Evaluating Efforts to Increase Testing for Repeat Chlamydia Infection Among Women in California Family Planning Clinics

1. Evaluating Efforts to Increase Testing for Repeat Chlamydia Infection Among Women in California Family Planning Clinics Renee Gindi1, Heidi Bauer2, Joan Chow2, Melanie Deal1 1 California Family Health Council, Berkeley, CA 2 California Sexually Transmitted Disease Control Branch, Berkeley, CA I would like to thank my co-authors, Heidi Bauer and Joan Chow at the California State Dept of Health Services STD Control Branch, and Melanie Deal at the California Family Health Council for their contribution to this work.I would like to thank my co-authors, Heidi Bauer and Joan Chow at the California State Dept of Health Services STD Control Branch, and Melanie Deal at the California Family Health Council for their contribution to this work.

2. Background Repeat chlamydial infection can lead to increased risk of sequelae Studies estimate that >10% of women with chlamydia are re-infected within 4 months Most repeat infections are due to re-infection from untreated partner CDC Guidelines Clinicians should consider advising all [non-pregnant] women with chlamydial infection to be re-screened 3-4 months after treatment. Chlamydia trachomatis is the most commonly reported infectious disease in the United States, and when left untreated, can cause pelvic inflammatory disease and infertility. Some studies have suggested that repeat infection can lead to increases risk of these sequelae. Most studies estimate that more than 10% of chlamydia cases are re-infected within 4 months. Most repeat infection is re-infection through sex with an untreated partner. In May of 2002, the CDC released the latest STD treatment guidelines, recommending that clinicians consider re-screening non-pregnant women with chlamydia 3-4 months after treatment. Because most chalmydial infections are asymptomatic in women, repeat infections are most likely to be detected by screening, not diagnostic testing. (I’ll be using the term “re-screening” to refer to screening for repeat infection.) Notes for Possible Q&A: 1. Animal models / immunological studies are the basis of the assertion that repeat infection can lead to increased risk of sequelae. 2. Noncompliance with treatment may also be an issue with repeat infection. Treatment data not collected for this study. 3. CA guidelines reflect the CDC guidance in the California Chlamydia Action Coalition and Region IX IPP Clinical Guidelines. 4. Guidelines for pregnant women differ because CDC recommended medication regimens include less efficacious treatments. Pregnant women using these treatments are advised to be re-screened in 3 weeks. 5. In my review of the literature, studies ranged widely in both estimates of repeat infection (~8% to 33%) but also in the time periods at which they measured repeat infection. The “>10%” statistic is based on a review of re-screening by Matthew Golden at UW.Chlamydia trachomatis is the most commonly reported infectious disease in the United States, and when left untreated, can cause pelvic inflammatory disease and infertility. Some studies have suggested that repeat infection can lead to increases risk of these sequelae. Most studies estimate that more than 10% of chlamydia cases are re-infected within 4 months. Most repeat infection is re-infection through sex with an untreated partner. In May of 2002, the CDC released the latest STD treatment guidelines, recommending that clinicians consider re-screening non-pregnant women with chlamydia 3-4 months after treatment. Because most chalmydial infections are asymptomatic in women, repeat infections are most likely to be detected by screening, not diagnostic testing. (I’ll be using the term “re-screening” to refer to screening for repeat infection.) Notes for Possible Q&A: 1. Animal models / immunological studies are the basis of the assertion that repeat infection can lead to increased risk of sequelae. 2. Noncompliance with treatment may also be an issue with repeat infection. Treatment data not collected for this study. 3. CA guidelines reflect the CDC guidance in the California Chlamydia Action Coalition and Region IX IPP Clinical Guidelines. 4. Guidelines for pregnant women differ because CDC recommended medication regimens include less efficacious treatments. Pregnant women using these treatments are advised to be re-screened in 3 weeks. 5. In my review of the literature, studies ranged widely in both estimates of repeat infection (~8% to 33%) but also in the time periods at which they measured repeat infection. The “>10%” statistic is based on a review of re-screening by Matthew Golden at UW.

