National Health and Nutrition Examination Survey

This section provides data for three consecutive blood pressure (BP) measurements and other methodological measurements to obtain an accurate blood pressure.

Heart rate is measured on all children 0-7 years of age; radial pulse is measured on participants 8 years and older; and blood pressure (BP) is measured on all participants 8 years and older.

After resting quietly in a seated position for 5 minutes and once the participants maximum inflation level (MIL) has been determined, three consecutive blood pressure readings are obtained. If a blood pressure measurement is interrupted or incomplete, a fourth attempt may be made. All BP determinations (systolic and diastolic) are taken in the mobile examination center (MEC). Participants with any of the following on both arms were excluded from the exam: rashes, gauze dressings, casts, edema, paralysis, tubes, open sores or wounds, withered arms, a-v shunts, radical mastectomy, or if BP cuff does not fit on the arm.

The BP examiners are certified for blood pressure measurement through a training program from Shared Care Research and Education Consulting. Certification is achieved when physician examiners meet all requirements of the training program. The initial training includes: 

• didactic instruction about BP measurement and propensity for error; 
• listening to systolic and diastolic BP sounds using a standardized audio-video tape presentation; 
• an audio-video tape test; 
• a written exam; and
• simultaneously listening to BP on a minimum of 20 volunteers, of all ages, through a Y- stethoscope to compare measures with a gold standard instructor who does the same.

Certification requires a score of 100 percent on the audio-video tape test. Correct answers on the audio-video tape test require the examiner’s answers and the standardized test answers to be within +/- 2mm of mercury (Hg) on 92 percent of 24 measures (12 systolic, 12 diastolic), and within +/- 4mmHg on 100 percent of 24 measures (12 systolic, 12 diastolic).

For more details on the QA/QC process for this component, please refer to the Physician Examination Manual located on the NHANES website at the following link: https://wwwn.cdc.gov/nchs/nhanes/continuousnhanes/manuals.aspx?BeginYear=2013

The following are some specifications used in capturing the BP data:

Systolic blood pressure and maximum inflation level cannot be greater than 300 mmHg;

Systolic and diastolic blood pressure measurements and the maximum inflation level can be even numbers only;

Systolic blood pressure must be greater than diastolic blood pressure;

If there is no systolic blood pressure, there can be no diastolic blood pressure. (There can be a systolic measurement without a diastolic measurement.); and

Diastolic blood pressure can be zero.

        Changes Since 2011-2012:

Exam sample weights should be used for analyses. Please refer to the NHANES Analytic Guidelines (https://wwwn.cdc.gov/nchs/nhanes/analyticguidelines.aspx) and the on-line NHANES Tutorial (https://www.cdc.gov/nchs/tutorials/) for further details on the use of sample weights and other analytic issues.