Evaluation of Gonorrhea Screening in Family Planning

Settings: California 2000

CK Kent, M Brammeier, G Bolan, N Casas,

M Funabiku, P Blackburn

Region IX Infertility Prevention Project

Background

• No comprehensive gonorrhea screening guidelines• Median state-specific GC prevalence was 0.9%

– During 2000, among women 15-24 years seen in family planning settings (Poster 12)

• Most recent cost effectiveness study of GC screening – 1989– Screening cost-effective if prevalence >2.0%

Objective

• To evaluate gonorrhea screening of women in family planning settings in order to better target screening.

Data Sources

• Year 2000 data.

• 30 participating family planning clinics in California serving as sentinel screening sites.

• Examined gonorrhea (GC) & chlamydia (CT) test results, symptoms (Sx), age, & race/ethnicity.

Questions to Consider

• Prevalence of GC?

• How well do symptoms predict GC?

• How well does having CT predict GC?

• How well does having either symptoms OR CT predict GC?– Does this vary by age or race/ethnicity?

Test Results

• 93% of women tested for CT were also tested for GC.

• CT positive tests: 4.9% (1,497/30,568)

• GC positive tests: 0.9% (257/28,590)

How does GC prevalence vary by sites?

• Range of prevalence: 0.0% - 2.5%

• Two of 30 (6.9%) sites had prevalence greater than 2%

Proportion of GC positive tests among women by predictors of GC

0.9%1.7%

0.6%

6.2%

0.6%1.3%

0.5%

2.5%

0.5%

0%

2%

4%

6%

8%

Ove

rall Sx

No Sx

CT

No CT

< 25 y

25+

Black

Not B

lack

GC +

How does having either symptoms or CT affect GC status?

Proportion of GC positive tests among women by symptom/CT status

0%

1%

2%

3%

4%

No Sx/CT Sx/CT

GC +

0.5%

2.1%

N=21,324 N=7,266

Proportion of GC positive tests is 2.5 times higher in

younger women.

How does this vary by symptoms/CT status?

% of GC positive tests among women by symptom/CT status & age

1.5%

0.7%

4.1%

0.5%

2.3%

0.4% 0.3%

1.0%1.0%

0%

1%

2%

3%

4%

5%

Total No Sx/CT Sx/CT

GC +

<20 yrs 20-24 yrs 25+ yrs

African Americans have 5 times higher prevalence of GC than

other race/ethnicities

How does this vary by symptoms/CT status?

% of GC positive tests among women by symptom/CT status & race/ethnicity

2.5%

1.1%

4.3%

0.5%0.3%

1.0%

0%

1%

2%

3%

4%

5%

Total No Sx/CT Sx/CT

GC + BlackAll others

The proportion of women with either symptoms or chlamydia among all women tested

25%

75%

No Sx/CT Sx/CT

N=28,590

Given these low prevalences of GC, what are the consequences?

Positive Predictive Value (PPV) & Observed Prevalence by True Prevalence in Population Assuming Tests with a

Sensitivity of 95% & Specificities of 99.0% or 99.5%

Specificity 99.0% Specificity 99.5%

True Prevalence

PPV Observed Prevalence

PPV Observed Prevalence

0% 0% 1.0% 0% 0.5%

0.5% 33% 1.5% 50% 1.0%

1.0% 50% 2.0% 66% 1.5%

2.0% 66% 2.9% 79% 2.4%

5.0% 83% 5.8% 91% 5.3%

(Note: see poster 79 for more details)

Potential Human Costsof False Positives

• Unnecessary treatment

• Lost time/expense for follow-up visit

• Damaged relationships

• Increased risk of domestic violence (particularly if partner is negative)

PPV* of observed GC prevalence compared to observed CT prevalence in

CA Family Planning Data: 2000Factor %+ PPV GC Total tested 0.9% 44% No Sx/CT 0.5% 0% Sx/CT 2.1% 76% CT Total tested 4.9% 90% *Assuming 95% sensitivity & 99.5% specificity

Potential Fiscal Impact of GC testing on California Family Pact

• Assume 600,000 GC tests billed & 50% were amplified tests.

• $19,800,000 reimbursed for GC testing.

• Costs will increase as more providers and laboratories switch to amplified testing.

Summary

• Prevalence of GC among women screened in family planning settings in California very low (0.9%).

• If tests being used for GC screening are 99.5% specific, approximately 50% of test positives are false positives. Much higher false positive rate if tests are less specific.

Summary Con’t

• If perform only diagnostic GC testing among women with symptoms or CT, reduce testing by 75%.

• Substantial resources are being devoted to GC screening in California that could potentially be used for other public health purposes.

Recommendations

• If continue testing at current prevalence, confirmatory testing should be considered

• San Francisco– Discontinue screening in sites with a GC prevalence of

<2%.

– Perform diagnostic testing based on signs/symptoms and result of CT test on women <35 years.

• Cost effectiveness studies are needed

Fiscal Impact of GC testing on Family Pact: Fiscal Year 1999-2000

• 613,000 GC tests billed (52% were amplified tests).

• $20,000,000 reimbursed for all GC testing.

• About 90% of women who are tested for CT are also tested for GC.

• 58% increase in laboratory costs due to switch to amplified testing for CT & GC.