• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Laboratory Quality Assurance and Monitoring
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • SEQN - Respondent sequence number
  • WTSSCTJ2 - Surplus specimen SSCH_J_R 2 year weights
  • SSMGIGGQ - Anti-M. genitalium IgG detection level
  • SSMGIGG - Anti-M. genitalium IgG interpretation

National Health and Nutrition Examination Survey

2017-2018 Data Documentation, Codebook, and Frequencies

Mycoplasma genitalium Serology - Serum (Surplus) (SSMG_J_R)

RDC Only Data File: SSMG_J_R.xpt

First Published: August 2025

Last Revised: NA

At this time, this dataset is not available publicly. Access may be obtained through the NCHS Research Data Center (https://www.cdc.gov/rdc).

Component Description

Mycoplasma genitalium serologic assays can be used to identify whether someone has been infected with M. genitalium. Historically, several M. genitalium serologic assays have been used (Baseman, et. al., 2011; Idahl, et. al., 2015; Iverson-Cabral, et. al., 2011; Jurstrand, et. al., 2007; Wang, et. al., 2024). Most use whole cell or lipid-associated membrane protein (LAMP) antigens to estimate prior infection with M. genitalium. One additional assay used recombinant MgPa antigen (Svenstrup, et. al., 2006). Most of these antigen preparations suffer from cross-reactivity with M. pneumoniae. MG075F1 is a recombinant protein fragment of the M. genitalium MG_075 gene, which can distinguish M. genitalium antibodies from M. pneumoniae antibodies and thus has a high specificity (Kildemoes, et. al., 2025). MG075F1 was applied as the target antigen in a Western line immunoblot assay that can be used to estimate M. genitalium seroprevalence (Kildemoes, et. al., 2025).

For participants with available serum specimens, an MG075F1 Western line immunoblot assay was performed to measure serum antibodies to M. genitalium. Specimens with a positive test for IgG, according to reactivity with the MG075F1 band, indicate an antibody response to a previous infection with or exposure to M. genitalium.

Eligible Sample

All examined partcipants aged 14-59 years were eligible.

Description of Laboratory Methodology

The Jensen Laboratory at the Statens Serum Institut in Copenhagen, Denmark performed the Western blots on serum specimens received from the National Center for Health Statistics.

Prior to this study, testing the antibody responses using the MG075F1 Western line blot assay in sera from 101 adults with PCR-confirmed M. genitalium infection demonstrated a sensitivity of 87.1%. A specificity of 95.2% was demonstrated through evaluation of sera from 166 children under 15 years of age with and without M. pneumoniae infection, who were unlikely to have been exposed to sexually transmitted M. genitalium.

MG075F1 Western line blots were performed according to standardized protocols. After staining, the reactivity of the test samples was scored relative to the positive control from 0 (no reactivity) to 4 (strongly positive) by two skilled technicians independently and in a blinded fashion. Scores of 0 and 1 were considered seronegative; scores of 2-4 were considered seropositive.

Laboratory Quality Assurance and Monitoring

Serum specimens were received and accessioned by the Jensen Laboratory at the Statens Serum Institut. After being accessioned, the specimens were stored in a secure −80°C freezer until assaying.

Each Western line blot assay used a pre-determined amount of the MG075F1 antigen prepared from one large batch and aliquoted into vials for single use after thawing. Positive serum controls were similarly prepared from a pool of positive sera and aliquoted into vials for single use after thawing. On each line blot, three of 20 lanes were loaded with the positive control (on both sides and in the middle of the blot). Scoring was performed by two skilled technicians independently and in a blinded fashion. Discrepancies were resolved by blinded scoring by a third technician. Discrepancies were never more than one step. Final scores were entered in the data registration file and all results proofread by an independent person.

Laboratory protocols carefully noted lot-numbers of all reagents. Sera producing a high background were retested once, but in all cases the high background was reproduced. Four results were not scorable due to background.

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 2017–2018 Laboratory Data Overview for general information on NHANES laboratory data.

There are over 800 laboratory tests performed on NHANES participants. However, not all participants provided biospecimens or enough volume for all the tests to be performed. Additionally, availability of specimens for surplus projects is lower than for other laboratory tests performed on NHANES participants. The specimen availability can also vary by age or other population characteristics. Analysts should evaluate the extent of missing data in the dataset related to the outcome of interest as well as any predictor variables used in the analyses to determine whether additional re-weighting for item non-response is necessary.

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.

Subsample Weights

The analytes included in this dataset were measured in examined participants aged 14–59 years and older. Special sample weights are required to analyze these data properly. Specific sample weights for this subsample, WTSSCTJ2, are included in this data file and should be used when analyzing these data. The sample weights created for this file used the examination sample weight, i.e., WTMEC2YR, as the base weight. The base weight was adjusted for additional nonresponse to these lab tests and re-poststratified to the population total using sex, age, and race/Hispanic origin. Participants who were part of the eligible population but who did not provide a serum specimen, or did not have sufficient volume of biospecimens, or who did not give consent for their specimens to be used for future research are included in the file, but they have a sample weight assigned “0” in their records.

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 design 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 the other NHANES data files using the unique survey participant identifier (i.e., SEQN).

References

• Baseman J.B., Cagle M., Korte J.E., et al. Diagnostic assessment of Mycoplasma genitalium in culture-positive women. J Clin Microbiol. (2004) 42(1):203-11.
• Idahl A., Jurstrand M., Olofsson J.I., Fredlund H. Mycoplasma genitalium serum antibodies in infertile couples and fertile women. Sex Transm Infect. (2015) 91(8):589-591.
• Iverson-Cabral S.L., Manhart L.E., Totten P.A. Detection of Mycoplasma genitalium-reactive cervicovaginal antibodies among infected women. Clin Vaccine Immunol. (2011) 18(10):1783-6.
• Jurstrand M., Jensen J.S., Magnuson A., Kamwendo F., Fredlund H. A serological study of the role of Mycoplasma genitalium in pelvic inflammatory disease and ectopic pregnancy. Sex Transm Infect. (2007) 83(4):319-23.
• Kildemoes A.O., Rai O.S.S., Westermann E.P.L., et al. Detection of human IgG antibodies against Mycoplasma genitalium using a recombinant MG075 antigen. J Clin Microbiol. (2025) e0187624.
• Svenstrup H.F., Fedder J., Kristoffersen S.E., Trolle B., Birkelund S., Christiansen G. Mycoplasma genitalium, Chlamydia trachomatis, and tubal factor infertility--a prospective study. Fertil Steril. (2008) 90(3):513-20.
• Wang F., Zhang C., Xiu L., et al. Etiological, sociodemographic and clinical characteristics of sexually transmitted infections and M. genitalium resistance in Shenzhen: a multicenter cross-sectional study in China. Front Cell Infect Microbiol. (2024) 14:1407124.

Codebook and Frequencies