# Presentation: 184417

## Confirmatory Testing of NAATs SHOULD be Routine for Chlamydia Infections in Populations with < 4% Prevalence

- Harold C. Wiesenfeld, M.D.,C.M.
- University of Pittsburgh School of Medicine
- Magee-Womens Hospital

## Positive Predictive Value:The Influence of Disease Prevalence

- Zenilman. Sex Transm Infect 2003

## Positive Predictive Value:The Influence of Disease Prevalence

|  | PPV at Specificity of: |  |  |
| --- | --- | --- | --- |
| Prevalence | 98%  | 99% | 99.5% |
| 10% | 84% | 91% | 95% |
| 5% | 71% | 83% | 90% |
| 2% | 49% | 66% | 79% |
| 1% | 32% | 49% | 66% |
| 0.5% | 19% | 32% | 49% |

## Positive Predictive Value:The Influence of Disease Prevalence95% Sensitivity  99% Specificity

| Prevalence | Test | True Infection |  |  | PPV |
| --- | --- | --- | --- | --- | --- |
|  |  | + | - |  |  |
| 10% | + | 95 | 9 | 104 | 91% |
|  | - | 5 | 891 | 896 | (95/104) |
|  |  | 100 | 900 | 1000 |  |
| 4% | + | 38 | 10 | 48 | 79% |
|  | - | 2 | 950 | 952 | (38/48) |
|  |  | 40 | 960 | 1000 |  |
| 2% | + | 19 | 10 | 29 | 66% |
|  | - | 1 | 970 | 971 | (19/29) |
|  |  | 20 | 980 | 1000 |  |

## BD ProbeTec PerformanceMulticenter Evaluation

|  |  | Female Swab |  | Male Swab |  |
| --- | --- | --- | --- | --- | --- |
| Lab | Prevalence | SPEC | PPV | SPEC | PPV |
| IU | 13.4% | 95.7 | 76.8 | 96.1 | 86.8 |
| JHU | 9.0% | 99.0 | 87.4 | 98.1 | 92.1 |
| UCSF | 5.3% | 100 | 100 | 100 | 100 |
| SJPHS | 4.4% | 99.2 | 84.6 | - | - |
| UAB | 15.1% | 98.6 | 92.1 | 95.2 | 86.3 |
| UMMS | 10.9% | 98.6 | 77.7 | 80.0 | 50 |
| CCF | 11.5% | 95.7 | 75.1 | - | - |

- Van Der Pol et al. J Clin Micro 2001

## LCR PerformanceMulticenter Evaluation

|  |  | Female Swab |  | Male Urine |  |
| --- | --- | --- | --- | --- | --- |
| Lab | Prevalence | SPEC | PPV | SPEC | PPV |
| IU | 13.4% | 98.8 | 92.5 | 97.0 | 89 |
| JHU | 9.0% | 99.0 | 85.6 | 96.2 | 85.4 |
| UCSF | 5.3% | 100 | 100 | 100 | 100 |
| SJPHS | 4.4% | 99.4 | 88.5 | - | - |
| UAB | 15.1% | 99.3 | 95.9 | 95.2 | 97.3 |
| UMMS | 10.9% | 98.5 | 89.1 | 80.0 | 66.7 |
| CCF | 11.5% | 100 | 100 | - | - |

- Van Der Pol et al. J Clin Micro 2001

## Reproducibility of BD Probe-Tec

|  | Initial MOTA Scores |  |
| --- | --- | --- |
|  | 2,000-9,999 | >10,000 |
| Repeat Positive | 21 | 175 |
| Repeat Negative | 5 | 6 |
| Total | 26 | 181 |

- Culler. J Clin Micro 2003

## Implications of a Positive CT Test

- Psychosocial Impact/Stigma
- Negative impact on sexual relationships
- Future Reproductive Morbidity
- Cost
- Resource Utilization

## Implications of a Positive CT Test

- Psychosocial Impact
- Shock
- Depression
- Anxiety
- Guilt
- Isolation
- Shame
- Stigma (?barrier to future STD care?)

