National Health and Nutrition Examination Survey

Collection of Data

The National Health and Nutrition Examination Survey (NHANES) is a program of periodic surveys conducted by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC). Examination surveys conducted since 1960 by NCHS have provided national estimates of the health and nutritional status of the U.S. civilian non-institutionalized population. To add to the extensive amount of information collected for the purpose of describing the health of the population, DNA specimens were collected during the Third National Health and Nutrition Examination Survey (NHANES III) and Continuous (1999+) NHANES surveys.

NHANES III

NHANES III began in the Fall of 1988 and ended in the Fall of 1994. Survey data were collected and can be analyzed from two phases: Phase-1 was conducted from October, 1988 to October, 1991, and Phase-2 was conducted from October, 1991 to October, 1994. Both phases are nationally representative samples. The genetic data available through the NCHS is from 7159 specimens collected during Phase-2 of the Third National Health and Nutrition Examination Survey (NHANES III).

Oversampling and Frequencies

The NHANES III survey oversampled non-Hispanic Blacks and Mexican-Americans which yielded the following population frequencies for the samples used to generate the genetic data:

Race-Ethnicity	Frequency
Non-Hispanic White	2630
Non-Hispanic Black	2108
Mexican-American	2073
Other*	348
Total	7159

*The "Other" category includes all Hispanics, regardless of race, who were not Mexican-American and also includes all non-Hispanics from racial groups other than white or black.

Laboratory Methodology

The laboratory distributes DNA as aliquots of crude cell lysates. DNA concentrations vary and are estimated to range from 7.5–65 ng/µL with an average of approximately four micrograms in 100 ul. Each 96 well plate is bar-coded and labeled with a readable identifier. Quality control samples (approximately 480 samples) are sent at no charge, either inserted with the NHANES samples or in separate plates, as blind replicates and/or blanks.

Continuous NHANES (1999+)

Continuous NHANES (1999+) Beginning in 1999, NHANES became a continuous, annual survey rather than a periodic survey. Blood samples for DNA purification were collected from participant’s age 20 or more years in survey years 1999-2002. Purified DNA samples are available from these survey years in a single set. DNA samples can be obtained and analyzed with survey data from the National Health and Nutrition Examination Survey 1999-2000 or National Health and Nutrition Examination Survey 2001-2002 or National Health and Nutrition Examination Survey 2007 - 2008

Oversampling and Frequencies

The NHANES 1999-2002 survey oversampled non-Hispanic Blacks and Mexican-Americans which yielded the following population frequencies for the samples used to generate the genetic data:

Race-Ethnicity	Frequency
Non-Hispanic White	4003
Non-Hispanic Black	1350
Mexican-American	1877
Other Race - Including Multi Racial	191
Other Hispanic	418
Total	7839

The NHANES 2007-2008 survey oversampled Mexican-Americans and Other-Hispanic Blacks which yielded the following population frequencies for the samples used to generate the genetic data:

Race-Ethnicity	Frequency
Non-Hispanic White	2222
Non-Hispanic Black	867
Mexican-American	817
Other Race - Including Multi Racial	179
Other Hispanic	526
Total	4611

Laboratory Methodology

The laboratory distributes aliquots of purified DNA of normalized concentrations of 50 nanograms per microliter whenever possible. Some samples may fall below this threshold. Forty microliters of each specimen are supplied. The amount of DNA in each aliquot may vary but are on average are approximately two micrograms. Each 96 well plate is be bar-coded and labeled with a readable identifier. Quality control samples (approximately 480 samples) are sent at no charge, either inserted with the NHANES samples or in separate plates, as blind replicates and/or blanks.