3. Study Objectives Estimate the baseline re-screening rate in selected California family planning clinics Promote the CDC guidelines and re-screening recommendations to family planning clinic staff Evaluate re-screening rates before and after the release of the CDC guidelines Primarily, this evaluation estimates the adherence to the CDC recommendations around re-screening. To do this, we established the baseline re-screening rate before the release of the CDC guidelines in selected family planning clinics. Next, we promoted the guidelines and the re-screening recommendations to the staff at California family planning clinics. Finally, we evaluated the re-screening rates at select family planning clinics before and after the release of the guidelines.Primarily, this evaluation estimates the adherence to the CDC recommendations around re-screening. To do this, we established the baseline re-screening rate before the release of the CDC guidelines in selected family planning clinics. Next, we promoted the guidelines and the re-screening recommendations to the staff at California family planning clinics. Finally, we evaluated the re-screening rates at select family planning clinics before and after the release of the guidelines.

4. Methods: Data Line-listed chlamydia test data from 1999-2003 at 13 family planning clinics Defining “re-screening” Second test between 3-4 months Second test between 1-6 months Excludes: Males Initial positive tests after July 1, 2003 Cases re-screened within 30 days Statistical analysis Trends Grouped by pre/post-guidelines release Line-listed chlamydia test data were collected from 1999-2003 at 13 Title X-funded California family planning clinics. According to the CDC Guidelines, re-screening is recommended between 3-4 months following treatment. For the purposes of this analysis, re-screening is defined as having a second test between 3-4 months after the initial positive test. A broader definition that might be more clinically practical is a second test between 1-6 months after the initial positive test. CDC guidelines do not make recommendations regarding re-screening of males, so males were excluded from this analysis. The broader definition of re-screening (2nd test between 1-6 months) requires that each woman have at least 6 months of possible follow-up time. Data were collected through December 2003, so women without at least 6 months of potential follow-up, whose first positive test was after July 1, 2003 were excluded. Women re-screened within 30 days of their initial positive test were excluded from trend analyses. We analyzed trends in re-screening rates between 1999 and 2003. We also restricted the time frame of the analysis to the 12 months before and after the guidelines’ release, to look at trends and grouped analyses. We also stratified results by age group. Line-listed chlamydia test data were collected from 1999-2003 at 13 Title X-funded California family planning clinics. According to the CDC Guidelines, re-screening is recommended between 3-4 months following treatment. For the purposes of this analysis, re-screening is defined as having a second test between 3-4 months after the initial positive test. A broader definition that might be more clinically practical is a second test between 1-6 months after the initial positive test. CDC guidelines do not make recommendations regarding re-screening of males, so males were excluded from this analysis. The broader definition of re-screening (2nd test between 1-6 months) requires that each woman have at least 6 months of possible follow-up time. Data were collected through December 2003, so women without at least 6 months of potential follow-up, whose first positive test was after July 1, 2003 were excluded. Women re-screened within 30 days of their initial positive test were excluded from trend analyses. We analyzed trends in re-screening rates between 1999 and 2003. We also restricted the time frame of the analysis to the 12 months before and after the guidelines’ release, to look at trends and grouped analyses. We also stratified results by age group.

5. Methods: Guideline Promotion May 2002: CDC STD Treatment Guidelines released May 2002: CFHC e-mail to 250 clinics June 2002: CIPP memo to 250 clinics Nov 2002: guidance document distribution to 19 agencies at conference Apr 2003: guidance document distribution to 31 agencies at conference In yellow are the events that promoted the entire CDC STD Treatment Guidelines document. In blue are the events that promoted additional guidance documents based on the CDC Guidelines. In May 2002, the CDC STD Treatment Guidelines were released. That same month, the California Family Health Council, the agency that administers the Title X family planning grant in California promoted the CDC STD Treatment Guidelines in an e-mail that went out to providers and staff at over 250 clinics. In June 2002, the California State Infertility Prevention Project (CIPP), a part of the CDC-sponsored chlamydia prevalence monitoring project in partnership with CFHC, sent a memo to these same clinics regarding the release of the new guidelines, encouraging clinics to keep a copy of the new guidelines as reference for their clinical protocols. The CDC Treatment Guidelines, and the California Chlamydia Action Coalition (CCAC) chlamydia guidelineswere distributed at conferences in November 2002 and April 2003. Not all of the clinics evaluated were represented at these conferences In yellow are the events that promoted the entire CDC STD Treatment Guidelines document. In blue are the events that promoted additional guidance documents based on the CDC Guidelines. In May 2002, the CDC STD Treatment Guidelines were released. That same month, the California Family Health Council, the agency that administers the Title X family planning grant in California promoted the CDC STD Treatment Guidelines in an e-mail that went out to providers and staff at over 250 clinics. In June 2002, the California State Infertility Prevention Project (CIPP), a part of the CDC-sponsored chlamydia prevalence monitoring project in partnership with CFHC, sent a memo to these same clinics regarding the release of the new guidelines, encouraging clinics to keep a copy of the new guidelines as reference for their clinical protocols. The CDC Treatment Guidelines, and the California Chlamydia Action Coalition (CCAC) chlamydia guidelineswere distributed at conferences in November 2002 and April 2003. Not all of the clinics evaluated were represented at these conferences

