Chlamydia Profiles, 2011
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This web page is archived for historical purposes and is no longer being updated. Newer data is available on the STD Data and Statistics page.
National Profile | Regional | State | City | Data Sources | Data Limitations
National Profile
• Figure A Data, National excluding outlying areas - Chlamydia rates among women, 2001-2011
• Figure B Data, National excluding outlying areas – Median state-specific mean chlamydia positivity among women aged 15-24 years, by testing site, 2001-2011
• Figure C Data, National excluding outlying areas - Median state-specific chlamydia positivity among women aged 15-24 years, by testing site, 2011
• Table 1 Data, National excluding outlying areas - Median state-specific chlamydia positivity among women tested in family planning clinics, by age group, 2011
The national profile provides summary information from US states, excluding outlying areas. The national profile on chlamydia trends contains three figures and one table.
Morbidity Surveillance: Reporting of Chlamydia Cases
Crude case rates (reported cases/population) were calculated on an annual basis per 100,000 population. Rates were calculated by dividing the number of cases reported nationally by the estimated population (the most current detailed population file available at time of publication).
Positivity in Screened Populations: Reporting of Chlamydia Positivity
Chlamydia test positivity was calculated by dividing the number of women testing positive for chlamydia (numerator) by the total number of women tested for chlamydia (denominator includes those with valid test results only and excludes unsatisfactory and indeterminate tests) and is expressed as a percentage. The denominator may contain multiple tests from the same individual if that person was tested more than once during the period for which screening data are reported. The numerator may also contain multiple positive test results from the same individual if that person tested positive more than once during the period for which screening data are reported. Various chlamydia laboratory methods were used and no adjustments of test positivity were made based on laboratory test type and sensitivity.
The number of clinics cited in Table 1 represents family planning (FP), sexually transmitted disease (STD), prenatal, and other clinics screening 25 or more women and juvenile and adult corrections facilities screening 100 or more women. To be included in Figure B, FP and STD clinics must have each had data on at least 50 tests in any given year and the National Job Training Program must have had data on 100 or more entrants in any given year. Each age group displayed in Figure C represents data on at least 100 tests within the past year.
Regional Profiles
•Figure A Data, All Regions - Chlamydia - Trends in Positivity Among Women Aged 15 to 24 Years Tested in Family Planning Clinics
•Figure B Data, All Regions - Chlamydia – Percentage of Nucleic Acid Amplification Tests Used Among Women Aged 15-24 Years Tested in Family Planning Clinics
Each of the Regional Profiles, one for each of the ten HHS regions, contains a map of the region, a bar graph showing trends in chlamydia positivity rates among women 15 to 24 years of age attending selected family planning clinics, and a bar graph showing trends in the proportion of all chlamydia tests performed that were nucleic acid amplification tests (NAATs). NAATs are the most sensitive tests currently available for the detection of genital Chlamydia trachomatis infections and may be performed on a variety of biologic specimens.
State Profiles
•Figure A Data, All States - Chlamydia rates among women, 2001 - 2011
•Figure B Data, All States - Chlamydia positivity among women aged 15 - 24 years, by testing site, 2001 - 2011
•Figure C Data, All States - Chlamydia positivity among women tested in family planning clinics, by age group, 2011
•Table 1 Data, All States - Chlamydia positivity among women aged 15 - 24 years of age, by testing site, 2011
Each of the State Profiles on chlamydia positivity trends contains three figures and one table.
Morbidity Surveillance: Reporting of Chlamydia Cases
Crude case rates (reported cases/population) were calculated on an annual basis per 100,000 population. Rates for all states were calculated by dividing the number of cases reported from each state by the estimated state-specific population (the most current detailed population file available at time of publication).
From 2001 to 2002, population estimates for Puerto Rico were obtained from the Bureau of Census, and estimates for the Virgin Islands were obtained from the University of the Virgin Islands. After 2002, population estimates for all outlying areas were obtained from the Bureau of Census website.
Due to use of updated population data, rates presented in the current State Profiles may be different from prior State Profiles.
Positivity in Screened Populations: Reporting of Chlamydia Positivity
Chlamydia test positivity was calculated by dividing the number of women testing positive for chlamydia (numerator) by the total number of women tested for chlamydia (denominator includes those with valid test results only and excludes unsatisfactory and indeterminate tests) and is expressed as a percentage. The denominator may contain multiple tests from the same individual if that person was tested more than once during the period for which screening data are reported. The numerator may also contain multiple positive test results from the same individual if that person tested positive more than once during the period for which screening data are reported. Various chlamydia laboratory methods were used and no adjustments of test positivity were made based on laboratory test type and sensitivity.
