Sinusitis, which affects an estimated 30 million American adults annually, is defined as symptomatic inflammation of the paranasal sinuses and nasal cavity.1 It is also often referred to as acute rhinosinusitis.

Sinusitis is classified as acute — lasting up to 4 weeks — chronic — lasting more than 3 months — or subacute — lasting between 4 weeks and 3 months. It is further classified according to the presumed cause: viral or bacterial.2 The most common etiology of sinusitis is viral, followed by allergic; bacterial is the least common. A viral infection can also progress into a bacterial infection. Fungal pathogens may be considered, especially in immunocompromised individuals.


For most immunocompetent patients, the diagnosis of sinusitis involves distinguishing between the signs and symptoms of viral and bacterial infections. The main clinical characteristics of acute sinusitis include nasal congestion, facial pain and/or pressure, rhinorrhea, post-nasal drainage, headache, and cough. Updated clinical practice guidelines from the American Academy of Otolaryngology-Head and Neck Surgery Foundation (AAO-HNS) recommend a diagnosis of acute bacterial rhinosinusitis (ABRS) when the following conditions are met:

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  1. Symptoms or signs of sinusitis (purulent drainage accompanied by nasal obstruction, facial pain, pressure, fullness, or both) persist without improvement for at least 10 days beyond the onset of upper respiratory symptoms, or
  2. Symptoms or signs of sinusitis worsen within 10 days after an initial improvement (double worsening).3

Even though providers use symptom duration and purulent discharge as a way to differentiate between viral or bacterial causes, there is no high-level evidence to support this.3 Physical findings — even color of nasal discharge — do not reliably predict a bacterial infection.3,4  Discolored nasal discharge is a sign of inflammation and related to the presence of neutrophils, not bacteria.3 Using fever and facial or dental pain to distinguish between a viral or bacterial source is also not supported by evidence and should not be used in decision making about whether to prescribe antibiotics.1

Differentiating viral rhinosinusitis (VRS) from ABRS is a significant challenge. Viral and bacterial infections both present similarly; a viral infection often precedes bacterial infection. There is currently no test, sign, or symptom that can clearly identify those patients who have a bacterial infection and would benefit from antibiotics. 

The sensitivity and specificity of current diagnostic imaging is insufficient. Radiographic imaging is not recommended for distinguishing between ABRS and VRS, unless a complication or alternative diagnosis is suspected.3 Sinus puncture and culture are the gold standard for microbial identification, but routine use is not recommended.5

The Clinical Problem

Up to 90% of patients with viral upper respiratory tract infections have concurrent VRS; according to epidemiological estimates, only 0.2% to 2% have sinusitis that progresses to ABRS.1,6 Sinusitis will often resolve in most patients without antibiotic treatment, even if it is bacterial in origin.

Despite this, sinusitis continues to be the fifth-leading reason for antibiotic prescriptions nationwide.6 Antibiotics are prescribed for 84% to 91% of patients with acute sinusitis who are diagnosed in the emergency department or outpatient settings.1 The persistent high rate of antibiotic prescribing is likely multifactorial; reasons may include:

  • A patient’s desire for a tangible “prescription” from the clinical encounter
  • Provider’s desire to satisfy the patient or other clinical demands
  • Lack of information on behalf of the patient or provider
  • Strong concern that the patient, if left untreated, may develop the rare complications of a bacterial infection that spreads beyond the sinus cavity.4

Studies suggest that the latter complications can occur regardless of whether or not the patient was treated with an antibiotic.4

The current over-prescribing of antibiotics has led to a substantial increase in drug-resistant pathogens — an urgent public health threat in the US. This has led to increased mortality, morbidity, and cost.3 Increasing bacterial resistance, coupled with the decrease in development of new antibiotics, signals a need for better alternative interventions to treat the symptoms of patients presenting to ambulatory care settings with sinus symptoms.