Investigations

1st investigations to order

Test
Result
Test

Order in patients with severe illness.

Recommended in patients with respiratory distress and cyanosis.

Result

may show low oxygen saturation (SpO₂ <90%)

Test
Result
Test

Order in patients with severe illness as indicated to detect hypercarbia or acidosis.

Recommended in patients with respiratory distress and cyanosis who have low oxygen saturation (SpO₂ <90%).

Result

may show low partial oxygen pressure

Test
Result
Test

Order in patients with severe illness.

The most common laboratory abnormalities in patients hospitalised with pneumonia include leukopenia, lymphopenia, and leukocytosis. Other abnormalities include neutrophilia, thrombocytopenia, and decreased haemoglobin.[20][21][37][122]

Thrombocytopenia has been associated with increased risk of severe disease and mortality and may be useful as a clinical indicator for monitoring disease progression.[145]

Result

leukopenia; lymphopenia; leukocytosis

Test
Result
Test

Order in patients with severe illness.

The most common abnormalities are elevated D-dimer and prolonged prothrombin time.[20][21][37]

Non-survivors had significantly higher D-dimer levels and longer prothrombin time and activated partial thromboplastin time compared with survivors in one study.[146]

Result

elevated D-dimer; prolonged prothrombin time

Test
Result
Test

Order in patients with severe illness.

The most common laboratory abnormalities in patients hospitalised with pneumonia include elevated liver transaminases. Other abnormalities include decreased albumin and renal impairment.[20][21]

Liver function abnormalities may be more common in patients with COVID-19 compared with other types of pneumonia.[132]

Result

elevated liver transaminases; decreased albumin; renal impairment

Test
Result
Test

Order in patients with severe illness.

May be elevated in patients with secondary bacterial infection.[20][21] May be more common in children.[121]

Result

may be elevated

Test
Result
Test

Order in patients with severe illness.

May be elevated in patients with secondary bacterial infection.[20][21]

Result

may be elevated

Test
Result
Test

Order in patients with severe illness.

Elevated lactate dehydrogenase has been reported in 73% to 76% of patients.[20][21] May be more common in patients with COVID-19 compared with other types of pneumonia.[132]

Indicates liver injury or lysis of blood erythrocytes.

Result

may be elevated

Test
Result
Test

Order in patients with severe illness.

Elevated creatine kinase has been reported in 13% to 33% of patients.[20][21]

Indicates muscle or myocardium injury.

Result

may be elevated

Test
Result
Test

Order in patients with severe illness.

May be elevated in patients with cardiac injury.[20]

Result

may be elevated

Test
Result
Test

Collect blood and sputum specimens for culture in all patients to rule out other causes of lower respiratory tract infection and sepsis, especially patients with an atypical epidemiological history.[5]

Specimens should be collected prior to starting empirical antimicrobials if possible.

Result

negative for bacterial infection

Test
Result
Test

Molecular testing is required to confirm the diagnosis. Nucleic acid sequencing may be required to confirm the diagnosis.[123] Priorities for testing depend on local guidelines and available resources.

Collect upper respiratory specimens (nasopharyngeal and oropharyngeal swab or wash) in ambulatory patients and/or lower respiratory specimens (sputum and/or endotracheal aspirate or bronchoalveolar lavage) in patients with more severe respiratory disease. Also consider collecting additional clinical specimens (e.g., blood, stool, urine). Specimens should be collected under appropriate infection prevention and control procedures. Consider the high risk of aerolisation when collecting lower respiratory specimens.[123]

If a negative result is obtained from a patient with a high index of suspicion for COVID-19, additional specimens should be collected and tested, especially if only upper respiratory tract specimens were collected initially.[123]

Many tests are available under the US Food and Drug Administration’s emergency-use authorisation scheme.[147] A point-of-care test that provides results within hours has been approved and will be available soon.[148] Tests are available in many laboratories worldwide and testing should be done according to instructions from local health authorities and adhere to appropriate biosafety practices. If testing is not available nationally, specimens should be shipped to an appropriate reference laboratory.

