Diagnosis of Chlamydiainduced Reactive Arthritis
Internal medicine (Tokyo. 1992)
Ishii et al described Chlamydia-induced reactive arthritis in a patient without urethritis but in whom Chlamydia was identified by a combination of serology (immunoglobulin G (IgG) and IgA type antibodies) and polymerase chain reaction (PCR) (1). We encountered an arthritis patient with false positive test results for IgA antibody. The 46-year-old man was referred with a history of multiple joint pain lasting 2 months and with an elevated C-reactive protein level (7.8 mg/dl). Laboratory test
... Laboratory test results at the referring hospital showed positivity for IgG and IgA antibodies to Chlamydia trachomatis but no pyuria. He did not deny a pertinent sexual history for C. trachomatis, and he requested treatment. Minocyclin was prescribed but was not effective. Laboratory tests at our hospital showed positivity for IgG and negativity for IgA antibodies to C. trachomatis. Results of PCR were negative. Skin rash was noted on the patient's back, and psoriatic ar-thritis was diagnosed. Cyclosporin A was administered and was very effective for both the skin rash and the arthritis. IgG and IgA type antibodies are measured to diagnose C. trachomatis, because IgM antibody, which is used as a marker of acute phase infection, cannot be measured for C. trachomatis. However, positivity for IgA antibody does not necessarily indicate C. trachomatis infection, and Chlamydia infection is not always marked by positivity for IgA antibody (2). PCR is highly sensitive and specific, and there is absolutely no cross-reactivity with C. pneumoniae or C. psittaci. In men, first-void urine specimens can be used, but first-void urine specimens are not appropriate for detecting C. trachomatis infection in women because of the likelihood of false-negative results (3). Therefore, first-void urine should be used only for women from whom it is difficult to obtain cervical swab specimens (3). However, when C. trachomatis progresses into the fallopian tube or intraperitoneum, cervical swab specimens sometimes show a false negative result. Titers of IgG and IgA antibodies to C. trachomatis are high in such conditions and effective in predicting intrapelvic infection (4). Therefore, clinical diagnosis based on a combination of antibodies to C. trachomatis and PCR is very important. In November 2004, strand displacement amplification (SDA) was approved in Japan for the diagnosis of C. trachomatis. SDA has sensitivity and specificity similar to those of PCR and is accomplished more easily (5). We expect use of SDA to increase in Japan for diagnosis of C. trachomatis. References 1. Ishii W, Matsuda M, Okamoto N, et al. Reactive arthritis due to asymptomatic infection of Chlamydia trachomatis. Intern Med 44: 509-510, 2005. 2. Takahashi K, Shioda K, Tobai H, et al. Clinical study of the characteristics and limitation of diagnostic method for anti-Chlamydial antibodies. Nippon Sanka Fujinka Gakkai Zasshi 46: 925-928, 1994 (in Japanese). 3. Sagiyama K, Yasumoto T, Uraba H, et al. Evaluation of Amplicor AMPLICOR R Chlamydia trachomatis kit in first-void urine specimens of women. Jpn Arch Sex Transmit Dis 6: 46-50, 1995 (in Japanese with English abstract). 4. Fujita M, Noguchi Y, Noguchi M, et al. Chlamydia trachomatis infection and intra pelvic adhesion.