The house believes that positive GC NAAT results in low ...

1. The house believes that positive GC NAAT results in low prevalence populations should be confirmed.

3. NAAT Confirmation Approaches Second specimen, different gene target, different assay. Same specimen, different gene target, different assay. Repeat the original test with the same specimen. Same specimen, same assay, different gene target.

4. Documentation of False Positive GC NAAT Results in Hawaii Population prevalence: GC – 1.06%, CT – 4.13% Cases – 5 monogamous women 3 asymptomatic and 2 with BV. All reexamined and GC negative by TMA and culture. 4 partners examined and all negative for GC.

5. Documentation of False Positive GC NAAT Results in Hawaii Impact All women experienced emotional stress. One woman ended monogamous relationship. One severed long time relationship with care provider. Actions Note concerning possibility of FPs added to all GC positive reports. Web site to provide detailed information for clinicians. Letter from health department to all Hawaiian physicians concerning importance of sexual histories and explaining concept of PPV.

6. Positive Predictive Values

7. Gonorrhea — Positivity among 15-24 year old women tested in family planning clinics by 2000

8. CT and GC Prevalence in High School Girls

9. Why are we testing for GC in low prevalence populations? Manufactures offer bundled CT and GC assays together at a cost that is often no more than the cost of a CT assay alone. Up until recently third party payers have been reimbursing providers for each organism separately.

10. Variability in CT NAAT Results Between Testing Sites in the CDC 455 Study

11. Documentation of False Positive GC NAAT Results in a QA Project 96 laboratories participated; all NAAT systems represented. Three negative urines included in panel. One false positive result was reported for two of these by the different laboratories. Conclusion: Individual laboratory error resulted in FP rates of about 1%.

12. Lessons learned from Abbott Laboratory’s LCx assay experience.

13. COBAS AMPLICOR Gray Zone Phenomenon Gene target found in respiratory Neisseria species. False positives characterized by optical density (OD) readings of 0.2 to 3.5 (gray zone.) Initial results in the gray zone are repeated in duplicate. 2/3 results with ODs =2 are classified as positive. Specificity based on initial result ranged from 96.2 to 98.9. Retesting algorithm increased specificity to 98.5-99.9.

14. Reproducibility of 3 GC NAATs

15. Cost of Confirming Positive GC NAATs in Low Prevalence Populations 100 CT/GC assays at $14 each = $1,400. 3 GC confirmation assays at $16 each = $48. Total cost for screening and confirmation is $1,448, representing a 3.4% increase compared to screening alone.

16. Summary False positive NAAT test results are a fact of life even under optimal conditions. Such results have an adverse impact on patients. NAATs are complex; variation in individual laboratory performance is inevitable.

17. Summary NAAT kit manufacturing problems are always a possibility and not all NAATs perform the same. It follows from 3. and 4. that laboratories should have additional QA measures in place. Same assay, alternate target confirmation of positive GC NAAT results in low prevalence populations is not expensive.