Table of Contents

Locator Record

Title: Two-hour Oral Glucose Tolerance Test (OGTT_F )
Contact Number: 1-866-441-NCHS
Years of Content: 2009 - 2010
First Published: January, 2012
Revised: NA
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Two-hour Oral Glucose Tolerance Test, Diabetes, Glucose, Insulin, and OGTT
Record Source: NHANES 2009 - 2010
Survey Methodology: NHANES 2009 - 2010 is a stratified multistage probability sample of the civilian non-institutionalized population of the U.S.
Medium: NHANES Web site; SAS transport files

Component Description

Diabetes mellitus was assessed by measures of fasting plasma glucose, two-hour glucose (OGTT) and serum insulin in participants, aged 12 years and over, who were examined in the morning (AM) session only. Glycohemoglobin measures were collected in a full sample and are available in a separate dataset, GLU_F.

Diabetes is a leading cause of disease and death in the United States. Eight million Americans are known to have diabetes, and an approximately equal number have undiagnosed diabetes. In 1993, nearly 18 percent of all deaths, for persons over the age of 25, were among people with diabetes. The prevalence of diabetes and overweight (one of the major risk factors for diabetes) continues to increase. Substantial new efforts to prevent or control diabetes have begun, including the Diabetes Prevention Trial and the National Diabetes Education Program.

Diabetes testing provides population data to: 1) determine a national estimate of diabetes disease prevalence (diagnosed and undiagnosed), 2) identify the risk factors of diabetes disease; 3) permit a national cohort to be established for follow-up studies of this condition; and 4) provide critical information to clinicians and public health officials for the development of preventive care and community-based interventions.

Eligible Sample

Participants, aged 12 years and older, who were examined in the morning session, were eligible.  This is a subsample of the NHANES and requires the use of special weights (See Analytic Notes below).

Description of Laboratory Methodology

Plasma specimens were processed, stored and shipped to Fairview Medical Center Laboratory at the University of Minnesota, Minneapolis Minnesota for analysis.

Glucose concentration was determined by a hexokinase method. It is an endpoint enzymatic method with a sample blank correction.

Beginning in 2005, an oral glucose tolerance test (OGTT) was added to the laboratory protocol. A fasting glucose blood test was performed on all participants, 12 years and older, who were examined in the morning session, after a 9 hour fast. After the initial venipuncture, participants were asked to drink a calibrated dose (generally 75 grams of glucose) of TrutolTM and had a second venipuncture 2 hours (plus or minus 15 minutes) after drinking the Trutol.

There are seven exclusion criteria including hemophilia and chemotherapy safety exclusions, fasting less than 9 hours, taking insulin or oral medications for diabetes, refusing phlebotomy, and not drinking the entire Trutol solution within the allotted time.

There were no changes (from the previous 2 years of NHANES) to equipment, lab methods, or lab site.

Detailed instructions on specimen collection and processing can be found in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM).

Data Processing and Editing

Read the General Documentation on Laboratory Data file for detailed data processing and editing protocols.

The analytical methods are described in the Description of the Laboratory Methodology section.

One calculated variable was created in this data file. The formula for its creation is as follows:

LBXGLT and LBDGLTSI:
The fasting glucose value in mg/dL (LBXGLT) was converted to mmol/L (LBDGLTSI) by multiplying by 0.05551 (rounded to 3 decimals).

Laboratory Quality Assurance and Monitoring

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 Laboratory/Medical Technologists Procedures Manual (LPM). Read the General Documentation on Laboratory Data file for detailed QA/QC protocols.

Analytic Notes

NHANES Survey Design:

The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The Demographic file contains: Status Variables providing core information on the survey participant including examination status, Recoded Demographic Variables including age, gender, race etc., and Interview and Examination Sample Weight Variables and Survey Design Variables. The Questionnaire Data Files contain socio-economic data, health indicators, and other related information collected during household interviews. The Phlebotomy Examination file includes auxiliary information on duration of fasting, the time of day of the venipuncture, and the conditions precluding venipuncture. The Demographic, Questionnaire and Phlebotomy Examination files may be linked to the laboratory data file using the unique survey participant identifier SEQN.

These are new variables that should help the user in the analysis of the two-hour glucose tolerance data:

GTDSCMMN is used to define 
        "Glucose challenge Administer Time in minutes".
GTDDR1MN is used to define: 
        "Time from fast glucose & challenge (min)"
GTDBL2MN is used to define: 
        "Time from fasting glucose & OGTT(min)"
GTDDR2MN is used to define: 
        "Time from glucose challenge & OGTT(min)"
GTXDRANK is used to define: 
        "Amount of glucose challenge the SP drank"
GTDCODE is used to define: 
        "Incomplete OGTT Comment Code"

Sampling Weights
The analyst is strongly encouraged to use the OGTT sampling weights in this file to analyze 2009–2010 two-hour OGTT glucose levels.