6. Results: Study Population 64,652 chlamydia tests were done on women attending family planning clinics between Jan 1999-Jun 2003. Of these tests, 3,149 were positive, (positivity 4.8%). These 3,149 positive results represented 2,953 unique women with a positive test. Of these women, 50% (n=1282) had a second chlamydia during the entire data collection period, but only 22% (n=651) had that second chlamydia test within 1-6 months. 4.5% (134 clients) had their second test between 3-4 months. Consistent with other studies, of those re-screened within 6 months, 11% (74 clients) had a second positive test. Notes for Possible Q&A: Positivity in this population varied from 4.3% to 5.4% during the 5 years studied. 81% of the women with a positive test were <25 (n=2367). 50% of the women with a positive test were tested between July 2001-Jun 2003 (n=1496). Less than 2%, or 47 clients, had a test of cure. 32%, or 15, of these clients had another test within 1-6 months of the test of cure. 13%, or 6, had another test within 3-4 months of the test of cure.64,652 chlamydia tests were done on women attending family planning clinics between Jan 1999-Jun 2003. Of these tests, 3,149 were positive, (positivity 4.8%). These 3,149 positive results represented 2,953 unique women with a positive test. Of these women, 50% (n=1282) had a second chlamydia during the entire data collection period, but only 22% (n=651) had that second chlamydia test within 1-6 months. 4.5% (134 clients) had their second test between 3-4 months. Consistent with other studies, of those re-screened within 6 months, 11% (74 clients) had a second positive test. Notes for Possible Q&A: Positivity in this population varied from 4.3% to 5.4% during the 5 years studied. 81% of the women with a positive test were <25 (n=2367). 50% of the women with a positive test were tested between July 2001-Jun 2003 (n=1496). Less than 2%, or 47 clients, had a test of cure. 32%, or 15, of these clients had another test within 1-6 months of the test of cure. 13%, or 6, had another test within 3-4 months of the test of cure.

7. Rates of re-screening within 3-4 months Overall, rates of re-screening within 3-4 months ranged from a low of 3.7% (1999H1, 1999H2, 2002H1) to a high of 6.2% (2003H1). The arrows represent the different points of guideline promotion in May, June, and November of 2002, and April of 2003. <<click – dotted lines appear>> When we restricted the trend analysis to cases found between July 2001 and Jun 2003 (the twelve months before and after the guidelines’ release), the rate of re-screening increases from 3.7% to 6.2%. This change only approaches significance (p=0.06). <<click – heavy dashed line appears>> If cases are grouped by before and after guidelines’ release, then cases are significantly more likely to be re-screened within 3-4 months after the release of the guidelines (p=0.03). We also looked at re-screening rates stratified by age. Among women under 25, both the trend and the grouped comparisons showed a significant increase in rates of re-screening within 3-4 months, increasing from 3.04% to 6.46% re-screened within 3-4 months. Among women 25 and over, neither comparison was significant, but that may be attributable to the small number of women in this class. The rates of re-screening within 3-4 months of a positive test are increasing, but how is this change reflected in the more clinically practical definition of re-screening within 1-6 months? Overall, rates of re-screening within 3-4 months ranged from a low of 3.7% (1999H1, 1999H2, 2002H1) to a high of 6.2% (2003H1). The arrows represent the different points of guideline promotion in May, June, and November of 2002, and April of 2003. <<click – dotted lines appear>> When we restricted the trend analysis to cases found between July 2001 and Jun 2003 (the twelve months before and after the guidelines’ release), the rate of re-screening increases from 3.7% to 6.2%. This change only approaches significance (p=0.06). <<click – heavy dashed line appears>> If cases are grouped by before and after guidelines’ release, then cases are significantly more likely to be re-screened within 3-4 months after the release of the guidelines (p=0.03). We also looked at re-screening rates stratified by age. Among women under 25, both the trend and the grouped comparisons showed a significant increase in rates of re-screening within 3-4 months, increasing from 3.04% to 6.46% re-screened within 3-4 months. Among women 25 and over, neither comparison was significant, but that may be attributable to the small number of women in this class. The rates of re-screening within 3-4 months of a positive test are increasing, but how is this change reflected in the more clinically practical definition of re-screening within 1-6 months?

