Question
What are the laboratory methods for the diagnosis of gonorrhea and syphilis infections?

Main Results
For diagnosis of N. gonorrhoeae, swabs of the endocervix and of the urethra of women and men are taken.  Rectal and/or oropharyngeal swabs should also be taken depending on the patient’s sexual history.  Gram stains are examined for Gram-negative diplococci in polymorphonuclear leukocytes.  The sensitivity of Gram stains for N. gonorrhoeae diagnosis is 89 to 96% for men and 31 to 51% for women.  Swabs are inoculated onto agar plates for culture, which is simple, inexpensive, sensitive, specific, and allows for antimicrobial sensitivity testing of the isolate.  N. gonorrhoeae can be detected using DNA detection with and without amplification.  These tests can be performed on urine, vaginal, urethral, and cervical samples with high sensitivity (95%) and specificity (99%) in symptomatic patients from high prevalence populations.  Positive cases in low prevalence settings require confirmation with a second assay.  Culture confirmation and sensitivity testing or a test-of-cure following treatment in patients who are positive by DNA tests are essential.

T. pallidum is diagnosed by demonstrating the presence of the organism in specimens taken from the patient’s lesion, including dark-field and fluorescent microscopy and PCR; or by detecting antibodies in serum.  Unlike darkfield microscopy, staining with fluorescent anti-T. pallidum antibodies is specific and suitable for oral and rectal lesions.  Non-treponemal serological tests include VDRL and RPR.  Quantification of the response in these tests allows assessment of stage of infection and response to treatment.  False-positive results may occur.  Treponemal tests detect antibodies specific to T. pallidum and include EIA, TPHA, TPPA, and FTA-ABS.  They have high sensitivity and specificity and are suited to automation.  EIA positive results should be confirmed with another test, usually the TPHA or TPPA.  

Authors’ Conclusions
The rapid diagnoses of gonorrhea and syphilis can often be provided using near-patient microscopy methods.  

Source of funding:  None given.