Table of Contents

Locator Record

Title: Second Day Exam - Vitamin A and Vitamin E (VIT_2_R )
Contact Number: 1-866-441-NCHS
Years of Content: 2000 - 2000
First Published: August, 2010
Revised: NA
Access Constraints: RDC Only
Use Constraints: RDC Only
Geographic Coverage: National
Subject:Second Day Exam - Vitamin A and Vitamin E
Record Source: NHANES 2000 - 2000
Survey Methodology: NHANES 2000 - 2000 is a stratified multistage probability sample of the civilian non-institutionalized population of the U.S.
Medium: NHANES Web site; SAS transport files

Component Description

Second Day Exams

See the general documentation on Second Day laboratory exams. Also, see the documentation for the primary exam data for Laboratory 6 (Vitamins A, E and Carotenoids).

Vitamin A (retinol, retinyl palmitate, retinyl stearate), and Vitamin E (a-tocopherol and y-tocopherol)

The objectives of this component are: 1) to provide data for monitoring secular trends in measures of nutritional status in the U.S. population; 2) to evaluate the effect of people's habits and behaviors such as physical activity and the use of alcohol, tobacco, and dietary supplements on people's nutritional status; and 3) to evaluate the effect of changes in nutrition and public health policies including welfare reform legislation, food fortification policy, and child nutrition programs on the nutritional status of the U.S. population. These data will be used to estimate deficiencies and toxicities of specific nutrients in the population and subgroups, to provide population reference data, and to estimate the contribution of diet, supplements, and other factors to serum levels of nutrients. Data will be used for research to further define nutrient requirements as well as optimal levels for disease prevention and health promotion. 

Eligible Sample

Participants aged 16-69 years who do not meet any of the exclusion criteria are eligible.

Description of Laboratory Methodology

Serum concentrations of vitamins A (retinol) and E (α and γ-tocopherol), two retinyl esters, and six carotenoids are measured using high performance liquid chromatography with photodiode array detection. A small volume (100 uL) of serum is mixed with an ethanol solution containing two internal standards- retinyl butyrate and nonapreno-β-carotene (C45). The micronutrients are extracted from the aqueous phase into hexane and dried under vacuum. The extract is redissolved in ethanol and acetonitrile and is filtered to remove any insoluble material. An aliquot of the filtrate is injected onto a C18 reversed phase column and isocratically eluted with a mobile phase consisting of equal parts of ethanol and acetonitrile. Absorbance of these substances in solution is linearly proportional to concentration, thus spectrophotometric methods are used for quantitative analysis. Three wavelengths, approximately corresponding to absorption maxima, namely, 300, 325, and 450 nm, are simultaneously monitored and chromatograms are recorded. Quantitation is accomplished by comparing the peak height of the analyte in the unknown with the peak height of a known amount of the same analyte in a calibrator solution. Calculations are corrected based on the peak height of the internal standard in the unknown compared with the peak height of the internal standard in the calibrator solution. Retinol and the retinyl esters are compared with retinyl butyrate at 325 nm, α and γ-tocopherol are compared with retinyl butyrate at 300 nm, and the carotenoids are compared with C45 at 450 nm.

Data Processing and Editing

Serum specimens were processed, stored, and shipped to the Division of Laboratory Sciences, National Center for Environmental Health, and Centers for Disease Control and Prevention for analysis.

Detailed specimen collection and processing instructions are discussed in the NHANES LPM. Vials were stored under appropriate frozen (–20°C) conditions until they were shipped to National Center for Environmental Health for testing.

This file contains no top coding.

Derived variables were created in this data file. The formula for their derivatization is as follows:

The vitamin A (retinol) results in ug/dL were converted into umol/L by multiplying by 0.03491.

The retinyl palmitate results in ug/dL were converted into umol/L by multiplying by 0.03491.

The retinyl stearate results in ug/dL were converted into umol/L by multiplying by 0.03491.

The vitamin E (a-tocopherol) results in ug/dL were converted into umol/L by multiplying by 0.02322.

The y-tocopherol results in ug/dL were converted into umol/L by multiplying by 0.02402.

Laboratory Quality Assurance and Monitoring

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 Laboratory/Medical Technologists Procedures Manual (LPM). Read the LABDOC file for detailed QA/QC protocols.

A detailed description of the quality assurance and quality control procedures can be found on the NHANES website.

Analytic Notes

The second day exam data was a convenience sample and thus did not have sample weights. The analysis of NHANES 2000 laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES 2000 Household Questionnaire Data Files contain demographic data, health indicators, and other related information collected during household interviews. The Household Questionnaire Data Files also contain all survey design variables and sample weights required to analyze these data. The Phlebotomy Examination file includes auxiliary information on duration of fasting, the time of day of the venipuncture, and the conditions precluding venipuncture. The Household Questionnaire and Phlebotomy Exam files may be linked to the laboratory data file using the unique survey participant identifier SEQN.

