• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Laboratory Method Files
• Laboratory Quality Assurance and Monitoring
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • SEQN - Respondent sequence number
  • LBXHIVC - HIV-1, 2 Combo Test
  • LBXHIV1 - HIV-1
  • LBXHIV2 - HIV-2
  • LBXHNAT - HIV Confirmatory Test

National Health and Nutrition Examination Survey

2017-2018 Data Documentation, Codebook, and Frequencies

HIV Antibody Test (HIV_J)

Data File: HIV_J.xpt

First Published: February 2020

Last Revised: NA

Component Description

The estimated prevalence of human immunodeficiency virus (HIV) infection in the United States population is an important measure of the extent of the medical and financial burden the nation faces due to this virus. The current NHANES (1999-present) and HIV antibody data from NHANES III (1988-94) serves as a baseline for monitoring the changes in the epidemic over time in the general population of the United States.

Eligible Sample

Examined participants aged 18–59 years were eligible.

Description of Laboratory Methodology

HIV serological and molecular blood test results:

Specimens are initially tested using the GS Combo Ag/Ab Enzyme Immunoassay (EIA) (Bio-Rad Laboratories, Redmond, WA) test method. This test detects simultaneously HIV-1 p24 antigen and antibodies to HIV-1, both groups M and O, and HIV-2. Any specimen that is initially reactive in the screening test is retested in duplicate with the same test. Initially reactive specimens that are reactive in either or both of the duplicates in the repeat testing are referred to as “repeatedly reactive.” Repeatedly reactive specimens are tested with the Bio-Rad Geenius HIV-1/2 Supplemental assay, which both detects and differentiates antibodies to HIV-1 and HIV-2. Geenius results that are antibody-negative or indeterminate and cannot be differentiated as HIV-1 or HIV-2 are further tested using the Hologic Aptima HIV-1 RNA Qualitative Assay to confirm HIV-1 infection.

Refer to the Laboratory Method Files section for a detailed description of the laboratory methods used.

There were no changes to the lab site or equipment for this component in the NHANES 2017-2018 cycle, but there were changes to the lab method during this cycle.

Laboratory Method Files

HIV Combo Laboratory Procedure Manual (February 2020)

HIV Multispot Laboratory Procedure Manual (February 2020)

HIV NAT Laboratory Procedure Manual (February 2020)

Laboratory Quality Assurance and Monitoring

Serum specimens were processed, stored, and shipped to the Laboratory Branch, Division of HIV/AIDS Prevention (DHAP) in the National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention (NCHHSTP), Centers for Disease Control and Prevention, Atlanta, GA for analysis.

Detailed instructions for 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 Laboratory Branch 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 quality-control 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.

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% of all specimens.

NCHS developed and distributed a quality control protocol for all CDC and contract laboratories, which outlined the use of Westgard rules (Westgard, et al. 1981) when running NHANES samples. 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.

Data Processing and Editing

The data were reviewed. Incomplete data or improbable values were returned 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. The specimen availability can also vary by age or other population characteristics. For example, in 2017-2018, approximately 80% 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.

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.

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.

The 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).

Detection Limits

Since this data is reported as qualitative data, the use of lower limit of detection (LLOD) isn’t applicable.

References

• Westgard J.O., Barry P.L., Hunt M.R., Groth T. A multi-rule Shewhart chart for quality control in clinical chemistry. Clin Chem (1981) 27:493-501.

Codebook and Frequencies