• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Data Processing and Editing
• Laboratory Quality Assurance and Monitoring
• Analytic Notes
• Codebook
  • SEQN - Respondent sequence number
  • KIQ110 - Willing to have blood tested for PSA
  • KIQ115 - Infection or inflammation of prostate
  • KIQ185 - Rectal exam in the last 7 days
  • KIQ191 - prostate biopsy or surgery in last 4 wks
  • KIQ195 - Cystoscopy in the last 4 weeks
  • KIQ201 - Diagnosed with prostate cancer
  • KIQ221 - Age at diagnosis of prostate cancer
  • KIQ241 - Ever had prostate surgery
  • KIQ282 - Surgery for prostate cancer?
  • KIQ301 - Radiation treatment for prostate cancer
  • KIQ311 - Taken medicines for prostate cancer
  • LBXP1 - Total prostate specific antigen (ng/mL)
  • LBXP2 - Free prostate specific antigen (ng/mL)
  • LBDP3 - Prostate specific antigen ratio (%)
  • LBXPS4 - Complex prostate specific antigen(ng/mL)

National Health and Nutrition Examination Survey

2007-2008 Data Documentation, Codebook, and Frequencies

Prostate Specific Antigen (PSA) (PSA_E)

Data File: PSA_E.xpt

First Published: September 2009

Last Revised: NA

Note: See Analytic Notes section for the regression equation for complexed PSA.

Component Description

Prostate cancer is the most common non-skin malignancy among men with approximately 180,000 new cases diagnosed and 37,000 deaths in 1999. The total and free PSA tests have been recognized as tumor markers for the screening, diagnosis and management of prostate cancer.

Total, free and complex prostate specific antigens (PSA) were measured among men age 40 years and older. PSA exclusion questions (KIQ115, KIQ185, KIQ191, KIQ195, KIQ201, KIQ241, KIQ282, KIQ301, and KIQ311) were asked during the physician’s examination. PSA immunoassays were performed on blood specimens using the Hybritech tests (Beckman Coulter, Fullerton, CA).

Eligible Sample

Male participants aged 40 years and older were tested for PSA. Those who reported having any of the following conditions were not eligible for PSA testing:

Current infection or inflammation of the prostate gland (KIQ115)
Rectal exam in the past week (KIQ185)
Prostate biopsy in the past month (KIQ191)
Cystoscopy in the past month (KIQ195)
History of prostate cancer (KIQ201)

Description of Laboratory Methodology

Blood specimens are processed, stored and shipped to University of Washington, Seattle, Washington. Detailed specimen collection and processing instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM).

Free prostate specific antigen
The Access Hybritech free PSA assay is a two-site immunoenzymatic "sandwich" assay. A sample was added to a reaction vessel with mouse monoclonal anti-free PSA alkaline phosphatase conjugate, and paramagnetic particles coated with a second mouse monoclonal anti-free PSA antibody. The free PSA in the sample bound to the immobilized monoclonal anti-free PSA on the solid phase while, at the same time, the monoclonal anti-PSA conjugate reacted with a different antigenic site on the sample free PSA. Separation in a magnetic field and washing removes material not bound to the solid phase. A chemiluminescent substrate, Lumi-Phostm 530 was added to the reaction vessel and light generated by the reaction was measured with a luminometer. The light production was proportional to the concentration of free PSA in the sample. The amount of analyte in the sample was determined by means of a stored, multi-point calibration curve.

Total prostate specific antigen
Total PSA values were obtained using the Hybritech PSA method on the Beckman Access. A second sample was added to a reaction vessel with mouse monoclonal anti-PSA alkaline phosphatase conjugate and paramagnetic particles coated with a second mouse monoclonal anti-PSA antibody. The PSA in the sample bound to the immobilized monoclonal anti-PSA on the solid phase while, at the same time, the monoclonal anti-PSA conjugate reacted with a different antigenic site on the sample PSA. The light production was proportional to the concentration of PSA in the sample.