8. Rates of re-screening within 1-6 months When we looked at the rates of re-screening within 1-6 months by half-year (similar to the previous slide), the resulting graph did not lend itself well to trend analysis. To smooth out the curve, we instead looked at the rates by year. Because the CDC Guidelines were released in the middle of calendar year 2002, we decided to look at 12 month periods rather than calendar years. Overall, rates of re-screening within 1-6 months ranged from 20 to 26 percent. <<click – dashed lines appear>> When we restricted the analysis to cases found between May 2001 and May 2003, the rate of re-screening increases, but not significantly (p=0.08). Overall, it seems that while re-screening within the CDC-recommended timeframe of 3-4 months is increasing, re-screening rates according to a “clinically practical” definition have stayed level.When we looked at the rates of re-screening within 1-6 months by half-year (similar to the previous slide), the resulting graph did not lend itself well to trend analysis. To smooth out the curve, we instead looked at the rates by year. Because the CDC Guidelines were released in the middle of calendar year 2002, we decided to look at 12 month periods rather than calendar years. Overall, rates of re-screening within 1-6 months ranged from 20 to 26 percent. <<click – dashed lines appear>> When we restricted the analysis to cases found between May 2001 and May 2003, the rate of re-screening increases, but not significantly (p=0.08). Overall, it seems that while re-screening within the CDC-recommended timeframe of 3-4 months is increasing, re-screening rates according to a “clinically practical” definition have stayed level.

9. Distribution of time to re-screen among those re-screened within 6 months The proportion of cases screened within 6 months has not changed significantly over time. What we’re seeing is a shift from re-screening earlier (less than 2 months) to later (between 3 and 6 months). The proportion of cases screened within 6 months has not changed significantly over time. What we’re seeing is a shift from re-screening earlier (less than 2 months) to later (between 3 and 6 months).

10. Distribution of time to re-screen among those re-screened within 6 months Out of those cases re-screened within 6 months, the relative proportion of cases re-screened within 3-4 months has been increasing (from 14% in 1999H2 to 25% in 2003H1). (Also hits 24% in 2001H1.) Out of those cases re-screened within 6 months, the relative proportion of cases re-screened within 3-4 months has been increasing (from 14% in 1999H2 to 25% in 2003H1). (Also hits 24% in 2001H1.)

11. Median time to re-screen among those re-screened within 6 months Another way to show this shift from earlier to later re-screening is to look at the median time to re-screening among those re-screened within 6 months. <<click – text boxes and line appear>> Before the guidelines’ release, the median time to re-screen was 76 days. After the guidelines’ release, the median was 90 days.Another way to show this shift from earlier to later re-screening is to look at the median time to re-screening among those re-screened within 6 months. <<click – text boxes and line appear>> Before the guidelines’ release, the median time to re-screen was 76 days. After the guidelines’ release, the median was 90 days.

12. Discussion Overall rates of re-screening remain low 4.5% within 3-4 months 22% within 1-6 months Increase in re-screening between 3-4 months Statistical significance varied based on mode of analysis Guideline promotion may have lengthened the time to re-screening Rates of re-screening according to the CDC guidelines’ recommendations remain low through 2003. 4.5% of cases were re-screening within 3-4 months, and 22% of cases were re-screened within 1-6 months. Distribution and promotion of the guidelines does not seem sufficient to increase rates of re-screening overall. There was an increase in the rate of re-screening between 3-4 months. The statistical significance of the increase varied based on the mode of analysis. More likely, the effect of the guidelines’ promotion was to lengthen the time to re-screening from less than 3 months to more than 3 months. Rates of re-screening according to the CDC guidelines’ recommendations remain low through 2003. 4.5% of cases were re-screening within 3-4 months, and 22% of cases were re-screened within 1-6 months. Distribution and promotion of the guidelines does not seem sufficient to increase rates of re-screening overall. There was an increase in the rate of re-screening between 3-4 months. The statistical significance of the increase varied based on the mode of analysis. More likely, the effect of the guidelines’ promotion was to lengthen the time to re-screening from less than 3 months to more than 3 months.

