The approach should include:
A history eliciting a constellation of symptoms compatible with the diagnosis
Identification of risk factors suggestive of the condition (for example, seasonal occurrence, smoking, exposure to affected individuals)
A brief physical examination, including temperature, examination of oropharynx, nares, neck, and chest; if the patient looks ill, consider influenza as a cause and add pulse and blood pressure to rule out septic shock from a bacterial cause (e.g., meningococcal septicaemia)
Excluding alternative diagnoses by screening for distinguishing features of conditions with overlapping symptoms, such as allergic rhinitis.
No laboratory tests are required in the initial stages.
Common symptoms include any or all of the following:
An alternative or underlying diagnoses should be considered if:
A sore throat is the main symptom (streptococcal pharyngitis or tonsillitis should be considered, especially if the patient is younger than 15 years of age). Use of the McIsaac score[ Sore Throat (Pharyngitis) Evaluation and Treatment Criteria (McIsaac) ] can be useful to differentiate from streptococcal infection
Rhinitis has been present for more than 14 days (e.g., allergic rhinitis)
The illness started suddenly with fever, chills, and severe muscle aches (e.g., influenza or pneumonia)
Pleuritic pain, large amounts of sputum, or blood in the sputum (e.g., pleurisy or pneumonia)
Otalgia (e.g., otitis media)
Facial pain (sinusitis)
Features of meningism are present (altered consciousness, photophobia, hypotonia, neck stiffness, seizures, and tachycardia).
In adults, an elevated temperature is unusual, but this is common in children. A temperature greater than 38°C (100.4°F) increases the likelihood of the diagnosis being influenza. Pulse and blood pressure should be measured to rule out septic shock from a bacterial cause (e.g., meningococcal septicaemia) in people who look moderately ill. Meningococcal septicaemia may mimic the common cold as both can present with fever and muscle aches; however, someone with meningococcal septicaemia is less likely to have respiratory symptoms, such as sore throat, sneezing, and rhinitis. They will likely have a fever, tachycardia and hypotension.
Examination of the oropharynx:
A typical viral infection will have non-specific erythematous inflammation of the pharynx. Purulent drainage in the posterior pharynx may be present. The presence of pus on the tonsils is suggestive of streptococcal infection and should be followed by an examination of the anterior cervical glands of the neck.
Erythema and oedema may be present. Purulent drainage in both nares is common.
Should be assessed as may indicate meningism. In infants, a bulging fontanelle and a characteristic high-pitched cry may occur. A positive Kernig's or Brudzinski's sign indicates meningeal inflammation and is suggestive of meningitis. This is present in a minority of patients.
For a diagnosis of the common cold, a clear chest is essential. If the patient has lower respiratory signs, other diagnoses should be considered, such as an acute exacerbation of asthma or COPD or pneumonia. In children, bronchiolitis and croup should be considered.
No laboratory tests are needed to confirm the diagnosis. Using a point-of-care test for C-reactive protein in primary care settings for patients who present with acute respiratory symptoms can reduce antibiotic use, but with no effect on patient-reported outcomes. There is no consensus on the place of point-of-care testing for the common cold.
At follow-up, where symptoms have persisted beyond normal disease duration or atypical features are present, laboratory investigations may be justified. Specific tests can confirm or exclude alternative diagnoses, such as a throat swab to exclude streptococcal pharyngitis or a chest x-ray to confirm pneumonia. The Monospot test should be ordered when there is clinical suspicion of infectious mononucleosis.
Rapid viral testing has not been shown to reduce antibiotic use; it has been shown to reduce the need for chest x-rays in the accident and emergency department but has not been demonstrated to have any other effects on other tests or waiting times. Viral testing has a place only as part of research or as a tool for the early diagnosis of influenza during a pandemic.
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