How are the Paraclinical Diagnoses of Gonorrhea Regulated?
Pursuant to Subsection 2.2, Section 2 of the Diagnosis and Treatment Guidelines for Gonorrhea (issued with Decision 5165/QD-BYT in 2021), the regulations for clinical diagnosis of gonorrhea are as follows:
Gram Stain
- Gram stain shows Gram-negative diplococci in coffee-bean shape within and outside polymorphonuclear leukocytes.
- This is an easy and inexpensive test that is valuable for preliminary diagnosis of gonorrhea, particularly in symptomatic male patients. However, only 50-70% of asymptomatic gonorrhea cases in males are positive with Gram stain, therefore a negative Gram stain is not sufficient to rule out the disease.
- Gram stain testing is less reliable for cervical and rectal specimens due to low sensitivity (sensitivity for cervical specimens is 30-50%).
Culture
- Culturing gonococci on Thayer-Martin medium containing vancomycin is the gold standard for diagnosis (sensitivity for urethral and cervical gonorrhea is 85-95%), and simultaneously determines the antibiotic sensitivity of Neisseria gonorrhoeae through antibiotic susceptibility testing.
- Optimal isolation of N. gonorrhoeae requires proper specimen collection, prompt culturing on appropriate media, correct transportation, and incubation under proper conditions.
- The highest positive specimen collection sites in males are the urethra, and in females, the cervix.
Nucleic Acid Amplification Tests (NAATs)
- Nucleic Acid Amplification Tests (or genetic amplification tests, including PCR tests) are used to detect the nucleic acid of Neisseria gonorrhoeae.
- NAATs have high specificity and sensitivity (sensitivity above 90%), higher compared to culture, and can be used with various types of specimens such as urine, vaginal secretions, cervical secretions, and urethral discharge. Different NAAT techniques have varying sensitivities, with rectal and pharyngeal specimens typically having lower sensitivity.
- The most common NAAT test currently is multiplex Real-time PCR, often combining the diagnosis of both gonorrhea and Chlamydia at the same time.
- Limitation: It does not provide information on the antibiotic sensitivity of the bacteria.
Respectfully!