The number of clinics cited in Table 1 for each state represents family planning (FP), sexually transmitted disease (STD), prenatal, and other clinics screening 25 or more women and juvenile and adult corrections facilities screening 100 or more women. To be included in Figure B, FP and STD clinics must have each had data on at least 50 tests in any given year and the National Job Training Program must have had data on 100 or more entrants in any given year. Each age group displayed in Figure C represents data on at least 100 tests within the past year.
City Profiles
City Profiles have been discontinued. Local areas are encouraged to create their own profiles to best reflect their geographic area and available data. Data on chlamydia cases and rates for selected metropolitan statistical areas are in the current STD surveillance report.
Data Sources
Health and Human Services Regions
Chlamydia screening and monitoring activities were initiated in Health and Human Services (HHS) Region X in 1988 as a CDC-supported demonstration project. In 1993, chlamydia screening services for women were initiated in three additional HHS regions (III, VII, VIII); in 1995, services were implemented in the remaining HHS regions (I, II, IV, V, VI, IX). All DHHS regions, in collaboration with state STD and family planning programs, reported chlamydia positivity data to CDC through 2011. Venues collecting positivity data included family planning clinics, STD clinics, prenatal clinics, jails and juvenile detention centers, and other sites.
The 10 HHS regions referred to in the text and figures are as follows:
- Region I: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont
- Region II: New Jersey, New York, Puerto Rico, and U.S. Virgin Islands
- Region III: Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, West Virginia
- Region IV: Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, Tennessee
- Region V: Illinois, Indiana, Michigan, Minnesota, Ohio, Wisconsin
- Region VI: Arkansas, Louisiana, New Mexico, Oklahoma, Texas
- Region VII: Iowa, Kansas, Missouri, Nebraska
- Region VIII: Colorado, Montana, North Dakota, South Dakota, Utah, Wyoming
- Region IX: Arizona, California, Hawaii, Nevada
- Region X: Alaska, Idaho, Oregon, Washington
See http://www.hhs.gov/about/agencies/staff-divisions/iea/regional-offices/index.html for a map.
State and Local Health Departments
As of 2000, all 50 states and the District of Columbia had regulations requiring the reporting of chlamydia cases.
National Job Training Program
The National Job Training Program is primarily a residential job training program for urban and rural economically-disadvantaged youth 16 to 24 years of age at more than 100 sites throughout the country. Since 1990, approximately 20,000 female National Job Training Program entrants have been screened each year for chlamydia, with all tests performed at a central contract laboratory. Changes in the test type used for females occurred in 1998, switching from the EIA to the DNA hybridization probe (GenProbe PACE 2). Beginning in 2000, a small proportion of females were screened using the strand displacement assay (BDProbeTec ET). By 2006, most females were screened using the strand displacement assay. Since July 2003, male National Job Training Program entrants have also been screened for chlamydia using the strand displacement assay. Annually, over 35,000 men are screened. The chlamydia test results from the National Job Training Program were used to calculate prevalence in this population.
Data Limitations
The interpretation of chlamydia data is complicated by several factors. First, as chlamydia is usually asymptomatic, case report data are influenced by screening coverage. Second, both case report and positivity data result from the use of several different types of diagnostic tests for chlamydial infection (e.g., direct fluorescent antibody, EIA, DNA probe assay, nucleic acid amplification); these tests vary in their sensitivity and specificity. Third, chlamydia positivity in women attending clinics is an estimate of prevalence in the screened population; it is not true prevalence. Crude positivity may include those women who are tested two or more times during a single year. Comparisons of positivity with prevalence have shown that in family planning clinics, positivity is generally similar to or slightly higher than prevalence, and in STD clinics, positivity is somewhat lower than prevalence; however, these differences are usually small, with a relative difference of less than 10% (Dicker et al., 1998). However, prevalence among screened populations is likely higher than prevalence in the general population as women may seek care for reasons related to chlamydial infections. Fourth, family planning and other clinic-based data reported to CDC may not be fully representative of the entire clinic population. Reporting completeness requirements and programmatic influences may lead to only partial reporting from some clinics. Additionally, clinics submitting positivity data to CDC may change over time. Consequently, data trends should be interpreted with caution.
In the National Job Training Program, data are limited to entrance exam testing; therefore, no one is included twice and true prevalence is ascertained as all persons entering the National Job Training Program are required to be tested. However, these data cannot be generalized to the population not entering the National Job Training Program.
As noted above, various laboratory test methods were used for all data. The figures presented in this report do not include an adjustment of test positivity based on laboratory test type and sensitivity.
All 2011 Chlamydia National, Regional and State Profiles
All Years Chlamydia Profiles and Prevalence Monitoring Project Annual Reports
- Page last reviewed: March 1, 2013 (archived document)
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