Investigations

1st investigations to order

Test
Result
Test

Leukopenia is common, with lymphopenia reported in 98% of patients early in the disease.[3] Lymphopenia is due to reduced CD4 and CD8 cell counts. Thrombocytopenia is found in the presence of DIC.

Result

leukopenia, lymphopenia with reduced CD4 and CD8 cell counts, thrombocytopenia

Test
Result
Test

Mild elevation of AST and ALT has been reported in 23% to 50% of SARS patients, although this result shows low specificity for diagnosis of the disease.[19]

Result

elevated AST and ALT

Test
Result
Test

Common, nonspecific laboratory abnormality. Indicates liver injury or lysis of blood erythrocytes.

Result

elevated

Test
Result
Test

Common, nonspecific laboratory abnormality. Indicates muscle or myocardium injury. Has also been related to left ventricular dysfunction.[4]

Result

elevated

Test
Result
Test

All patients with signs of severe infection should receive blood and sputum cultures to rule out other causes of a lower respiratory tract infection, especially those without a typical epidemiologic history for SARS.

Result

negative for bacterial infection

Test
Result
Test

All patients with signs of severe infection should receive blood and sputum cultures to rule out other causes of a lower respiratory tract infection, such as community-acquired pneumonia, especially those without a typical epidemiologic history for SARS.

Result

negative for Streptococcus pneumoniae or other infecting bacteria

Test
Result
Test

To rule out presence of influenza infection.

Result

negative for influenza A and influenza B viruses

Test
Result
Test

To rule out presence of influenza infection.

Result

negative for influenza A and influenza B viruses

Test
Result
Test

About 20% to 25% of cases have a normal chest x-ray on presentation.[24][25]

Examine chest x-ray for unilateral or bilateral infiltrates in the peripheries of the lower zones. Infiltrates manifest as patchy, confluent, or diffuse consolidation, or nodular shadowing. com.bmj.content.model.Caption@2b097f37[Figure caption and citation for the preceding image starts]: CXR of a SARS patient showing multifocal opacitiesKetai L, et al. J Thorac Imaging. 2006;21:276-283; used with permission [Citation ends].

Cavitation, hilar lymphadenopathy, and pleural effusion are not typically seen.[26]

Pneumomediastinum and pneumothorax often occur with assisted ventilation.[27]

Result

unilateral or bilateral infiltrates

Test
Result
Test

Indicated in patients with respiratory distress and cyanosis.

Result

low oxygen saturation (SpO2 <90%)

Test
Result
Test

For a positive diagnosis based on PCR testing, the patient must have either 2 positive clinical specimens from different anatomic sites or positive specimens from the same site on 2 separate occasions.[40]

Multiple specimen sources should be sampled: nasopharyngeal, oropharyngeal, and serum/plasma specimens (during first week); nasopharyngeal, oropharyngeal, and stool specimens (after first week).

Preferred samples are a nasopharyngeal aspirate (often negative in first week of infection) or throat swab obtained in viral transport media. Dacron or rayon swabs with plastic shafts should be used rather than those with calcium alginate or wooden sticks. Specimens must be shipped in cold packs to keep the sample at 39.2°F (4°C).

Stool specimens or whole blood samples in ethylene diamine tetra-acetic acid (EDTA) are also appropriate.

Quantitative measurement of blood SARS coronavirus (CoV) RNA with the technique of real time RT-PCR has a detection rate of 80% as early as day 1 of the disease.[32]

Result

positive for SARS coronavirus (CoV)-specific RNA

Investigations to consider

Test
Result
Test

Performed when the SpO2 measured with pulse oximetry is <90%.

Result

low partial oxygen pressure

Test
Result
Test

Indicated in patients with spontaneous bleeding.

Result

prolonged PT, elevated D-dimers

Test
Result
Test

Imaging of the thorax with HRCT should be undertaken in those with a normal chest x-ray on presentation and a high suspicion of SARS for the detection of lung opacities.

Abnormal in 67% of patients with an initially normal chest x-ray.[28]

Result

ground glass opacities with interlobular septal thickening ± subpleural consolidation

Test
Result
Test

Tested using an immunofluorescent antibody assay (IFA) or ELISA.

Useful for epidemiologic surveillance and retrospective diagnosis.

Serum specimens should be collected when the diagnosis is first suspected and at later times if indicated.

Seroconversion usually occurs 1 to 4 weeks (>90% after day 28) after the onset of symptoms, with an antibody response (4-fold increase in SARS-CoV antibody) occasionally detected during the first week of illness, likely to be detected by the end of the second week of illness, but not normally detected until >28 days into the illness.[40][33]

Result

4-fold increase in SARS-CoV antibody

Test
Result
Test

Not recommended for routine detection.[40]

Lacks sensitivity of RT-PCR.

Given the potential risk of transmission, growth of the SARS coronavirus (CoV) should be restricted to biosafety level III (or IV) laboratories.[33]

Result

growth of SARS coronavirus (CoV)

Emerging tests

Test
Result
Test

The key feature of this simple immunoswab diagnostic assay is its ability to detect the presence of the SARS-CoV antigen (nucleocapsid protein) within 45 to 60 minutes following availability of the body fluid samples.[34]

Result

detects presence of SARS-CoV antigen

Test
Result
Test

Five monoclonal antibodies against recombinant nucleocapsid protein of SARS coronavirus (CoV) were developed by hybridoma technology. Potentially ideal candidates for developing early and sensitive diagnostic assays for SARS-CoV.[35]

Result

detects presence of SARS coronavirus (CoV) with high specificity

Use of this content is subject to our disclaimer