MGRNA - Clinical: Neisseria gonorrhoea, Miscellaneous Sites, by Nucleic Acid Amplification (GEN-PROBE)

Test Catalog

Test ID: MGRNA    
Neisseria gonorrhoea, Miscellaneous Sites, by Nucleic Acid Amplification (GEN-PROBE)

Useful For Suggests clinical disorders or settings where the test may be helpful

Detection of Neisseria gonorrhoeae

Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.

This test is used for specimens that are not FDA approved for this assay. Acceptable non-FDA-approved specimen types are ocular, oral, anal or rectal swabs, and peritoneal fluid.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Gonorrhea is caused by the bacterium Neisseria gonorrhoeae. It is also a very common sexually transmitted infection (STI), with 301,174 cases of gonorrhea reported to CDC in 2009.(1,2) Many infections in women are asymptomatic and the true prevalence of gonorrhea is likely much higher than reported. The organism causes genitourinary infections in women and men and may be associated with dysuria and vaginal, urethral, or rectal discharge. Complications include pelvic inflammatory disease in women and gonococcal epididymitis and prostatitis in men. Gonococcal bacteremia, pharyngitis, and arthritis may also occur. Infection in men is typically associated with symptoms that would prompt clinical evaluation. Given the risk for asymptomatic infection in women, screening is recommended for women at increased risk of infection (eg, women with previous gonorrhea or other STI, inconsistent condom use, new or multiple sex partners, and women in certain demographic groups such as those in communities with high STI prevalence).(1,2) The CDC currently recommends dual antibiotic treatment due to emerging antimicrobial resistance.(2)

 

Culture was previously considered to be the gold standard test for diagnosis of N gonorrhoeae infection. However, organisms are labile in vitro, and precise specimen collection, transportation, and processing conditions are required to maintain organism viability, which is necessary for successful culturing. In comparison, nucleic acid amplification testing (NAAT) provides superior sensitivity and specificity and is now the recommended method for diagnosis in most cases.(2-5) Immunoassays and nonamplification DNA tests are also available for Neisseria gonorrhoeae detection, but these methods are significantly less sensitive and less specific than NAATs.(2-5)

 

Improved screening rates and increased sensitivity of NAAT testing have resulted in an increased number of accurately diagnosed cases.(2-5) Improved detection rates result from both the increased performance of the assay and the patients' easy acceptance of urine testing. 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.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative

Interpretation Provides information to assist in interpretation of the test results

A positive result indicates the presence of rRNA of Neisseria gonorrhoeae.

 

A negative result indicates that rRNA for N 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 N gonorrhoeae), if appropriate.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

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 (ie, 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. 

 

No interference is expected with swab specimens due to:

-Blood  

 

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 with gonococcal infections may miss some infected individuals.

 

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.

Supportive Data

Accuracy/Diagnostic Sensitivity and Specificity

 

Accuracy:

 

1. Clinical Specimens

Non-FDA approved specimen types were collected in GEN-PROBE APTIMA collection devices according to the manufacturer’s instructions and tested using the GEN-PROBE APTIMA Combo 2 assay on the Tigris DTS System. Results were compared to those obtained by other CLIA-certified laboratories using the GEN-PROBE Tigris system. All specimens were within product insert stability requirements at the time of testing on the GEN-PROBE Tigris system. Clinical specimens were stored frozen until the time of testing. 

 

Non-FDA Approved Sources for detection of Neisseria gonorrhoeae (see additional spiking studies below):

Oral/Throat

 

Reference result

Aptima Unisex

 

Positive

Negative

Total

APTIMA (Mayo)

Positive

20

0

20

Negative

0

49

49

Total

20

49

69

 

Anorectal

Reference result

Aptima Vaginal Self

Collect Kit

Positive

Negative

Total

APTIMA (Mayo)

Positive

8

1

9

Negative

1

18

19

Total

9

19

28

 

Peritoneal Fluid

 

Reference result

Aptima Vaginal Self

Collect Kit

 

Positive

Negative

Total

APTIMA (Mayo)

Positive

0

0

0

Negative

0

10

10

Total

0

10

10


2. Spiked Specimens:

Negative specimens were spiked at the approximate limit of detection (LoD) and tested to supplement clinical specimen validation data (see analytical sensitivity validation data below).