Collect nasopharyngeal swabs to rule out influenza and other respiratory infections according to local guidance. It is important to note that co-infections can occur, and a positive test for a non-COVID-19 pathogen does not rule out COVID-19.[5][125]

Result

positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral RNA; may be positive for influenza A and B viruses and other respiratory pathogens

Test
Result
Test

Order in all patients with suspected pneumonia.

Unilateral lung infiltrates are found in 25% of patients, and bilateral lung infiltrates are found in 75% of patients.[20][21][128]

Result

unilateral or bilateral lung infiltrates

Test
Result
Test

Consider a CT scan of the chest. Abnormal chest CT findings have been reported in up to 97% of patients in one meta-analysis of 50,466 hospitalised patients.[109] CT is the primary imaging modality in China.[129]

CT imaging generally shows bilateral multiple lobular and subsegmental areas of ground-glass opacity or consolidation in most patients, usually with a peripheral or posterior distribution, mainly in the lower lobes and less frequently in the right lower lobe. Consolidative opacities superimposed on ground-glass opacity may be found in a smaller number of cases, usually older patients. Other atypical features include interlobular or septal thickening (smooth or irregular), thickening of the adjacent pleura, subpleural involvement, crazy paving pattern, and air bronchograms. Some patients may rarely present with pleural effusion, pericardial effusion, bronchiectasis, cavitation, pneumothorax, lymphadenopathy, and round cystic changes. Atypical features appear to be more common in the later stages of disease, or on disease progression. None of these findings appear to be specific or diagnostic for COVID-19.[20][111][130] Abnormalities can rapidly evolve from focal unilateral to diffuse bilateral ground-glass opacities that progress to, or co-exist with, consolidations within 1 to 3 weeks.[131] The greatest severity of CT findings is usually visible around day 10 after symptom onset, and imaging signs associated with clinical improvement (e.g., resolution of consolidative opacities, reduction in number of lesions and involved lobes) usually occur after week 2 of the disease.[130] A small comparative study found that patients with COVID-19 are more likely to have bilateral involvement with multiple mottling and ground-glass opacity compared with other types of pneumonia.[132]

Small nodular ground-glass opacities are the most common finding in children.[133] Consolidation with surrounding halo signs is a typical finding in children.[121]

Evidence of viral pneumonia on CT may precede a positive RT-PCR result for SARS-CoV-2 in some patients.[126] However, CT imaging abnormalities may be present in minimally symptomatic or asymptomatic patients.[47][131]

In a cohort of over 1000 patients in a hyperendemic area in China, chest CT had a higher sensitivity for diagnosis of COVID-19 compared with initial RT-PCR from swab samples (88% versus 59%). Improvement of abnormal CT findings also preceded change from RT-PCR positivity to negativity in this cohort during recovery. The sensitivity of chest CT was 97% in patients who ultimately had positive RT-PCR results. However, in this setting, 75% of patients with negative RT-PCR results also had positive chest CT findings. Of these patients, 48% were considered highly likely cases, while 33% were considered probable cases.[135]com.bmj.content.model.Caption@2100c59e[Figure caption and citation for the preceding image starts]: Transverse CT scans from a 32-year-old man, showing ground-glass opacity and consolidation of lower lobe of right lung near the pleura on day 1 after symptom onset (top panel), and bilateral ground-glass opacity and consolidation on day 7 after symptom onsetXu XW et al. BMJ. 2020;368:m606 [Citation ends].

Result

bilateral ground-glass opacity or consolidation

Emerging tests

Test
Result
Test

Serological testing is not available as yet, but assays are in development.[126] Serum samples can be stored to retrospectively define cases when validated serology tests become available.

Early data indicate continuous high levels of IgM during the acute phase of infection, with IgM lasting more than 1 month (indicating prolonged virus replication in infected patients). IgG responded later than IgM.[127]

Result

positive for SARS-CoV-2 virus antibodies

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