There will be two weight variables associated with the subsample for the diabetes data. Use the fasting sample weights (WTSFA2YR) when analyzing the fasting glucose and insulin levels only. Use the OGTT sample weights (WTSOG2YR) when analyzing the insulin, fasting AND OGTT glucose levels or when analyzing ONLY OGTT glucose levels. NOTE: the fasting glucose and insulin weights and data are in a separate file (GLU_F).

When the weights were calculated pregnant women were excluded. However, they based the pregnant women’s pregnancy status on the self-report of pregnancy at the MEC and not whether they were later determined to be pregnant based on the lab test at the MEC. So there are 9 SP’s that have a ridexprg variable equal to 1 in the demographic file but they have a complete OGTT exam and have a weight.

There are 17 SPs who have an OGTT exam values but were diagnosed diabetics. Therefore for weighting purposes they were put in the post strata cell with other diagnosed diabetics. This could be problem from an analytic point of view if they are not analyzed with the other diagnosed diabetics.

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.

References

Codebook and Frequencies

SEQN - Respondent sequence number

Variable Name:
SEQN
SAS Label:
Respondent sequence number
English Text:
Respondent sequence number.
Target:
Both males and females 12 YEARS - 150 YEARS

WTSOG2YR - OGTT Subsample 2 Year MEC Weight

Variable Name:
WTSOG2YR
SAS Label:
OGTT Subsample 2 Year MEC Weight
English Text:
OGTT Subsample 2 Year MEC Weight
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 406363.419 Range of Values 3163 3163
. Missing 0 3163

GTDSCMMN - Glucose challenge Administer Time in min

Variable Name:
GTDSCMMN
SAS Label:
Glucose challenge Administer Time in min
English Text:
Glucose challenge Administer Time in minutes
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 10 Range of Values 2638 2638
. Missing 525 3163

GTDDR1MN - Time from fast glucose & challenge(min)

Variable Name:
GTDDR1MN
SAS Label:
Time from fast glucose & challenge(min)
English Text:
Time from fast glucose & challenge(min)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 102 Range of Values 2638 2638
. Missing 525 3163

GTDBL2MN - Time from fasting glucose & OGTT (min)

Variable Name:
GTDBL2MN
SAS Label:
Time from fasting glucose & OGTT (min)
English Text:
Time from fasting glucose & OGTT (min)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
75 to 206 Range of Values 2581 2581
. Missing 582 3163

GTDDR2MN - Time from glucose challenge & OGTT(min)

Variable Name:
GTDDR2MN
SAS Label:
Time from glucose challenge & OGTT(min)
English Text:
Time from glucose challenge & OGTT(min)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
71 to 141 Range of Values 2581 2581
. Missing 582 3163

GTXDRANK - Amount of glucose challenge drank

Variable Name:
GTXDRANK
SAS Label:
Amount of glucose challenge drank
English Text:
Amount of glucose challenge drank
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 All 2617 2617
2 Some 8 2625
3 None 158 2783
. Missing 380 3163

PHAFSTHR - Total length of 'food fast', hours

Variable Name:
PHAFSTHR
SAS Label:
Total length of 'food fast', hours
English Text:
Total length of 'food fast', hours
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
8 to 23 Range of Values 3163 3163
. Missing 0 3163

PHAFSTMN - Total length of 'food fast', minutes

Variable Name:
PHAFSTMN
SAS Label:
Total length of 'food fast', minutes
English Text:
Total length of 'food fast', minutes
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 59 Range of Values 3163 3163
. Missing 0 3163

GTDCODE - Incomplete OGTT Comment Code

Variable Name:
GTDCODE
SAS Label:
Incomplete OGTT Comment Code
English Text:
Incomplete OGTT Comment Code
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 OGTT complete 2574 2574
20 Hemophiliac 0 2574
21 Cancer chemotherapy within 4 weeks 0 2574
22 Diabetic on medications 302 2876
23 Refused venipuncture 1 2877
24 Ill/faint during test 15 2892
25 Venipuncture unsuccessful 14 2906
26 Currently pregnant 4 2910
27 Refused glucose challenge 18 2928
28 Fasting less than 9 hours 9 2937
29 Came late/left early 19 2956
30 All remaining reasons 207 3163
. Missing 0 3163

LBXGLT - Two Hour Glucose(OGTT) (mg/dL)

Variable Name:
LBXGLT
SAS Label:
Two Hour Glucose(OGTT) (mg/dL)
English Text:
Two Hour Glucose(OGTT) (mg/dL)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
30 to 559 Range of Values 2574 2574
. Missing 589 3163

LBDGLTSI - Two Hour Glucose(OGTT) (mmol/L)

Variable Name:
LBDGLTSI
SAS Label:
Two Hour Glucose(OGTT) (mmol/L)
English Text:
Two Hour Glucose(OGTT) (mmol/L)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1.665 to 31.03 Range of Values 2574 2574
. Missing 589 3163