Diagnostic tests
1st test to order
Test Result
pulse oximetry
• Order in patients with severe illness.
• Recommended in patients with respiratory distress and cyanosis.
may show low oxygen
saturation (SpO₂ <90%)
ABG
• 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%).
may show low partial
oxygen pressure
FBC
• 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.[4] [5] [6]
leukopenia; lymphopenia;
leukocytosis
coagulation screen
• Order in patients with severe illness.
• The most common abnormalities are elevated D-dimer and prolonged
prothrombin time.[4] [5] [6]
• Non-survivors had significantly higher D-dimer levels and longer
prothrombin time and activated partial thromboplastin time compared
with survivors in one study.[64]
elevated D-dimer;
prolonged prothrombin
time
comprehensive metabolic panel
• 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.[4] [5]
elevated liver
transaminases;
decreased albumin; renal
impairment
serum procalcitonin
• Order in patients with severe illness.
• May be elevated in patients with secondary bacterial infection.[4] [5]
may be elevated
serum C-reactive protein
• Order in patients with severe illness.
• May be elevated in patients with secondary bacterial infection.[4] [5]
may be elevated
serum lactate dehydrogenase
• Order in patients with severe illness.
• Elevated lactate dehydrogenase has been reported in 73% to 76% of
patients.[4] [5]
• Indicates liver injury or lysis of blood erythrocytes.
may be elevated
serum creatine kinase
• Order in patients with severe illness.
• Elevated creatine kinase has been reported in 13% to 33% of
patients.[4] [5]
• Indicates muscle or myocardium injury.
may be elevated
serum troponin level may be elevated
• Order in patients with severe illness.
• May be elevated in patients with cardiac injury.[4]
blood and sputum cultures
• Collect blood and sputum specimens for culture in all patients to
rule out other causes of lower respiratory tract infection, especially
patients with an atypical epidemiological history.
• Specimens should be collected prior to starting empirical
antimicrobials if possible.
negative for bacterial
infection
real-time reverse transcription polymerase chain reaction (RTPCR)
• Molecular testing is required to confirm the diagnosis.[54]
• Collect lower respiratory tract specimens (sputum, endotracheal
aspirate, bronchoalveolar lavage) where possible and depending
upon the patient’s condition.
• Upper respiratory tract specimens (nasopharyngeal aspirate or
combined nasopharyngeal and oropharyngeal swabs) may be used if
lower respiratory tract specimens cannot be collected.
• If initial testing is negative in a patient who is strongly suspected to
have COVID-19, recollect specimens from multiple respiratory tract
sites (nose, sputum, endotracheal aspirate) and retest.
• Blood, urine, and stool specimens may also be used to monitor for
the presence of the virus.
• The US Food and Drug Administration has issued an emergency-use
authorisation to enable emergency use of the US Center for Disease
Control and Prevention (CDC)’s RT-PCR diagnostic panel, which
allows testing at any CDC-qualified laboratory in the US.[65] This test
is also available in many laboratories worldwide and testing should be
done according to instructions from local health authorities.
• Collect nasopharyngeal swabs to rule out influenza and other
respiratory infections.
positive for severe acute
respiratory syndrome
coronavirus 2 (SARSCoV-2) viral RNA; negative
for influenza A and
B viruses and other
respiratory pathogens
chest x-ray
• 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