## Implications of a Positive CT Test

- Negative impact on sexual relationships
- Destroyed relationships
- Accusations of infidelity
- Impaired intimacy
- Less sexually desirable
- Less sexual enjoyment

## Implications of a Positive CT Test

- Future Reproductive Morbidity
- Increased risk of
- Ectopic pregnancy
- Tubal factor infertility
- Chronic pelvic pain
- Neonatal transmission

## Implications of a False-Positive CT TestShort-Term Costs

_**Confirmatory Testing**_
- Additional assay
- Small # of specimens in low prev. populations
- Lab issues

_**No Confirmatory Testing**_
- Treatment
- Partner notification
- Partner treatment
- Screening for other STDs
- Counseling time

## Implications of a Positive CT TestLong-Term Costs

- _Resource Utilization_
- False positive tests will lead to increased utilization of healthcare services ($$$)
- Repeat screening for *C. trachomatis*
- Follow national screening recommendations
- Increased healthcare utilization
- Patient is “labelled”
- All pelvic pain = PID (costs of treatment)
- Increased surveillance for ectopic pregnancy

## Implications of a False-Positive CT TestOverall Costs

_**Confirmatory Testing**_
- Additional assay

_**No Confirmatory Testing**_
- Treatment
- Partner notification
- Partner treatment
- Screening for other STDs
- Counseling time
- Repeat testing
- Future testing and work-up for possible STD-related illness (e.g. PID, ectopic pregnancy)

*Reduce costs*

## Is Educating Physicians on the Proper Interpretation
of STD Tests a
Viable Strategy?

- of STD Tests a
- Viable Strategy?

## Will Providers Properly Counsel Patients?

- 71% of PA primary care physicians report adequate STD training in residency (Ashton, Cook, Wiesenfeld et al. Sex Transm Dis 2002)
- 38% of adults were asked about STDs during routine checkups in the last year (Tao, Irwin & Kasler Am J Prev Med 2000)
- Only 32% of primary care physicians report screening a sexually active teen for CT (Cook, Wiesenfeld, Ashton et al. J Adol Health 2001)
- Only 61% of PCPs met criteria for adequate STD knowledge (Wiesenfeld, Cook et al. Unpublished data)
**	****QUALITY OF STD CARE VARIES AND IS IMPERFECT**

- 	“Clinicians must know the approximate prevalence of the condition of interest in the population being tested; if not, reasonable interpretation is impossible”
- David A. Grimes & Kenneth F. Shulz
*Uses and Abuses of Screening Tests*
- Lancet 2002

## What do the Providers Know About False Positive STD Tests?

- NOT MUCH!
- Survey of local providers:
_**94% underestimated**_ the false-positive rate of a NAAT CT test in a low prevalence population
- Most physicians vastly underestimated the false positive rate of CT NAAT testing:
_**Two-thirds**_ estimated the false positive rate of < 5% in a population where the risk of a positive test being a false positive is 50%

## Do Physicians Currently Follow Recommendations Concerning False-Positive Tests?

- CDC (MMWR Oct 18, 2002):
- “*Patients with positive screening test results require counseling regarding...the possibility of a false-positive result”*
- Survey:
- 	76% of physicians _**rarely**_ (<1%) inform patients with a positive CT NAAT result that it may be a false positive

## Do Physicians Currently Follow Recommendations Concerning False-Positive Tests?

- CDC (MMWR Oct 18, 2002):
*“**Because therapy for CT is safe and should not be delayed, therapy can be offered while awaiting additional test results...”*
- Survey:
- 	18% of physicians would offer empiric treatment before or in lieu of retesting

## Is Educating Physicians on the Proper Interpretation

- of STD Tests a
- Viable Strategy?
*Doubtful*

## Slide 22

## Should Confirmatory Testing of NAATs be Routine for Chlamydia Infections in Populationswith < 4% Prevalence?

- YES
- Not labor intensive
- Additional costs small (small #s)
- Reduction in costs incurred with false-positive tests (short and long-term)
- Eliminate unnecessary adverse psychosocial impact
- Feasibility of  providers incorporating counseling on false-positive results is questionable
**Improved quality of care for our patients**

- “	*Remember: a clinician, not a laboratory test, makes a diagnosis.  Overinterpretation of test results is the first cost of molecular diagnostics*”
- Jeffrey Klausner, MD
- Clin Infect Dis 2004