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.
Male and female participants aged 1-5 years, and female participants 12 to 49 years, who do not meet any of the exclusion criteria, are eligible.
Serum specimens are 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 Laboratory/Medical Technologists Procedures Manual (LPM). Vials are stored under appropriate frozen (–30°C) conditions until they are shipped to National Center for Environmental Health for testing.
Roche Elecsys-170:
The method for measurement of Ferritin on the Roche Elecsys-170 is a sandwich principle with a total duration time of 18 minutes. The 1st incubation uses 10 uL of sample, a ferritin-specific antibody and a labeled ferritin-specific antibody to form a sandwich complex. The 2nd incubation occurs after the addition of microparticles that cause the complex to bind to the solid phase. The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier. Results are determined via a calibration curve.
In 2007-2008 Roche /Hitachi 912 clinical analyzer was used. In 2009-2010 the Roche Elecsys 170 clinical analyzer was used.
Read the General Documentation of Laboratory Data file for detailed data processing and editing protocols. The analytical methods are described in the Analytic Notes for Data Users section below.
One calculated variable (LBDFERSI) was created in this data file. The formula for its derivation is as follows:
The ferritin measurement in ng/mL was converted to µg/L by multiplying by 1.0.
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 General Documentation of Laboratory Data file for detailed QA/QC protocols.
Regression equation to compare 2009-2010 and 2007-2008 Ferritin data:
A crossover study was performed to compare the 2009-2010 Ferritin data to the 2007-2008 Ferritin data. The Roche Hitachi 912 nepholometric immunoassay was used in 2007-2008. The Roche Elecsys 170 sandwich immunoassay was used in 2009-2010. A Deming regression analysis was performed and the following regression was obtained for Ferritin (ng/mL):
Log10 (E170) = 0.989*Log10(Hitachi 912) + 0.049 or
E170 = 10**(0.989*Log10(Hitachi 912) + 0.049)
The regression was based on 773 paired values with a r=0.986.
This regression equation should be used to trend the Ferritin data.
The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES 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.
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.
Exam sample weights should be used for analyses. Please refer to the Analytic Guidelines for further details on the use of sample weights and other analytic issues. The Analytic Guidelines are available on the NHANES website.
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 2 to 1090 | Range of Values | 2909 | 2909 | |
| . | Missing | 612 | 3521 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 2 to 1090 | Range of Values | 2909 | 2909 | |
| . | Missing | 612 | 3521 |