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 newborns, 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.
Examined participants aged 14-39 years were eligible. This data file includes information from participants aged 14-17 years. Data from participants aged 18-39 years are available in a separate dataset: Chlamydia - Urine - Adult (CHLA_J_R). Both datasets may be accessed through the NCHS Research Data Center.
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 a detailed description of the laboratory methods used.
There were no changes to the lab method, lab equipment, or lab site for this component in the NHANES 2017-2018 cycle.
Chlamydia Laboratory Procedure Manual (May 2020)
Urine specimens were processed, stored, and shipped to the Division of STD Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention, Centers for Disease Control and Prevention, Atlanta GA for analysis.
Detailed instructions on specimen collection and processing are discussed in the NHANES Laboratory Procedures Manual (LPM). Vials are stored under appropriate frozen (–30°C) conditions until they are shipped to the Division of STD Prevention Laboratory 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 NHANES LPM.
Mobile Examination Centers (MECs)
Laboratory team performance is monitored using several techniques. NCHS and
contract consultants use a structured competency assessment evaluation during
visits to evaluate both the quality of the laboratory work and the QC procedures.
Each laboratory staff person is observed for equipment operation, specimen
collection and preparation; testing procedures and constructive feedback are
given to each staff member. Formal retraining sessions are conducted annually
to ensure that required skill levels were maintained.
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% of all specimens.
NCHS developed and distributed a QC protocol for all CDC and contract laboratories, which outlined the use of Westgard rules (Westgard, et al. 1981) when running NHANES 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.
The data were reviewed. Incomplete data or improbable values were sent to the performing laboratory for confirmation.
Demographic and Other Related Variables
The analysis of NHANES laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES 2017-2018 Demographics File contains demographic data, health indicators, and other related information collected during household interviews as well as the sample weight variables. The recommended procedure for variance estimation requires use of stratum and PSU variables (SDMVSTRA and SDMVPSU, respectively) in the demographic data file.
This laboratory data file can be linked to other NHANES data files using the unique survey participant identifier (i.e., SEQN).
Since this data is reported as qualitative data the use of LLODs isn’t applicable.
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