Human papillomavirus (HPV) infection is the most common sexually transmitted infection in the United States. Cervical infection with certain types of HPV is causally associated with cervical cancer in women. No national surveillance system exists to measure the full burden of HPV infection, and no reliable national population estimate of HPV exists. NHANES offers a unique opportunity to assess the prevalence of HPV infection in the general population.
Reducing the prevalence of HPV infection is a Developmental Healthy People 2010 objective: “Reducing the number of new HPV cases can help minimize the overall number of cases of high risk subtypes associated with cervical cancer in females ...” Two HPV vaccines are licensed, and knowledge of the national prevalence of HPV infection is critical for planning vaccination strategies and monitoring the impact of vaccination in the United States.
All participants aged 4 to 17 years.
Description of Laboratory Methodology
The IgG assay for HPV 6, 11, 16, 18, 31, 45, 52, and 58 was performed on a prewet, 96-well-microtiter filter plate (Millipore, Billerica, MA). A 12-point standard curve with the reference serum starting at a 1:100 dilution and subsequent 3-fold dilutions, 4 controls, and 16 samples tested at the 1:50 and 1:500 dilutions were added to the plate in duplicate. VLP-microspheres for types 6, 11, 16, 18, 31, 33, 45, 52, and 58 were added to each well at 5,000 VLP-microspheres per HPV type. The plates were covered with foil and incubated for 15 to 60 min. The filter plates were washed twice with PBS-1% Triton X-100 and resuspended in 7.5 μg/ml of a phycoerythrin (PE)-tagged mouse monoclonal antibody (clone HP6043; Biotrend, Destin, FL) that binds equally to human IgG1 to -4 (13). The plates were covered with foil and incubated for an additional 15 to 60 min. Following the second incubation period, the plates were washed twice and then analyzed on a BioPlex200 (Bio-Rad, Hercules, CA). A design-of-experiment (DOE) analysis of primary and secondary incubation times of 15 to 60 min showed that there was less than a 7% difference in antibody titers. The correlation of median fluorescent intensity (MFI) units to mMU/ml of VLP-specific IgG was made by serially diluting the reference serum and interpolating the MFI data through a 4-parameter curve-fitting algorithm.
Data Processing and Editing
Blood specimens were processed, stored and shipped to Atlanta, Ga. for analysis. Detailed specimen collection and processing instructions are discussed in the NHANES LPM. Read the LABDOC file for detailed data processing and editing protocols. The analytical methods are described in the Description of the Laboratory Methodology section. The Competitive Luminex Immunoassay was conducted at Pharmaceutical Product Development (PPD) Inc. using the protocol established by Merck for vaccine clinical trials.
The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The Demographic file contains: Status Variables providing core information on the survey participant including examination status, Recoded Demographic Variables including age, gender, race etc., and Interview and Examination Sample Weight Variables and Survey Design Variables. The recommended procedure for variance estimation requires use of stratum and PSU variables (SDMVSTRA and SDMVPSU, respectively), which are included in the demographic data file for each data release. The Questionnaire Data Files contain socio-economic data, health indicators, and other related information collected during household interviews. The Fasting Questionnaire file includes auxiliary information on duration of fasting, the time of day of the venipuncture, and the conditions precluding venipuncture. The Demographic, Questionnaire and Phlebotomy Examination files may be linked to the laboratory data file using the unique survey participant identifier SEQN.
Refer to the 2011-2012 Laboratory Data Overview for general information on NHANES laboratory data.