References

Codebook and Frequencies

SEQN - Respondent sequence number

Variable Name:
SEQN
SAS Label:
Respondent sequence number
English Text:
Respondent sequence number.
Target:
Both males and females 16 YEARS - 69 YEARS

LB2DAY - Days between 1st and 2nd exam

Variable Name:
LB2DAY
SAS Label:
Days between 1st and 2nd exam
English Text:
The number of days between the collection of the first and second exam
Target:
Both males and females 16 YEARS - 69 YEARS
Code or Value Value Description Count Cumulative Skip to Item
6 to 51 Range of Values 300 300
. Missing 2 302

LB2GTC - gamma-tocopherol(ug/dL)

Variable Name:
LB2GTC
SAS Label:
gamma-tocopherol(ug/dL)
English Text:
gamma-tocopherol(ug/dL)
Target:
Both males and females 16 YEARS - 69 YEARS
Hard Edits:
0 to 9999
Code or Value Value Description Count Cumulative Skip to Item
25.5 to 987 Range of Values 275 275
. Missing 27 302

LB2GTCSI - gamma-tocopherol(umol/L)

Variable Name:
LB2GTCSI
SAS Label:
gamma-tocopherol(umol/L)
English Text:
gamma-tocopherol(umol/L)
Target:
Both males and females 16 YEARS - 69 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.61 to 23.69 Range of Values 275 275
. Missing 27 302

LB2RPL - Retinyl palmitate(ug/dL)

Variable Name:
LB2RPL
SAS Label:
Retinyl palmitate(ug/dL)
English Text:
Retinyl palmitate(ug/dL)
Target:
Both males and females 16 YEARS - 69 YEARS
Hard Edits:
0 to 999
Code or Value Value Description Count Cumulative Skip to Item
0.14 to 18.7 Range of Values 269 269
. Missing 33 302

LB2RPLSI - Retinyl palmitate(umol/L)

Variable Name:
LB2RPLSI
SAS Label:
Retinyl palmitate(umol/L)
English Text:
Retinyl palmitate(umol/L)
Target:
Both males and females 16 YEARS - 69 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 0.65 Range of Values 269 269
. Missing 33 302

LB2RST - Retinyl stearate(ug/dL)

Variable Name:
LB2RST
SAS Label:
Retinyl stearate(ug/dL)
English Text:
Retinyl stearate(ug/dL)
Target:
Both males and females 16 YEARS - 69 YEARS
Hard Edits:
0 to 999
Code or Value Value Description Count Cumulative Skip to Item
0.35 to 7.1 Range of Values 255 255
. Missing 47 302

LB2RSTSI - Retinyl stearate(umol/L)

Variable Name:
LB2RSTSI
SAS Label:
Retinyl stearate(umol/L)
English Text:
Retinyl stearate(umol/L)
Target:
Both males and females 16 YEARS - 69 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.01 to 0.25 Range of Values 255 255
. Missing 47 302

LB2VIA - Retinol(ug/dL)

Variable Name:
LB2VIA
SAS Label:
Retinol(ug/dL)
English Text:
Retinol(ug/dL)
Target:
Both males and females 16 YEARS - 69 YEARS
Hard Edits:
0 to 999
Code or Value Value Description Count Cumulative Skip to Item
22.1 to 232.3 Range of Values 300 300
. Missing 2 302

LB2VIASI - Retinol (umol/L)

Variable Name:
LB2VIASI
SAS Label:
Retinol (umol/L)
English Text:
Retinol(umol/L)
Target:
Both males and females 16 YEARS - 69 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.77 to 8.11 Range of Values 300 300
. Missing 2 302

LB2VIE - alpha-tocopherol(ug/dL)

Variable Name:
LB2VIE
SAS Label:
alpha-tocopherol(ug/dL)
English Text:
alpha-tocopherol(ug/dL)
Target:
Both males and females 16 YEARS - 69 YEARS
Hard Edits:
0 to 9999
Code or Value Value Description Count Cumulative Skip to Item
413.7 to 4235.6 Range of Values 300 300
. Missing 2 302

LB2VIESI - alpha-tocopherol(umol/L)

Variable Name:
LB2VIESI
SAS Label:
alpha-tocopherol(umol/L)
English Text:
alpha-tocopherol(umol/L)
Target:
Both males and females 16 YEARS - 69 YEARS
Code or Value Value Description Count Cumulative Skip to Item
9.61 to 98.35 Range of Values 300 300
. Missing 2 302