13. Limitations: Data Secondary data Did not collect “chlamydia re-test” as reason for visit Test date used as approximation for treatment date Short observational period 12 months after CDC guidelines released Data from LA and SF not included There were some limitations to the data used in this evaluation. We used secondary data sources to evaluate the rates of re-screening, and did not ask whether a woman had specifically returned for a chlamydia re-test at that visit. That information would have allowed us to differentiate between a woman returning for a re-screen and a woman being re-tested during a contraceptive supply visit, like receiving a Depo shot or oral contraceptive refill. Given that the rates of Depo and oral contraceptive were relatively stable between 2001-2003, it’s unlikely that any changes in re-screening rates were due to changes in contraceptive method use. (See slide 19 for more) Test date was used as an approximation for treatment date, which may bias re-screening rates downward. With such a short observational period, this is only a first look at provider behavior. New guideline adoption by providers can often be slow, and adherence would not be expected to increase within the first 12 months after the CDC guidelines were released. Los Angeles county and San Francisco county prevalence monitoring data were not included in this analysis, so the results are representative of the California Project Area only. Other limitations: No direct provider data Multiple points of guideline promotion make it difficult/impossible to evaluate the effects of individual types of promotion FPACT pays for tests, so this evaluation may be applicable only in CA / Medicaid populations There were some limitations to the data used in this evaluation. We used secondary data sources to evaluate the rates of re-screening, and did not ask whether a woman had specifically returned for a chlamydia re-test at that visit. That information would have allowed us to differentiate between a woman returning for a re-screen and a woman being re-tested during a contraceptive supply visit, like receiving a Depo shot or oral contraceptive refill. Given that the rates of Depo and oral contraceptive were relatively stable between 2001-2003, it’s unlikely that any changes in re-screening rates were due to changes in contraceptive method use. (See slide 19 for more) Test date was used as an approximation for treatment date, which may bias re-screening rates downward. With such a short observational period, this is only a first look at provider behavior. New guideline adoption by providers can often be slow, and adherence would not be expected to increase within the first 12 months after the CDC guidelines were released. Los Angeles county and San Francisco county prevalence monitoring data were not included in this analysis, so the results are representative of the California Project Area only. Other limitations: No direct provider data Multiple points of guideline promotion make it difficult/impossible to evaluate the effects of individual types of promotion FPACT pays for tests, so this evaluation may be applicable only in CA / Medicaid populations

14. Limitations: Intervention Distributed entire CDC STD Treatment Guidelines document Targeted guidance documents highlighted other chlamydia screening practices in addition to re-screening The intervention itself was imprecise (?). The entire (80 page) CDC STD Treatment Guidelines document was initially distributed to clinics. And when we distributed targeted guidance documents that focused solely on the Guidelines’ chlamydia screening messages, these focused documents highlighted other chlamydia screening practices in addition to re-screening. Given that the distribution and promotion of guidelines is not sufficient to increase rates of re-screening overall, and we need to evaluate additional methods for their effectiveness in increasing rates of re-screening. The intervention itself was imprecise (?). The entire (80 page) CDC STD Treatment Guidelines document was initially distributed to clinics. And when we distributed targeted guidance documents that focused solely on the Guidelines’ chlamydia screening messages, these focused documents highlighted other chlamydia screening practices in addition to re-screening. Given that the distribution and promotion of guidelines is not sufficient to increase rates of re-screening overall, and we need to evaluate additional methods for their effectiveness in increasing rates of re-screening.

