The NHANES program suspended field operations in March 2020 due to the coronavirus disease 2019 (COVID-19) pandemic. As a result, data collection for the NHANES 2019-2020 cycle was not completed and the collected data are not nationally representative. Therefore, data collected from 2019 to March 2020 were combined with data from the NHANES 2017-2018 cycle to form a nationally representative sample of NHANES 2017-March 2020 pre-pandemic data. These data are available to the public. Please refer to the Analytic Notes section for more details on the use of the data.
Herpes Simplex Virus (HSV) is categorized by two types: HSV-1 and HSV-2. HSV-1 is a common chronic infection that is the cause of most oral herpes or cold sores. HSV-2 is a sexually transmitted infection and can be used as a marker for sexual transmission of other infectious agents. HSV-2 infections are rarely life threatening, but morbidity due to painful genital ulcerations is significant (CDC, 2017).
HSV-2 infection is one of the best markers of sexual risk factors leading to sexually transmitted infections, because: (a) HSV-2 infections are common and, thus, HSV-2 rates are a measure of sexual risk in the broader population beyond high risk groups; (b) HSV-2 infection is almost always a result of sexual transmission and, thus, a specific measure of sexually transmitted infection; (c) HSV-2 infections are not curable and, thus, HSV-2 risk is not influenced by health care-seeking factors; and (d) sensitive, specific, and relatively inexpensive tests for HSV-2 antibody are available. HSV-2 is a very important marker for monitoring the impact of large national efforts, motivated by the HIV epidemic, to reduce risky sexual behaviors.
NHANES laboratory data can be linked to NHANES sexual behavior questions to assist in the understanding of national trends in HIV and sexually transmitted diseases. The availability of sexually transmitted infection and risk factors data in a national sample over time is a unique and invaluable resource for evaluation of national HIV/STD risk-reduction efforts and for risk-based modeling of the burden and trends of sexually transmitted infections.
Examined participants aged 14–49 years, in the NHANES 2017-March 2020 pre-pandemic sample, were eligible. Data from participants aged 14-49 years for HSV-1 and 18-49 years for HSV-2 are included in this dataset. HSV-2 data from participants aged 14–17 years are available in a separate dataset: Herpes Simplex Virus Type-1 and Type -2 – Youth (P_HSV_R). Both datasets may be accessed through the NCHS Research Data Center.
Although extensive antigenic cross-reactivity exists between the two viral types of herpes, a viral glycoprotein specific for HSV-2 (designated gG-2) and a glycoprotein specific for HSV-1 (designated gG-1) have been identified. Monoclonal antibodies and affinity chromatography have been used to purify these glycoproteins and thus provide antigens for type-specific herpes serologic assays. Solid-phase enzymatic immunodot assays are used to detect antibodies reactive to these antigens. The purified glycoprotein, gG-1 or gG-2, is adsorbed to the center of a nitrocellulose disk. The rest of the disk surface is coated with bovine serum albumin to prevent further nonspecific protein adsorption. Incubation of test serum with the disk allows specific antibodies, if present, to bind to the immobilized antigen. After extensive washing to remove non-reactive antibodies, the bound antibodies are detected by sequential treatment with peroxidase-conjugated goat-anti-human IgG and the enzyme substrate (H2O2 with chromogen 4-chloro-1-naphthol). A positive reaction is demonstrated by the appearance of a blue dot at the center of the disk. Serum reactive to an immunodot charged with gG-1 indicates the person being tested has HSV-1 infection. Serum reactive to an immunodot charged with gG-2 indicates the person being tested has HSV-2 infection.
Refer to the Laboratory Method Files section for a detailed description of the laboratory methods used.
Herpes Simplex Virus Laboratory Procedure Manual (August 2021)
Serum specimens were processed, stored, and shipped to Emory University, Atlanta, GA for analysis.
Detailed instructions on specimen collection and processing are discussed in the 2017-2018 and 2019-2020 NHANES Laboratory Procedures Manuals (LPMs). Vials are stored under appropriate frozen (–30°C) conditions until they are shipped to Emory University 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 LPMs.
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 member 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 testing 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.
The COVID-19 pandemic required suspension of NHANES 2019-2020 field operations in March 2020 after data were collected in 18 of the 30 survey locations in the 2019-2020 sample. Data collection was cancelled for the remaining 12 locations. Because the collected data from 18 locations were not nationally representative, these data were combined with data from the previous cycle (2017-2018) to create a 2017-March 2020 pre-pandemic data file. A special weighting process was applied to the 2017-March 2020 pre-pandemic data file. The resulting sample weights in the present file should be used to calculate estimates from the combined cycles. These sample weights are not appropriate for independent analyses of the 2019-2020 data and will not yield nationally representative results for either the 2017-2018 data alone or the 2019-March 2020 data alone. Please refer to the NHANES website for additional information for the NHANES 2017-March 2020 pre-pandemic data, and for the previous 2017-2018 public use data file with specific weights for that 2-year cycle.
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. The specimen availability can also vary by age or other population characteristics. For example, in 2017-March 2020, approximately 76% of children aged 1-17 years who were examined in the MEC provided a blood specimen through phlebotomy, while 95% of examined adults age 18 and older provided a blood specimen. 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.
Demographic and Other Related Variables
The analysis of NHANES laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES2017-March 2020 Pre-pandemic 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.
The 2017-March 2020 Pre-pandemic Fasting Questionnaire File includes auxiliary information, such as fasting status, length of fast and the time of venipuncture.
This laboratory data file can be linked to the other NHANES data files using the unique survey participant identifier (i.e., SEQN).
The items LBXHE1 and LBXHE2 represent type-specific enzymatic immunodot assay results. The type-specific immunodot assays used to detect antibodies reactive to HSV-1 and HSV-2 antigens in NHANES 2019–2020 are the same assays as those used in NHANES 1999–2016 and NHANES III. Therefore, HSV-1 and HSV-2 results from these surveys are identical and comparable for trend analyses.
Since this data is reported as qualitative data the use of lower limits of detection (LLODs) isn’t applicable.
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