Testing for adenovirus
Adenovirus is the most frequent cause of acute conjunctivitis, responsible for approximately 25 percent of cases in the United States.7 Adenoviral conjunctivitis is considered to be highly contagious and frequently can lead to localized epidemics. Less than 5 percent of the population has antibodies effective against any serotype of adenoviral conjunctivitis. Adenovirus is remarkably robust and can resist heat and chemical disinfectants while remaining viable for up to five weeks.8
A confident diagnosis of adenovirus infection avoids the unnecessary use of antibiotics, which is important in reducing the risk of adverse events and multidrug resistance. Adenovirus infections can mimic preseptal and orbital cellulitis, especially in children, and this often leads to unnecessary hospital admissions, CT scans, and IV antibiotics. In one study, Ruttum et al revealed that 16 percent of patients with signs of preseptal or orbital infection were culture positive for adenovirus.9
Studies repeatedly show that skilled clinicians have difficulty reliably distinguishing between viral and bacterial conjunctivitis, especially during the first week after onset of symptoms.10 Rietveld examined a cohort of 184 adults with an acute red eye associated with symptoms of their eye being stuck shut in the morning and/or mucopurulent discharge. Of the 57 patients with confirmed bacterial conjunctivitis, 53 percent reported a history of one eye being stuck shut in the morning, while 39 percent reported bilateral involvement.11 Among 120 patients without bacterial conjunctivitis, 62 percent had one eye stuck shut, and 11 percent had bilateral involvement. Additionally, a clinical trial at 16 academic centers to evaluate cidofovir treatment showed that experts had a clinical accuracy of about 48 percent in correctly diagnosing the etiology of acute conjunctivitis.12
The AdenoPlus test has 90 percent sensitivity and 96 percent specificity when testing in the first seven days as compared to cell culture.7 After seven days, when the disease process typically transitions from infectious to inflammatory, approximately 25 percent of patients remain contagious at 10 days and 5 percent at two weeks.13
It is important to identify these patients through a positive AdenoPlus test result because they require more time away from work, school, or daycare. Conversely, a negative AdenoPlus test result supports the empirical diagnosis of bacterial conjunctivitis (after excluding allergic and fungal conjunctivitis). This supports the prescription of an appropriate antibiotic, as well as the patient’s return to work, school, or daycare after 24 to 48 hours.
An effective antiviral can significantly shorten adenoviral conjunctivitis, which may cause significant morbidity, protracted courses, and vision-compromising complications. Associated subepithelial infiltrates can impair visual acuity for months and significantly exacerbate chronic dry eye disease.12
Off-label use of ganciclovir ophthalmic gel 0.15%, which is FDA approved for treatment of herpes simplex epithelial keratitis (dendritic ulcers), has shown efficacy against adenoviral conjunctivitis in early clinical use.14 Evidence of ophthalmic efficacy came in a prospective study with 18 patients with adenoviral keratoconjunctivitis. Reported symptoms in the ganciclovir arm were less than half than in controls who received preservative-free tears (7.7 days vs. 18.5 days). Significantly fewer patients in the treatment group developed subepithelial opacities (two of nine vs seven of nine).