15. Next Steps Performance measures for providers and clinics Give feedback to providers and clinics Eliminate financial barriers to re-screening Educate clients about risks of re-infection Make re-screening more convenient for clients Increase emphasis on partner management There are a variety of approaches that may help to increase rates of re-screening: Performance measures for providers and clinics can be used to monitor quality of care by measuring rates of re-screening. During CFHC federal audits of Title X agencies, we look at the rate of re-screening among a small sample of charts of chlamydia positive clients. We provide feedback to the providers and clinics based on whether re-screening is documented in the charts. Financial barriers to re-screening can be eliminated by ensuring that all eligible clients are enrolled in Family PACT, a statewide reproductive health entitlement program, or other entitlement programs that will pay for testing. In addition, having “express visits” or non-clinician personnel doing testing may reduce provider time spent on re-screening and be cost-saving to clinics. Educating clients about the risks of re-infection and making re-screening more convenient may increase client willingness to be re-screened. We are currently collaborating on a project to evaluate the effect of mailed self-collected vaginal swab kits on re-screening rates. The ultimate goal is really to increase emphasis on partner management and partner treatment, reduce repeat infection, and eventually reduce the need for re-screening. Notes: Family PACT enrollment is documented for 31% of positive clients (939/2953). Of FPACT clients, 59.7% did not return for a second test. Of non-FPACT documented clients, 55% did not return for a second test.There are a variety of approaches that may help to increase rates of re-screening: Performance measures for providers and clinics can be used to monitor quality of care by measuring rates of re-screening. During CFHC federal audits of Title X agencies, we look at the rate of re-screening among a small sample of charts of chlamydia positive clients. We provide feedback to the providers and clinics based on whether re-screening is documented in the charts. Financial barriers to re-screening can be eliminated by ensuring that all eligible clients are enrolled in Family PACT, a statewide reproductive health entitlement program, or other entitlement programs that will pay for testing. In addition, having “express visits” or non-clinician personnel doing testing may reduce provider time spent on re-screening and be cost-saving to clinics. Educating clients about the risks of re-infection and making re-screening more convenient may increase client willingness to be re-screened. We are currently collaborating on a project to evaluate the effect of mailed self-collected vaginal swab kits on re-screening rates. The ultimate goal is really to increase emphasis on partner management and partner treatment, reduce repeat infection, and eventually reduce the need for re-screening. Notes: Family PACT enrollment is documented for 31% of positive clients (939/2953). Of FPACT clients, 59.7% did not return for a second test. Of non-FPACT documented clients, 55% did not return for a second test.

16. Thank you very much for your time. I can now (?) take questions.Thank you very much for your time. I can now (?) take questions.

17. Additional Materials

18. Repeat infection rates There is no clear trend in rates of repeat infection either overall, or when stratified by age group. Rates of repeat infection varied between 6.9% to 16%. Repeat infection rates likely change based on the amount of re-screening and chlamydia test performance. There is no clear trend in rates of repeat infection either overall, or when stratified by age group. Rates of repeat infection varied between 6.9% to 16%. Repeat infection rates likely change based on the amount of re-screening and chlamydia test performance.

19. Rates of select contraceptive method use Overall, levels of depo-provera (requires clinic visit every 3 months) have remained stable and low. Levels of OCP use have risen, and may, but don’t necessarily require a clinic visit every 3-4 months.Overall, levels of depo-provera (requires clinic visit every 3 months) have remained stable and low. Levels of OCP use have risen, and may, but don’t necessarily require a clinic visit every 3-4 months.

20. Rates of re-screening within 1-6 monthsby half-year Overall, rates of re-screening within 1-6 months ranged from 14% (2001H1) to 27% (2000H1). The arrows represent the different points of guideline promotion in May, June, and September of 2002, and April of 2003. A chi-squared test for trend showed no overall trend in the rate of re-screening within 1-6 months (p=0.41)Overall, rates of re-screening within 1-6 months ranged from 14% (2001H1) to 27% (2000H1). The arrows represent the different points of guideline promotion in May, June, and September of 2002, and April of 2003. A chi-squared test for trend showed no overall trend in the rate of re-screening within 1-6 months (p=0.41)

21. Rates of Test of Cure Recommendations around Test of Cure (second test with 30 days) were also a part of the CDC guidelines. From this graph, we can see that even when they were most common, tests of cure were rarely done among all cases (less than 5%). However, in late 2000-early 2001, TOC accounted for almost 20% of all re-tests done within 6 months of the positive test. This proportion has decreased since 2001, and is currently 3.8% of all re-tests done within 6 months.Recommendations around Test of Cure (second test with 30 days) were also a part of the CDC guidelines. From this graph, we can see that even when they were most common, tests of cure were rarely done among all cases (less than 5%). However, in late 2000-early 2001, TOC accounted for almost 20% of all re-tests done within 6 months of the positive test. This proportion has decreased since 2001, and is currently 3.8% of all re-tests done within 6 months.