The new england journal of medicine n engl j med 351;9 www.nejm.org august 26, 2004 902 This Journal feature begins with a case vignette highlighting a common clinical problem. Evidence supporting various strategies is then presented, followed by a review of formal guidelines, when they exist. The article ends with the author's clinical recommendations.A 43-year-old man has a two-week history of nasal congestion, postnasal drip, and fatigue. He has used an over-the-counter nasal decongestant and acetaminophen, without relief. During the past few days, facial pain and pressure have developed and have not responded to decongestants. In addition, his nasal discharge has turned from clear to yellow. How should he be treated?Acute bacterial sinusitis is an infection of the paranasal sinuses with inflammation of the nose. On the basis of national population surveys and insurance-reimbursement claims, sinusitis is one of the most common health problems in the United States. 1 Acute bacterial sinusitis most commonly develops as a complication of a viral infection of the upper respiratory tract. Approximately 0.5 to 2 percent of cases of viral rhinosinusitis develop into bacterial infections. 2-4 Symptoms include nasal congestion, purulent nasal discharge, maxillary tooth discomfort, hyposmia or anosmia, cough, facial pain or pressure that is made worse by bending forward, headache, fever, and malaise. Physical findings include nasal turbinate edema, nasal crusts, purulence of the nasal cavity and posterior pharynx, and failure of transillumination of the maxillary sinuses. 5 Transillumination is performed in a completely darkened room by placing a flashlight against the skin overlying the infraorbital rim and directing the light inferiorly (Fig. 1). The patient then opens his or her mouth, and the hard palate is examined. The possible results are a palate that appears opaque or dull and a normal palate. However, the value of this procedure is limited; since it is not easy to perform, the clinician cannot differentiate viral from bacterial sinusitis, and results vary depending on the skill of the clinician. A particularly challenging task is to distinguish viral from bacterial sinusitis. In most patients, rhinoviral illness improves in 7 to 10 days 6 ; therefore, a diagnosis of acute bacterial sinusitis requires the persistence of symptoms for longer than 10 days or a worsening of symptoms after 5 to 7 days. Symptoms of viral sinusitis, including fever, mimic those of bacterial sinusitis, although the color and quality of nasal discharge -classically, clear and thin during viral sinusitis and yellow-green and thick during bacterial sinusitis -may help to differentiate the two.Studies over the past two decades have indicated that Streptococcus pneumoniae and Haemophilus influenzae are the major bacterial pathogens in adults with sinusitis. 7 Other species (including b -hemolytic and a -hemolytic streptococci, Staphylococcus aureus, and anaerobes) have also been cultured from adults with sinusitis but are much less frequ...