The fasting questionnaire is administered
to determine the fasting status of the survey participant. Questions include
but are not limited to: length of “food”
fast, whether the participant had gum or mints, coffee or tea, or alcohol or
dietary supplements prior to their laboratory examination.
participants aged 1 year and older were eligible.
Description of Laboratory Methodology
phlebotomist administered the questionnaire to determine the fasting status of
the survey participant.
There were no
changes to the questionnaire or lab site for this component in the NHANES
Laboratory Quality Assurance and Monitoring
instructions on specimen collection and processing are discussed in the NHANES Laboratory Procedures Manual (LPM).The NHANES quality control and quality assurance protocols (QA/QC) meet the
1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions
are discussed in the NHANES LPM.
Data Processing and Editing
questionnaire data were recorded directly into a computerized database; all
forms used in the MEC were automated.
Refer to the 2017-2018 Laboratory Data Overview for general information on NHANES laboratory data.
Demographic and Other Related Variables
The analysis of
NHANES laboratory data must be conducted using the appropriate survey design
and demographic variables. The NHANES 2017-2018 Demographics File contains demographic data, health indicators, and other related
information collected during household interviews as well as the sample weight
recommended procedure for variance estimation requires use of stratum and PSU
variables (SDMVSTRA and SDMVPSU, respectively) in the demographic data file.
This Fasting Questionnaire File
includes auxiliary information such as fasting status, length of fast, and the
time of venipuncture.
This laboratory data file can be linked to the other NHANES
data files using the unique survey participant identifier (i.e., SEQN).
Use PHAFSTHR and
PHAFSTMN to determine the duration of fasting in hours and minutes,
respectively. When calculating a fasting time in hours and minutes, pay careful
attention to the other times in hours and minutes. For example, the survey
participants were asked: "When was the last time you ate or drank anything
other than plain water? Do not include diet soda or black coffee or tea with
artificial sweeteners like Sweet'N Low, NutraSweet, Equal, or Splenda."
Survey participants were then asked questions PHQ020 to PHQ060: "Have you
had any of the following since the last time you ate or drank anything other
than plain water? Coffee or tea with cream or sugar (include milk or non-dairy
creamers); Alcohol, such as beer, wine, or liquor; Gum, breath mints, lozenges,
cough drops, or cold remedies; Antacids, laxatives, or anti-diarrheal; Dietary
supplements such as vitamins and minerals."
If you are using
fasting status in any of your analyses, please consider the answers to
PHACOFHR/PHACOFMN, PHAALCHR/PHAALCMN, PHAGUMHR/PHAGUMMN/ PHAANTHR/PHAANTMN, and
PHASUPHR/PHASUPMN with the times in hours and minutes in addition to the
PHAFSTHR and PHSFSTMN times.
Use PHDSESN to
determine the session in which the participant was examined.
Please refer to
the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further
details on the use of sample weights and other analytic issues.