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Test Code MGRNA Neisseria gonorrhoeae, Miscellaneous Sites, by Nucleic Acid Amplification

Reporting Name

N. gonorr, Misc, Amplified RNA

Useful For

Detection of Neisseria gonorrhoeae for non-FDA approved specimen types

Method Name

Transcription Mediated Amplification

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Varies


Advisory Information


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. For FDA-approved specimen types, order GCRNA / Neisseria gonorrhoeae by Nucleic Acid Amplification.



Necessary Information


Specimen source is required.



Specimen Required


Swab specimens must be collected using an Aptima Collection Unisex Swab (T583) or Aptima Collection Multitest Swab (T584). These swabs are contained in the Aptima Collection Kit.

 

Submit only 1 of the following specimens:

 

Supplies:

Swab, Aptima Male/Female Collection (T583)

Swab, Aptima Multitest Swab Specimen Collection Kit (T584, formerly called Aptima Vaginal Swab Specimen Collection Kit)

Specimen Type: Oral/throat or ocular (corneal/conjunctiva) or rectal/anal

Container/Tube: Aptima Collection Multitest Swab (T584), or Aptima Swab Collection System (T583)

Specimen Volume: Swab

Collection Instructions:

1. Swab site using Aptima Collection Multitest Swab (T584) or Aptima Collection Unisex Swab (T583).

Note: The white swab provided within the collection kit is a cleaning swab and should not be used for collection. Discard the white cleaning swab.

2. Place swab in transport tube provided in collection kit. Snap off swab at score line so swab fits into closed tube.

3. Cap tube securely, and label tube with patient's entire name, and date and time of collection.

4. Transport swab container to laboratory and store (refrigerated is preferred) within 60 days of collection.

 

Supplies: Aptima Thin Prep Transport Tube (T652)

Specimen Type: Peritoneal fluid (pelvic wash, cul-de-sac fluid)

Container/Tube: Aptima Specimen Transfer Tube (T652)

Specimen Volume: 1 mL

Collection Instructions:

1. Transfer 1 mL of specimen into the Aptima Specimen Transfer Tube (T652) within 24 hours of collection.

2. Cap tube securely, and label tube with patient's entire name, and date and time of collection.

3. Transport Aptima Specimen Transfer Tube to laboratory (refrigerated is preferred) within 30 days of collection.


Specimen Minimum Volume

Oral/Throat, Ocular, Anal/Rectal Swabs: Entire collection
Peritoneal Fluid: 1 mL

Specimen Stability Information

Specimen Type Temperature Time
Varies Refrigerated (preferred)
  Ambient 
  Frozen 

Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

Sources other than those listed above.

Reference Values

Negative

Day(s) and Time(s) Performed

Monday through Saturday; Varies

CPT Code Information

87591

LOINC Code Information

Test ID Test Order Name Order LOINC Value
MGRNA N. gonorr, Misc, Amplified RNA 43305-2

 

Result ID Test Result Name Result LOINC Value
SRC22 SOURCE: 31208-2
34508 N. gonorr, Misc, Amplified RNA 43305-2

Analytic Time

1 day

Cautions

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

-Lubricants and spermicides

Method Description

The Hologic Aptima Combo 2 Assay combines the technologies of target capture, transcription-mediated amplification, and dual kinetic assay. The detection of the rRNA amplification product sequences (amplicon) is achieved using nucleic acid hybridization. Single-stranded Chemiluminescent DNA probes are labeled and combine with amplicon to form stable RNA:DNA hybrids. Light emitted from the labeled RNA:DNA hybrids is measured as photon signals in a luminometer.(Package insert: Hologic APTIMA Combo 2 Assay 502487 Rev 1)

Interpretation

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.

Specimen Retention Time

7 days

Clinical Information

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 N gonorrhoeae detection, but these methods are significantly less sensitive and less specific than NAAT.(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.

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

Supportive Data

Accuracy/Diagnostic Sensitivity and Specificity

 

Accuracy:

 

1. Clinical Specimens

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


*Additional studies using raw peritoneal fluid in lieu of swab collection were performed for a more concise specimen collection and enhanced recovery. One mL of peritoneal fluid was added to a GenProbe APTIMA specimen transfer kit then spiked with Chlamydia trachomatis and N gonorrhoeae at the limit of detection.

 

Source

Positives

CT IFU/assay

NG CFU/assay

Concordance

Peritoneal Fluid

20

3

50

100%

IFU - inclusion forming units

 

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

Positives (Number tested)

Negatives (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 Hologic (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(colony forming units)/assay. 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 Hologic (GEN-PROBE) as outlined in the APTIMA product insert, an additional panel was tested by the Tigris DTS System using the APTIMA COMBO 2 Assay. Analyte-negative patient specimens collected in Hologic 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.