See the general documentation on Second Day laboratory exams. Also, see the documentation for the primary exam data for Laboratory 39 (Erythrocyte Protoporphyrin).
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 nutritionprograms 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.
Participants aged 16-69 years who do not meet any of the exclusion criteria.
Erythrocyte Protoporphyrin (LBXEPP)
Note: Erythrocyte Protoporphyrin was performed at Centers for Disease Control and Prevention in 2001 and the State of New York Department of Health in 2002.
Division of Laboratory Sciences, Centers for Disease Control and Prevention
Free erythrocyte protoporphyrin (FEP) is measured by a modification of the method of Sassa et al. Protoporphyrin is extracted from EDTA whole blood into a 2:1 (v/v) mixture of ethyl acetate acetic acid, then back extracted into diluted hydrochloric acid. The protoporphyrin in the aqueous phase is measured fluorometrically at excitation and emission wavelengths of 404 and 658 nm, respectively. Calculations are based on a processed protoporphyrin IX (free acid) standard curve. After a correction for the individual hematocrit is made, the final concentration of protoporphyrin in a specimen is expressed as micrograms per deciliter (ug/dL) of packed red blood cells (RBC).
State of New York Department of Health, Wadsworth Center, Trace Elements Laboratory
Porphyrins and heme components are extracted from whole blood into a 4:1 mixture of ethyl acetate-acetic acid. Porphyrins are then separated from heme by back-extraction into a 1.5 M hydrochloric acid solution, and quantitatively determined by molecular fluorometry using a spectrofluorometer calibrated with protoporphyrin IX (PPIX) standard solutions; however, the exact concentration of the standards must first be established using molecular absorbance, Beer’s Law, and the millimolar absorptivity of PPIX.
The analytical method for EP routinely employed is based largely on those originally described by Sassa et al. (1973) and Chisolm and Brown (1975). The extraction method owes much to contributions from other public health labs, including the CDC, and closely follows the key elements of the consensus method for EP as published by the National Committee for Clinical Laboratory Standards (NCCLS C42-A, 2001). At the invitation of Dr. Sassa, the EP Laboratory’s routine method for EP was published as Unit 8.8 in Current Protocols in Toxicology, 1999 by J. Wiley & Sons, Inc.
Specimens were processed, stored and shipped to Division of Laboratory Sciences, National Center for Environmental Health, National Centers for Disease Control and Prevention, Atlanta, Georgia in 2001 and to the State of New York Department of Health, Wadsworth Center, Trace Metals Laboratory, Albany, New York in 2002.
Detailed specimen collection and processing instructions was discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Vials are stored under appropriate frozen (-20o) conditions until they are shipped to the laboratory for testing. Read the LABDOC file for detailed data processing and editing protocols.
The NHANES quality control and quality assurance protocols (QA/QC) meet the 1988 Clinical Laboratory Improvement Amendments mandates. A detailed quality control and quality assurance instruction are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Read the LABDOC file for detailed QA/QC protocols.
The second day exam data was a convenience sample and thus did not have sample weights. 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. They also contain all survey design variables required to analyze these data. The Phlebotomy Examination file includes auxiliary information such the conditions precluding venipuncture. The Household Questionnaire and Phlebotomy Examination files may be linked to the laboratory data file using the unique survey participant identifier SEQN.
The Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention performed testing from 1999-2001. The State of New York Department of Health, Wadsworth Center, Trace Elements Laboratory began testing in 2002.
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 3 to 47 | Range of Values | 550 | 550 | |
| . | Missing | 1 | 551 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 17 to 312 | Range of Values | 550 | 550 | |
| . | Missing | 1 | 551 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 0.3 to 5.52 | Range of Values | 550 | 550 | |
| . | Missing | 1 | 551 |