Table of Contents

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 in the general population and to monitor trends in prevalence as prevention programs are established and expanded.

Eligible Sample

Examined participants aged 14-39 years were eligible. Public data file includes data for persons aged 18-39 years. Please see Analytic Notes about the release of data for adolescents aged 14-17 years.

Description of Laboratory Methodology

The BDProbeTec CT Chlamydia trachomatis 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.

Refer to the Laboratory Method Files section for detailed laboratory procedure manual(s) of the methods used.

There were no changes to equipment, lab methods or lab site.

Laboratory Method Files

Laboratory Quality Assurance and Monitoring

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, Atlanta GA for analysis. Detailed instructions on specimen collection and processing are discussed in the Laboratory Procedures Manual (LPM). Vials are stored under appropriate frozen (–30°C) conditions until they are shipped to Division of AIDS, STD, and TB Laboratory Research for testing.

The NHANES quality assurance and quality control (QA/QC) protocols meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions are discussed in the Laboratory Procedures Manual (LPM).

Mobile Examination Centers (MECs)
Laboratory team performance is monitored using several techniques. NCHS and contract consultants use a structured quality assurance evaluation during unscheduled visits to evaluate both the quality of the laboratory work and the quality-control procedures. Each laboratory staff person is observed for equipment operation, specimen collection and preparation; testing procedures and constructive feedback are given to each staff. Formal retraining sessions are conducted annually to ensure that required skill levels were maintained.

Analytical Laboratories
NHANES uses several methods to monitor the quality of the analyses performed by the contract laboratories. In the MEC, these methods include performing blind split samples collected on “dry run” sessions. In addition, contract laboratories randomly perform repeat testing on 2.0% of all specimens.

Progress reports containing any problems encountered during shipping or receipt of specimens, summary statistics for each control pool, QC graphs, instrument calibration, reagents, and any special considerations are submitted to NCHS quarterly. The reports are reviewed for trends or shifts in the data. The laboratories are required to explain any identified areas of concern.
All QC procedures recommended by the manufacturers were followed. Reported results for all assays meet the Division of AIDS, STD, and TB Laboratory Research’s quality control and quality assurance performance criteria for accuracy and precision.

Data Processing and Editing

The data were reviewed. Incomplete data or improbable values were sent to the performing laboratory for confirmation.

Analytic Notes

Refer to the 2013 - 2014 Laboratory Data Overview for general information on NHANES laboratory data.

Demographic and Other Related Variables
The analysis of NHANES 2013 - 2014 laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES 2013-2014 Demographics File contains demographic data, health indicators, and other related information collected during household interviews as well as the sample weight variables. The demographics file may be linked to the laboratory data file using the unique survey participant identifier (i.e., SEQN).

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).

Detection Limits
Since this data is reported as qualitative data the use of lower LLODs isn’t applicable.

Exam 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.

Codebook and Frequencies

SEQN - Respondent sequence number

Variable Name:
SEQN
SAS Label:
Respondent sequence number
English Text:
Respondent sequence number.
Target:
Both males and females 18 YEARS - 39 YEARS

URXUCL - Chlamydia, urine

Variable Name:
URXUCL
SAS Label:
Chlamydia, urine
English Text:
Chlamydia, urine
Target:
Both males and females 18 YEARS - 39 YEARS
Hard Edits:
to
Code or Value Value Description Count Cumulative Skip to Item
1 Positive 59 59
2 Negative 2115 2174
3 Indeterminate 0 2174
. Missing 42 2216