Source

Positives

(Number tested)

Negatives

(Number tested)

Concordance

Oropharyngeal (throat)

10 (10)

0 (0)

100%

Anorectal

23 (23)

0 (0)

100%

Peritoneal Fluid

30 (30)

0 (0)

100%

Ocular

30 (30)

46 (46)

100%

 

3. M5 media:

One milliliter of M5 media was added to GEN-PROBE APTIMA Specimen Transfer Kit collection devices and then spiked at the LoD for N gonorrhoeae. This was performed to determine if the M5 media interfered with detection of N gonorrhoeae, and to determine if future specimens submitted in M5 media could be tested in this manner. Thirty-one specimens were spiked near the LoD, while 14 specimens had M5 media added, but no organism was spiked into the sample.

M5 Media

Positives

(Number tested)

Negatives

(Number tested)

Agreement

 

31 (31)

14 (14)

100%

 

4. Total Accuracy (Clinical and spiked specimens combined):

Source

Collection Device*

Total Tested**

Sensitivity

Specificity

Positive

(Number tested)

Negative

(Number tested)

Oropharyngeal (throat)

Unisex

30 (30)

49 (49)

100%

100%

Anorectal

Vaginal Self Collect

31 (32)

19 (19)

97%

100%

Peritoneal fluid

Vaginal Self Collect

30 (30)

10 (10)

100%

100%

Ocular

Unisex

30 (30)

46 (46)

100%

100%

 

*All collection devices are manufactured by GEN-PROBE for use with the Aptima assay

** Positive and negative status are based on the result by the comparator method (clinical specimens) or expected result (spiked specimens)

 

Analytical Sensitivity (LoD):                              

The LoD was established by preparing dilutions of N gonorrhoeae (ATCC strain 43069). The LoD was determined to be 12.5 CFU/assay (colony forming units). Although specimens diluted to a final concentration of 12.5 CFU/assay gave 100% positive results, we chose only to test the analytical sensitivity claim in the product insert, which is 50 CFU/assay. The LoD was confirmed in all non-FDA approved specimens that will be accepted for testing with this assay (oropharyngeal/throat, ocular, and miscellaneous anogenital specimens). Clinical specimens of each source/grouping were spiked with N gonorrhoeae at 50 CFU/assay and tested with positive and negative controls as per standard protocol. 

 

Summary of Results:

Specimen Type

Limit of Detection

Number Positive

(Number tested)

% Positive

Oropharyngeal/Throat

50 CFU/assay

30 (30)

100

Ocular

50 CFU/assay

30 (30)

100

Anorectal

50 CFU/assay

23 (23)

100

Peritoneal fluid

50 CFU/assay

30 (30)

100

 

Analytical Specificity:

To augment the specificity panel performed by GEN-PROBE as outlined in the APTIMA product insert, an additional panel was tested by the GEN-PROBE Tigris DTS System using the APTIMA COMBO 2 Assay. Analyte-negative patient specimens collected in GEN-PROBE collection devices were spiked with specificity panel organisms and tested. Organisms were chosen based on their ability to cause disease similar to N gonorrhoeae or be normal flora in non-FDA approved specimen sources. The assay did not cross-react with any members of the specificity panel.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

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: Sexually Transmitted Diseases Treatment Guidelines, 2010. MMWR Morb Mortal Wkly Rep 2010;59:RR12

3. Crotchfelt KA, Pare B, Gaydos C, Quinn TC: Detection of Chlamydia trachomatis by the GEN-PROBE AMPLIFIED Chlamydia trachomatis Assay (AMP CT) in urine specimens from men and women and endocervical specimens from women. J Clin Microbiol 1998 Feb;36(2):391-394

4. Gaydos CA, Quinn TC, Willis D, et al: Performance of the APTIMA Combo 2 assay for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in female urine and endocervical swab specimens. J Clin Microbiol 2003 Jan;41(1):304-309

5. Chernesky MA, Jang DE: APTIMA transcription-mediated amplification assays for Chlamydia trachomatis and Neisseria gonorrhoeae. Expert Rev Mol Diagn 2006 Jul;6(4):519-525