Diagnosing Neisseria gonorrhoeae infections.

Neisseria gonorrhoeae, a gram-negative bacterium, is a common

cause of sexually transmitted infection. This organism causes

dysuria and urethral discharge in males with acute urethritis;

complications may include pelvic inflammatory disease in women,

and ascending infection resulting in gonococcal epididymitis and

prostatitis in men.

Neisseria gonorrhoeae is labile and does not remain viable for

sustained periods of time. Diagnosis by culture methods, rather

than NAT testing, especially after extended transit times, is not

recommended. Previously, culture was considered the gold

standard test for diagnosis of Neisseria gonorrhoeae infections.

However, the organisms are labile in vitro, and precise specimen

collection, transportation, and processing conditions are required

to maintain organism viability, a necessity for culturing. Nucleic acid

amplification testing (NAAT), which detects DNA of the organism,

does not require the organism to be alive, is much more sensitive

than culture, and is now considered the preferred test for detecting

Neisseria gonorrhoeae.

Improved screening rates and increased sensitivity of NAAT testing

translate to increased numbers of accurately diagnosed cases.

Improved detection rates resulting from both increased assay performance

and patients' easy acceptance of urine testing, combined with appropriate

treatment, decrease disease burden and spread.(3) Early identification of

infection enables sexual partners to seek testing and/or treatment as soon

as possible and reduces the risk of disease spread. Prompt treatment

reduces the risk of infertility in women.

Negative

A positive result indicates the presence of DNA of Neisseria

gonorrhoeae.

A negative result indicates that DNA for Neisseria gonorrhoeae

was not detected in the specimen.

The predictive value of an assay depends on the prevalence of

the disease in any particular population. In settings with a high

prevalence of sexually transmitted disease, positive assay results

have a high likelihood of being true positives. In settings with a low

prevalence of sexually transmitted disease, or in any settings in

which a patient's clinical signs and symptoms or risk factors are

inconsistent with gonococcal or chlamydial urogenital infection,

positive results should be carefully assessed and the patient

retested by other methods (eg, culture for Neisseria gonorrhoeae),

if appropriate.

This report is intended for use in clinical monitoring or management

of patients; it is not intended for use in medico-legal applications.

Appropriate specimen collection and handling is necessary for

optimal assay performance.

Results should be interpreted in conjunction with other laboratory

and clinical information.

A negative test result does not exclude the possibility of infection.

Improper specimen collection, concurrent antibiotic therapy,

presence of inhibitors, or low numbers of organisms in the

specimen (i.e., below the sensitivity of the test) may cause

false-negative test results.

In low prevalence populations, positive results must be interpreted

carefully as false-positive results may occur more frequently than

true-positive results in this setting.

This assay cannot be used to assess therapeutic success or failure,

since nucleic acids from the organism may persist following

antimicrobial therapy.

The assay may cross-react with Neisseria cinerea and Neisseria

lactamica (normal flora of the upper respiratory tract) and cause

false-positive results. Consequently, nasal, throat, and oral (mouth)

specimens will be rejected.

The following may cause indeterminate or false-negative results:

  -Specimens with moderate to gross blood content

  -Presence of highly pigmented substances in urine, such as bilirubin 

   or phenazopyridine (10 mg/mL)

  -Very high white cell count (>250,000 cells/mL)

  -Talcum powder or deodorant sprays in urine specimens

The effects of other potential variables, such as vaginal discharge, use

of tampons, douching, and specimen types other than those listed in

Specimen Required, and specimen collection variables have not been

determined.

Testing of urine specimens with this method is not intended to replace

cervical exam and endocervical sampling for diagnosis of urogenital

infection; infections may result from other causes or concurrent infections

may occur.

Testing urine specimens as the sole test for identifying female patients

gonococcal infections may miss infected individuals with this assay.

Performance estimates for urine specimens are based on evaluation

of urine obtained from the first part of the urine stream; performance on

midstream collections has not been determined.

Performance characteristics for detecting Neisseria gonorrhoeae

in males are based on testing patients with infection rates of

27% to 43%. The male populations sampled were from sexually

transmitted disease (STD) clinics where the prevalence of

Neisseria gonorrhoeae is higher than in other clinical settings.

Likewise, the majority of females in the study with Neisseria

gonorrhoeae infections were from STD clinics. In the low

prevalence setting (1.2% prevalence), only 6 gonococcal

infections were identified. Positive results in low prevalence

populations should be interpreted carefully in conjunction with

clinical signs and symptoms, patient risk profile, and other

findings and the understanding that the likelihood of a false-

positive may be higher than a true-positive.

1.   Centers for Disease Control and Prevention. 2002. Reporting

      of laboratory-confirmed chlamydial infection and gonorrhea

      by providers affiliated with three large Managed Care

      Organizations - United States, 1995-1999. MMWR Morb Mortal

      Wkly Rep 2002;51:256-259

2.   Centers for Disease Control and Prevention: Screening Tests

      To Detect Chlamydia trachomatis and Neisseria gonorrhoeae               

      Infections—2002. Morbidity and Mortality Weekly Report

      Recommendations and Reports October 18, 2002;Vol. 51; No RR-15

3.   Chan EL, Brandt K, Olienus K, et al:  Performance characteristics

      of the Becton Dickinson ProbeTec System for direct detection of

      Chlamydia trachomatis and Neisseria gonorrhoeae in male and

      female urine specimens in comparison with the Roche Cobas

      System. Arch Pathol Lab Med 2000;124(11):1649-1652