (OR 1.8)
High peak LDH (OR 2.09)
High absolute neutrophil count on presentation (OR 1.6)
   
1. Nelson Lee et al. A Major Outbreak of Severe Acute Respiratory Syndrome in Hong Kong. NEJM online April 7, 2003.
2. Kenneth W Tsang et al. A Cluster of Cases of Severe Acute Respiratory Syndrome in Hong Kong. NEJM online March 31, 2003.
3. Susan M Poutanen et al. Identification of Severe Acute Respiratory Syndrome in Canada. NEJM online March 31, 2003.

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C. RADIOLOGICAL DIAGNOSIS (15/4/2003)

To facilitate early radiological diagnosis and management, the various radiological / CT appearances of SARS together with a recommended imaging protocol prepared by the Department of Diagnostic Radiology and Organ Imaging, CUHK & PWH are accessible on the website: http://www.droid.cuhk.edu.hk/web/atypical_pneumonia/atypical_pneumonia.htm

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D. ADMISSION CRITERIA (7/4/2003)

Two clinical pathways (depicted by the charts below) are designed for patients with and without definite contacts with regard to when and where to admit  them.

Chart 1      AED Flowchart for patients with definite contact with Severe Acute Respiratory Syndrome patients (within 10 days) (please click to view chart).
Chart 2    AED Flowchart for patients with no definite contact with Severe Acute Respiratory Syndrome patients (please click to view chart).

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E. Diagnostic test (15/5/2003)

 

1. The ensuing paragraphs (para 2 – 11) on laboratory diagnostic tests are extracted from the World Health Orgainisation SARS webpage (29 April 03):
 
a) Until standardized reagents for virus and antibodies detection are available and methods have been adequately field tested, SARS diagnosis remains based on the clinical and epidemiological findings.
b) Laboratory test result criteria for confirming or rejecting the diagnosis of SARS remain to be defined.
   

 

Molecular tests

 

2. Polymerase chain reaction (PCR) can detect genetic material of the SARS-CoV in various specimens (blood, stool, respiratory secretions or body tissues).
   
3. Principally, existing PCR tests are very specific but lack sensitivity. This means that negative tests cannot rule out the presence of the SARS virus in patients. Furthermore, contamination of samples in laboratories in the absence of laboratory quality control can lead to false positive results.
   
4. Positive PCR results, with the necessary quality control procedures in place. Recommendations for laboratories testing for SARS-coronavirus , are very specific and mean that there is genetic material (RNA) of the SARS-CoV in the sample. This does not mean that there is live virus present, or that it is present in a quantity large enough to infect another person.
   
5. Negative PCR results do not exclude SARS. SARS-CoV PCR can be negative for the following reasons:
 
  • The patient is not infected with the SARS coronavirus; the illness is due to another infectious agent (virus, bacterium, fungus) or a non-infectious cause.

  • The test results are incorrect (“false-negative”). Current tests need to be further developed to improve sensitivity.

  • Specimens were not collected at a time when the virus or its genetic material was present. The virus and its genetic material may be present for a brief period only, depending on the type of specimen tested.

 

Antibody tests

 

6. These tests detect antibodies produced in response to the SARS coronavirus infection. Different types of antibodies (IgM and IgG) appear and change in level during the course of infection. They can be undetectable at the early stage of infection. IgG usually remains detectable after resolution of the illness. The following test formats are being developed:
   
 
  • ELISA (Enzyme Linked ImmunoSorbant Assay): a test detecting a mixture of IgM and IgG antibodies in the serum of SARS patients yields positive results reliably at around day 21 after the onset of illness.
  • IFA (Immunofluorescence Assay): a test detecting IgM antibodies in serum of SARS patients yields positive results after about day 10 of illness. This test format is also used to test for IgG. This is a reliable test requiring the use of fixed SARS virus on an immunofluorescence microscope.
7. Positive antibody test results indicate a previous infection with SARS-CoV. Seroconversion from negative to positive or a four-fold rise in antibody titre from acute to convalescent serum indicates recent infection.
   
8. Negative antibody test results: No detection of antibody after 21 days from onset of illness seems to indicate that no infection with SARS-CoV took place.
   

 

Cell culture

 

9. Virus in specimens (such as respiratory secretions, blood or stool) from SARS patients can also be detected by inoculating cell cultures and growing the virus. Once isolated, the virus must be identified as the SARS virus with further tests. Cell culture is a very demanding test, but currently (with the exception of animal trials) only means to show the existence of a live virus.
   
10. Positive cell culture results indicate the presence of live SARS-CoV in the sample tested.
   
11. Negative cell culture results do not exclude SARS (see negative PCR test result).


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Disclaimer: This set of information is produced by the Hospital Authority to update our staff on issues relating to severe acute respiratory syndrome (SARS). They are listed under the topics above and will be updated as new information becomes available. Users should realise that SARS is a new disease and knowledge on its etiology, pathologenesis and treatment is limited and continuously evolving. Recommendations contained in this webpage are derived from consensus and must be regarded as provisional.