What findings distinguish acute bacterial sinusitis?

Evidence summary

In one series, 87% of patients with the common cold had an abnormal computed tomography (CT) scan of the sinuses 48 to 96 hours after onset. Abnormalities visible on the CT scan persisted in 20% of patients at 2 weeks, yet epidemiological studies have shown that acute bacterial rhinosinusitis develops in only 0.5% to 2% of upper respiratory infections in adults. In primary care, only half of patients with a clinical diagnosis of acute bacterial rhinosinusitis have it proven upon aspiration.⁵

Two studies compared clinical findings with sinus puncture, the reference standard for acute bacterial rhinosinusitis. Berg found 4 independent predictors of aspirate purulence in Swedish emergency room patients with “paranasal” symptoms lasting <3 months (Table).¹ Together, unilateral purulent nasal discharge and predominantly unilateral pain predicated purulence on aspiration (sensitivity 79%, specificity 83%, positive predictive value [PPV], 80%). Clinical exam by an otolaryngologist had a PPV of 72%.

While emergency and primary care patients may differ, this study’s rate of aspiration-proven sinusitis (43%) is closer to that seen in primary care (50%) than in referral practices (70%–80%). This study’s limitations included unclear referral criteria, overlapping clinical predictors, and lack of culture data.

In a study of general practice patients in the United Kingdom with clinically diagnosed acute maxillary sinusitis, no signs or symptoms were independently associated with their illness.⁶ The authors concluded that the clinical examination was more or less worthless. Only patients with positive findings on CT scan underwent aspiration in this study. Less differentiated, less severe symptoms and a less stringent definition of positive aspiration in this study may account for the different results. Additionally, one third of patients eligible for this study refused participation or withdrew prior to sinus puncture.⁶

Other primary care studies used less accurate reference tests such as CT² (sensitivity and specificity unknown),⁵ x-ray³ (sensitivity 41%–90%, specificity 61%–85%),⁵ and ultrasound⁴ (sensitivity 76%, specificity 76%).⁷

Williams found 5 independent predictors of x-ray findings consistent with sinusitis in 247 male veterans:

• maxillary toothache (LR+, 2.5)
• no improvement with decongestants (LR+, 2.1)
• purulent secretions on exam (LR+, 2.1)
• abnormal transillumination (LR+, 1.6)
• colored nasal discharge (LR+, 1.5).³

In at least 2 of these 4 studies, purulent secretions in the nasal cavity (LR+, 2.1–5.5),^2,3 maxillary tooth pain (LR+, 2.1–2.5)^3,4 and purulent rhinorrhea (LR+, 1.5–1.9)^2,3,4 increased the likelihood of acute bacterial rhinosinusitis.

Finding purulent secretions in the nasal cavity is highly specific for acute bacterial rhinosinusitis (specificity 79%–100%)^1,2,3 but is uncommon and difficult to assess, requiring the use of a nasal speculum and possibly topical decongestants. The primary care physician’s overall clinical impression was accurate in Williams’ study but not in others.^2,4,6 Illness starting as the common cold and pain on bending forward were not predictors of acute bacterial rhinosinusitis.^2,3,4 Headache, bilateral maxillary pain, frontal sinus pain, fever, sinus tenderness on exam, and purulent pharyngeal discharge have not been shown to be useful in acute bacterial rhinosinusitis diagnosis.⁷

TABLE
Clinical prediction rule for acute bacterial rhinosinusitis