Anal lymphogranuloma venereum infection screening with IgA anti-Chlamydia trachomatis-specific major outer membrane protein serology.
BACKGROUND
Anal lymphogranuloma venereum (LGV) infections, caused by Chlamydia trachomatis biovar L (Ct+/LGV+), are endemic among men who have sex with men (MSM). Anal non-LGV biovar Ct infections (Ct+/LGV-) can be eradicated with 1 week doxycycline, whereas Ct+/LGV+ infections require 3-week doxycycline. To differentiate Ct+/LGV+ from Ct+/LGV- infections, biovar-specific Nucleic Acid Amplification Test (NAAT) are standard, but also expensive and laborious. A chlamydia-specific serological assay could serve as an alternative test.


METHODS
MSM were screened for anal Ct+/LGV+ and Ct+/LGV- infections with a commercial nonspecific NAAT and an in house biovar L-specific NAAT. Serum samples were evaluated with chlamydia-specific anti-Major Outer Membrane Protein (MOMP) and antilipopolysaccharide assays of IgA and IgG classes. Asymptomatic patients were identified as: (1) no anal complaints or (2) no microscopic inflammation (i.e., <10 leucocytes per high power field in anal smears). The best differentiating assay was subsequently evaluated in 100 Ct+/LGV+ and 100 Ct+/LGV- MSM using different cut-off points.


RESULTS
The anti-MOMP IgA assay was the most accurate to differentiate Ct+/LGV+ (n = 42) from Ct+/LGV- (n = 19) with 85.7% sensitivity (95% confidence interval [CI], 72.2-93.3) and 84.2% specificity (95% CI, 62.4-94.5), even among asymptomatic patients. In a population comprising 98 Ct+/LGV+ and 105 Ct+/LGV- patients, the anti-MOMP IgA assay scored most accurate when the cut-off point was set to 2.0 with 75.5% (95% CI, 65.8-83.6) sensitivity and 74.3% (95% CI, 64.8-82.3) specificity.


CONCLUSIONS
The IgA anti-MOMP assay can identify a considerable proportion of the (asymptomatic) anal LGV infections correctly. Yet, biovar L-specific NAAT are still the preferred diagnostic tests in clinical settings.
de Vries
Henry J C
HJ
STI outpatient clinic, Cluster Infectious Diseases, Public Health Service of Amsterdam (GGD Amsterdam), Amsterdam, The Netherlands. h.j.devries@amc.nl
Smelov
Vitaly
V
Ouburg
Sander
S
Pleijster
Jolein
J
Geskus
Ronald B
RB
Speksnijder
Arjen G C L
AG
Fennema
Johannes S A
JS
Morré
Servaas A
SA
D001004:Anus Diseases / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D019540:Area Under Curve; D002690:Chlamydia Infections / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D002692:Chlamydia trachomatis / Q000276:immunology*; D018451:Homosexuality, Male; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood*; D008219:Lymphogranuloma Venereum / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D008297:Male; D008403:Mass Screening / Q000379:methods*; D018272:Porins / Q000276:immunology*; D012680:Sensitivity and Specificity; D012698:Serologic Tests
D007070:Immunoglobulin A; D018272:Porins; C071677:omp1 protein, Chlamydia trachomatis