IPAzyme Chlamydia and microimmunofluorescence tests for detecting antibodies against Chlamydia trachomatis in women undergoing laparoscopy

Superficial Chlamydia trachomatis infections are diagnosed by antigen detection whereas serological investigations are mainly performed to detect deep-seated infections. In this study the genus-specific IPAzyme and two species-specific microimmunofluorescence (MIF) tests were compared for detecting antibodies against C. trachomatis in women undergoing laparoscopy for diagnostic purposes or for ligation of the fallopian tubes. Microbiological findings were similar in both groups. C. trachomatis was detected in 4 of 38 women with ligation and in 6 of 61 women with diagnostic laparoscopy. Serum IgG antibody titres by IPAzyme were clearly positive in 24 out of 61 of the diagnostic group and in 12 out of 38 of the ligation group. However, 14 (39%) of the 36 IPAzyme-positive results were caused by antibodies against Chlamydia pneumoniae and/or Chlamydia psittaci, only 4 (11%) were caused by anti-C. trachomatis IgG and 8 (22%) were caused by both antibodies as tested by a conventional MIF; in 10 all MIF titres were lower than 1:32. A commercial MIF still containing too much genus-specific lipopolysaccharides was more sensitive, but also more crossreactive than the conventional MIF. IPAzyme IgA were only found in association with positive IPAzyme IgG results. We conclude that in case of presumed deep-seated C. trachomatis infection only sensitive species-specific assays for detecting C. trachomatis antibodies are helpful. IPAzyme and other genus-specific assays cannot be recommended to detect antibodies to C. trachomatis in the serum, because positive results are caused mainly by antibodies against respiratory chlamydiae.