Direct fluorescent antibody assay and polymerase chain reaction for the detection of Chlamydia trachomatis in patients with vernal keratoconjunctivitis

Abstract

OBJECTIVES:To identify Chlamydia trachomatis via polymerase chain reaction and a direct fluorescent antibody assay in patients with vernal keratoconjunctivitis while comparing the efficacies of both tests for detecting Chlamydia trachomatis in these conditions.METHODS:Conjunctival scraping samples were obtained from 177 patients who were divided into two groups: a vernal keratoconjunctivitis group (group A) and a control group (group B). The polymerase chain reaction and a direct fluorescent antibody assay were performed. Sensitivity, specificity, receiver operating characteristic curves, and areas under the curve were calculated for both tests in groups A and B. Receiver operating characteristic curves were plotted using a categorical variable with only two possible outcomes (positive and negative).RESULTS:Statistical analysis revealed a significant association between vernal keratoconjunctivitis and Chlamydia trachomatis infection detected by a direct fluorescent antibody assay with high sensitivity and specificity. All patients in group A with positive polymerase chain reactions also presented with positive direct fluorescent antibody assays.CONCLUSION:The association between vernal keratoconjunctivitis and Chlamydia trachomatis infection was confirmed by positive direct fluorescent antibody assays in 49.4% of vernal keratoconjunctivitis patients and by positive polymerase chain reactions in 20% of these patients. The direct fluorescent antibody assay detected Chlamydia trachomatis in a higher number of patients than did the polymerase chain reaction. Although the diagnosis of trachoma is essentially clinical, the disease may not be detected in vernal keratoconjunctivitis patients. Due to the high frequency of chlamydial infection detected in patients with vernal keratoconjunctivitis, we suggest considering routine laboratory tests to detect Chlamydia trachomatis in patients with severe and refractory allergic disease.

Validation of a duplex qPCR for detection of Chlamydia trachomatis DNA in ocular samples and comparison with a direct immunofluorescence method using samples from endemic and non-endemic areas in Brazil

“…trachomatis still is, in many countries, clinical inspection of the patient's inverted eyelid [32,33], while some use DFA [9,10]. Very few diagnostic facilities perform molecular tests for trachoma determination.…”

“…DFA uses fluorescent monoclonal antibodies to detect the presence of a C. trachomatis specific protein (MOMP) or polyclonal antibodies against lipopolysaccharide (LPS) [7]. However, despite displaying high specificity, DFA's sensitivity is low [8][9][10], possibly because trachoma sampling is affected by several factors, such as previous recent use of eyewash by the patient, associated infections or even the stage of the infection. Micro immunofluorescence methods use serovars-specific monoclonal antibodies, which increases the sensitivity for C. trachomatis detection but is a laborious technique that requires a trained technician to analyze the data, thus limiting its use [11].…”

Tracoma: de lo básico a lo clínico

“…Esta prueba es una buena opción en las etapas tempranas y asintomáticas de la enfermedad en las que es difícil la diferenciación con otras conjuntivitis, sean bacterianas o virales; su uso está limitado porque se requieren condiciones estrictas de transporte y almacenamiento refrigerados, un microscopio fluorescente y personal adecuadamente entrenado (42).…”

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“…Adenovirus studies are described in two articles. Nishiwaki-Dantas et al (10) who sought to identify Chlamydia trachomatis via polymerase chain reaction vs. direct fluorescent antibody assay in patients with vernal keratoconjunctivitis. The direct fluorescent antibody assay detected Chlamydia trachomatis in a 49.4% of vernal keratoconjunctivitis patients, while the polymerase chain reaction only succeeded in 20% of cases.…”