Complex prostate specific antigen (cPSA)
The ADVIA Centaur cPSA assay quantitatively measures complexed prostate-specific antigen (cPSA) in human serum. Free PSA present in the sample is prevented from reacting with the total PSA antibodies by incubating the sample at 37°C with a free-PSA-specific monoclonal mouse antibody (Pretreatment Reagent), which blocks the free PSA so that it is nonreactive in the ADVIA Centaur cPSA assay. The cPSA in the sample is then measured in the two-site sandwich immunoassay using direct chemiluminometric technology, which uses constant amounts of two antibodies. The first antibody, in the Lite Reagent, is a polyclonal goat anti-PSA antibody labeled with acridinium ester. The second antibody, in the Solid Phase, is a monoclonal mouse anti-PSA antibody, which is covalently coupled to paramagnetic particles. The immunocomplexes of sample cPSA sandwiched and coupled to paramagnetic particles are magnetically separated from unbound components and washed in the cuvette incubation ring. The addition of hydroxyl groups to complete the flash reaction is accomplished by the addition of Acid and Base. The chemiluminescent reaction occurs in the luminometer. The photomultiplier tube (PMT) measures the chemical light reaction that takes place. A direct relationship exists between the amount of cPSA present in the patient sample and the amount of relative light units (RLUs) detected by the system. The amount of cPSA in the sample is determined by means of a stored, multi-point calibration curve.

This assay was developed to aid in the detection of prostrate cancer in men. Biopsy of the prostate is required for the diagnosis of prostate cancer. Further studies are needed to confirm that measuring cPSA is more sensitive than total PSA levels in cancer detection. The concentration of cPSA in a given specimen, as determined by assays from different manufacturers, can vary due to differences in assay methods and reagent specificity and cannot be used interchangeably.

Prostate specific antigen ratio
This ratio was calculated by dividing the free PSA by the total PSA:
LBDP3 = round ((LBXP2/LBXP1)*100) (whole number)

There were no changes (from the previous 2 years of NHANES) to equipment, lab methods or lab site. However, beginning in 2007-2008 measurements of complex PSA (cPSA) was added.

A detailed description of the laboratory method used can be found at NHANES web page.

Data Processing and Editing

Read the General Documentation of Laboratory Data file for detailed data processing and editing protocols. The analytical methods are described in the Analytic methodology section.

The prostate specific antigen ratio is a derived variable. There are fill values. See the NHANES web page link to determine “below detectable limit fill values” for this data.

The lower detectable limit for total PSA is 0.10, 0.05 for free PSA, and 0.06 for cPSA.

Laboratory Quality Assurance and Monitoring

The NHANES quality control and quality assurance protocols (QA/QC) meet the 1988 Clinical Laboratory Improvement Amendments mandates. Detailed quality control and quality assurance instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Read the General Documentation of Laboratory Data file for detailed QA/QC protocols.

A detailed description of the quality assurance and quality control procedures can be found at NHANES web page.

Analytic Notes

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 Questionnaire Data Files contain socio-economic data, health indicators, and other related information collected during household interviews. The Phlebotomy Examination 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.

Data on health conditions that would make a sample person ineligible for PSA testing are missing for some people with non-missing PSA lab data. This happened mainly because some sample persons did not attend the physician’s examination component of the MEC examination where such data were collected. It is advisable to exclude these observations for PSA analyses.

The detection limits was constant for all analytes in the data set. In cases, where the result was below the limit of detection, the value for that variable is the detection limit divided by the square root of two.

Regression equation to compare 2009-2010 and 2007-2008 Complexed PSA data:
A crossover study was performed to compare the 2009-2010 Complexed PSA data to the 2007-2008 Complexed PSA data. The Siemens Centaur Advia immunoassay was used in 2007-2008 and the Siemens Centaur XP immunoassay was used in 2009-2010. A Deming regression analysis was performed and the following regression was obtained for the Complexed PSA (ng/mL):

Y (2009-2010, Centaur XP) = 1.047*X (2007-2008, Centaur Advia)

The regression was based on 117 paired values with a Pearson r = 0.999.
The researcher may want to use this regression equation to trend Complexed PSA data.

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.

Codebook and Frequencies