IMPORTANCE Acute infectious conjunctivitis is characterized by ocular redness and discharge, and is a common clinical entity. Evidence-based tools to aid the clinical diagnosis of viral vs bacterial conjunctivitis are lacking and may contribute to overprescribing of topical antibiotics.OBJECTIVE To determine the relative prevalence of viral vs bacterial conjunctivitis in adults and children, and to determine which symptoms or signs are suggestive of a viral vs bacterial etiology.DATA SOURCES A MEDLINE search (January 1946-March 2022) yielded 1891 articles. Included articles were rated using a quality score based on a modified Rational Clinical Examination grading system. Methodological quality levels 1 through 4 required a microbiological reference standard for diagnosis, whereas quality level 5 (the lowest quality) used a clinical reference standard for diagnosis.STUDY SELECTION Consecutive series of patients presenting with acute infectious conjunctivitis and case series of viral or bacterial conjunctivitis alone. Thirty-two studies were included in a meta-analysis to determine prevalence and diagnostic accuracy measures; 27 used a microbiological reference standard for diagnosis and 5 used a clinical reference standard for diagnosis.
RESULTSIn studies involving children (5 studies; 881 patients; mean age, 4.7 years [age range, 1 month-18 years]), the prevalence of bacterial conjunctivitis was higher than viral conjunctivitis (71% vs 16%, respectively, P = .01). In the only study of adults (n = 207 patients; mean age, 25.7 years), the prevalence of viral conjunctivitis was higher than bacterial conjunctivitis (78% vs 16%, respectively, P < .001). For the primary analysis of level 1 (n = 6) and level 2 (n = 5) studies (1725 patients total), the clinical findings that best distinguished a viral etiology for conjunctivitis from a bacterial etiology included pharyngitis (sensitivity range, 0.55-0.58; specificity range, 0.89-0.94; positive likelihood ratio [LR] range, 5.4-9.9), preauricular lymphadenopathy (sensitivity range, 0.17-0.31; specificity range, 0.93-0.94; positive LR range, 2.5-5.6), and contact with another person with red eye (