How should I diagnose acute sinusitis?
Acute sinusitis usually follows a common cold, and is defined as an increase in symptoms after 5 days, or persistence of symptoms beyond 10 days, but less than 12 weeks.

In adults:
Diagnose acute sinusitis by the presence of nasal blockage (obstruction/congestion) or discoloured nasal discharge (anterior/posterior nasal drip) with facial pain/pressure (or headache) and/or reduction (or loss) of the sense of smell.

Nasal blockage — usually bilateral and caused by rhinitis.
Facial pain/pressure — may be localized over the infected sinus, or it may affect teeth, the upper jaw, or other areas (such as the eye, side of face, forehead). Pain in the absence of other symptoms is unlikely to be sinusitis.

In children:
Diagnose acute sinusitis by the presence of nasal blockage (obstruction/congestion) or discoloured nasal discharge (anterior/posterior nasal drip) with facial pain/pressure (or headache) and/or cough (daytime and night-time).
Facial pain is less prevalent in children.
There may also be ear discomfort (Eustachian tube blockage).

Suspect acute bacterial sinusitis when at least three of the following features are present:

Discoloured or purulent discharge (with unilateral predominance).
Severe local pain (with unilateral predominance).
A fever greater than 38°C.
A marked deterioration after an initial milder form of the illness (so-called ‘double-sickening’).
Elevated ESR/CRP (although the practicality of this criterion is limited).

Examination:
Inspect and palpate the maxillofacial area to elicit swelling and tenderness.
Perform anterior rhinoscopy (using the largest speculum of an otoscope, or a head light and nasal speculum) to identify:
Signs which support a diagnosis of acute sinusitis such as nasal inflammation, mucosal oedema, and mucopurulent nasal discharge.
Associated pathology such as nasal polyps, or anatomical abnormalities such as septal deviation.
Polyps can be distinguished from the inferior turbinate by their lack of sensitivity to painful stimuli, their yellow-grey colour, and the fact that they can be compressed with a cotton wool bud. Usually, only significant polyposis is detectable in primary care.

Evidence of other conditions which present with similar signs and symptoms to acute sinusitis, such as a nasal foreign body or a sinonasal tumour.
If signs and symptoms are not typical of sinusitis, rule out an alternative diagnosis.

Differential diagnosis
Other conditions presenting with similar signs and symptoms to acute sinusitis include:
Allergic rhinitis — usually restricted to nasal symptoms. Consider this especially if symptoms have not directly followed an upper respiratory tract infection or are persistent.

Nasal foreign body — typically causes a unilateral mucopurulent discharge or blockage (more common in children).

Adenoiditis and tonsillitis (particularly in children) — causes nasal blockage, breathing through the mouth, nasal speech, and snoring.

Sinonasal tumour — suspect particularly if there are persistent unilateral symptoms, such as bloodstained discharge, crusting, nasal obstruction, non-tender facial pain, facial swelling, or unilateral nasal polyps. Refer urgently to an Ear, Nose, and Throat (ENT) specialist.

Other causes of facial pain or headache include:

Tension-type headache may present with bilateral symptoms of pressure but with no other nasal symptoms.
Temporomandibular joint dysfunction, or habitual teeth clenching.
Neuropathic or atypical facial pain.
Dental pain (typically, pain made worse by hot and cold drinks, or by chewing).

Management to follow.

G Mohan.