• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Data Processing and Editing
• Laboratory Quality Assurance and Monitoring
• Analytic Notes
• Codebook
  • SEQN - Respondent sequence number
  • URXUCL - Urinary Chlamydia
  • URXUGC - Urinary Gonorrhea

National Health and Nutrition Examination Survey

2007-2008 Data Documentation, Codebook, and Frequencies

Chlamydia & Gonorrhea - Urine (CHLMDA_E)

Data File: CHLMDA_E.xpt

First Published: September 2009

Last Revised: NA

Component Description

Sexually transmitted infections caused by Chlamydia trachomatis may lead to pelvic inflammatory disease, ectopic pregnancy, infertility, and chronic pelvic pain in women. They are associated with increased risk of HIV transmission. Pregnant women may transmit infection to their newborn, causing serious medical complications.

NHANES offers an opportunity to assess the prevalence of chlamydia and gonococcal infection in the general population and to monitor trends in prevalence as prevention programs are established and expanded.

Eligible Sample

Participants aged 14-39 years were tested. The public data file includes data for persons 18-39 years of age. Please see Analytic Notes about the release of data for adolescents 14-17 years of age.

Description of Laboratory Methodology

Urine specimens were processed, stored and shipped to the Division of AIDS, STD, and TB Laboratory Research, National Center for Infectious Diseases, National Centers for Disease Control and Prevention for analysis. Detailed specimen collection and processing instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM).

The BDProbeTec CT Chlamydia trachomatis and Neisseria gonorrhoeae Amplified DNA Assays are based on the simultaneous amplification and detection of target DNA, using amplification primers and a fluorescent labeled detector probe. The Strand Displacement Amplification (SDA) reagents are dried in two separate disposable microwell strips. The processed sample is added to the Priming Microwell, which contains the amplification primers, fluorescent labeled detector probe, and other reagents necessary for amplification. After incubation, the reaction mixture is transferred to the Amplification Microwell, which contains two enzymes (a DNA polymerase and a restriction endonuclease) necessary for SDA. The Amplification Microwells are sealed to prevent contamination and then incubated in a thermally controlled fluorescent reader which monitors each reaction for the generation of amplified products. The presence or absence of C. trachomatis and N. gonorrhoeae is determined by relating the BDProbeTec ET MOTA (Method Other Than Acceleration) scores for the sample to pre-determined cutoff values. The MOTA score is a metric used to assess the magnitude of signal generated as a result of the reaction.

There were no changes (from the previous 2 years of NHANES) to equipment, lab methods or lab site.

Data Processing and Editing

Read the General Documentation of Laboratory Data file for detailed data processing and editing protocols. The analytical methods are described in the Analytic Notes for Data Users section below.

Laboratory Quality Assurance and Monitoring

The NHANES quality assurance and quality control (QA/QC) protocols meet the 1988 Clinical Laboratory Improvement Amendments mandates. Detailed quality control and quality assurance instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Read the General Documentation of Laboratory Data file for detailed QA/QC protocols. A detailed description of the quality assurance and quality control procedures can be found on the NHANES website.

Analytic Notes

The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES Household Questionnaire Data Files contain demographic data, health indicators, and other related information collected during household interviews. They also contain all survey design variables and sample weights for these age groups. The phlebotomy file includes auxiliary information, such as the conditions precluding venipuncture. The household questionnaire and phlebotomy files may be linked to the laboratory data file using the unique survey participant identifier SEQN.

Exam sample weights should be used for analyses. Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial  for further details on the use of sample weights and other analytic issues.

The public release data file includes urinary chlamydia data for participants aged 18–39. Data for youth aged 14–17 years are available through the NCHS Research Data Center (RDC).

Codebook and Frequencies