Value of serology in diagnosing Lymphogranuloma venereum

Abstract number: p562

Meyer  T., Noah  C., Arndt  R., Stellbrink  H.J., Unger  S., Plettenberg  A.

Objective and background: 

An outbreak of Lymphogranuloma venereum (LGV) caused by Chlamydia trachomatis L2 was reported recently among MSM in Europe. Confirmed diagnosis of LGV requires identification of C. trachomatis L-genotypes in symptomatic patients. However, due to the invasiveness of LGV-strains they may not always be detectable in lesional swabs. Since LGV is associated with induction of a strong antibody response, serology may be helpful in identifying affected patients, even retrospectively. To characterize the predictive value of serology for LGV, serum samples of patients with and without C. trachomatis infections were analyzed using different commercial C. trachomatis antibody tests

Methods: 

Serum specimens from patients with invasive C. trachomatis infection (LGV) (n = 15), epithelial C. trachomatis infection (urethritis, cervicitis) (n = 17), and without any evidence for infection with C. trachomatis (n = 20) were tested for antibodies against C. trachomatis by complement fixation (CF), LPS-based (genus-specific) EIA (LPS-EIA), MOMP-based (C. trachomatis-specific) EIA (CT-EIA) and a line assay with recombinant antigens (LA). Presence or absence of C. trachomatis was analyzed by SDA of anogenital swabs obtained from these patients.

Results: 

Specificity and sensitivity for LGV was 89.2% and 93.3% (CF), 92.9% and 73.3% (LPS-EIA, IgA), 94.6% and 26.7% (LPS-EIA, high IgG), 73.0% and 86.6% (CT-EIA, IgA), 91.9% and 73.3% (CT-EIA, high IgG), 86.2% and 85.7% (LA, IgA), and 75.9% and 85.7% (LA, high IgG). Assuming a prevalence of 20% (confirmed cases among patients suspicious of LGV) the PPV ranges between 44.5% (CT-EIA, IgA) and 72.1% (LPS-EIA, IgA). NPVs were higher, ranging between 81.0% (LPS-EIA, high IgG) and 98.2% (CF).

Conclusion: 

Positive serology (IgA-positive or high IgG titre) does not necessarily indicate LGV, but may also result from C. trachomatis infections caused by non-L strains, whereas in case of negative serology the presence of LGV is very unlikely.