Diagnosis of viral and chlamydial keratoconjunctivitis: which laboratory test?

Conjunctivitis and keratitis are common forms of ocular morbidity seen in general practice and eye units. 2 The aetiology of these diseases includes viral, bacterial, or parasitic infection as well as allergy, trauma, and dietary deficiency. Among the common microbial causes (Table 1) are adenovirus, herpes simplex virus (HSV), and Chlamydia trachomatis. Ocular adenovirus infections occur throughout the world in both sporadic and epidemic forms, and large scale outbreaks of epidemic keratoconjunctivitis can occur in hospitals, schools, military establishments, or factories. HSV type 1 ocular infection occurs in all countries with an annual incidence of up to 20.7 per 100 000 population and is the most common infective cause of blindness in developed countries. 9 Trachoma caused by C trachomatis serovars A–C is the leading infectious cause of blindness in the world and is a major public health problem in developing countries. Adult chlamydial conjunctivitis, caused by C trachomatis serovars D–K, is an oculogenital infection and up to 90% of patients have concurrent genital infection. Chlamydial neonatal conjunctivitis (ophthalmia neonatorum) develops in 18%–74% of babies born to mothers with genital chlamydial infection. This article reviews available diagnostic laboratory techniques for keratoconjunctivitis caused by adenovirus, HSV, and C trachomatis with special emphasis on modern molecular diagnostic techniques. For information on the clinical features, epidemiology, and treatment of these infections the reader is referred to a number of other reviews. 9 14–17 The need for laboratory investigation Owing to the limited reliability of clinical diagnosis of adenovirus, HSV, and C trachomatis induced keratoconjunctivitis, accurate laboratory investigation for these agents in conjunctival swabs is often valuable. Failure to diagnose ocular adenoviral disease can result in outbreaks of epidemic keratoconjunctivitis. Prompt recognition of the strains of adenovirus causing this condition in patients can, however, help to contain the development of a hospital based epidemic. C trachomatis infection (particularly with serovars D–K) is usually associated with asymptomatic genitourinary colonisation. Misdiagnosis of this ocular infection may represent a missed opportunity to detect infection of the genital tract which can ultimately result in a series of complications including pelvic inflammatory disease, epididymitis, ectopic pregnancy, and infertility in the patient and/or partner. 25 In addition, delay in diagnosing chlamydial conjunctivitis and the use of inappropriate antibiotic treatment might trigger chlamydial persistence. The availability of appropriate treatment for chlamydia, HSV, and possibly adenovirus together with the potentially serious residual morbidity of these infections clearly justifies the need for accurate laboratory investigation in cases of keratoconjunctivitis.