Table of Contents

Locator Record

Title: Two-hour Oral Glucose Tolerance Test (OGTT_E )
Contact Number: 1-866-441-NCHS
Years of Content: 2007 - 2008
First Published: January, 2010
Revised: NA
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Two-hour Oral Glucose Tolerance Test, Diabetes, Glucose, Insulin
Record Source: NHANES 2007 - 2008
Survey Methodology: NHANES 2007 - 2008 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, GHB_E.

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

Blood specimens were processed, stored and shipped to Fairview Medical Center Laboratory at the University of Minnesota, Minneapolis Minnesota for analysis. Detailed specimen collection and processing instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM).

Glucose

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.

A detailed description of the laboratory methods for OGTT can be found in the Laboratory Procedures Manual.

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 calculation 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).

Detailed instructions on specimen collection and processing can be found on the NHANES website.

Laboratory Quality Assurance and Monitoring

The NHANES quality control and quality assurance protocols (QA/QC) meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed quality control and quality assurance instructions are discussed in the NHANES LPM. Read the General Documentation on Laboratory Data file for detailed QA/QC protocols.

A detailed description of the quality assurance and quality control procedures can be found on the NHANES website.

Analytic Notes

Glucose regression equations to compare 2007-2008 and 2005-2006 data:

A crossover study was performed to compare the 2007-2008 glucose data to the 2005-2006 glucose data. The Roche/Hitachi 911 was used in 2005-2006 and the Roche ModP was used in 2007-2008. A Deming regression analysis was done and the following regressions were obtained for glucose (mg/dL):

Y (Roche 911) = X (Roche ModP) – 1.139, n=143, r=0.997, slope was not significant.

Y (Roche ModP) = X (Roche 911) + 1.148, n=143, r=0.997, slope was not significant.

These regression equations should be used to trend the glucose data.

NHANES 2007-2008 Survey Design:

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 for these age groups. The phlebotomy file includes auxiliary information such as the conditions precluding venipuncture. The household questionnaire and phlebotomy 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 2007–2008 two-hour OGTT glucose levels.

There will be two weight files 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_E).

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 486575.123 Range of Values 2779 2779
. Missing 536 3315

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 2283 2283
. Missing 1032 3315

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
2 to 103 Range of Values 2283 2283
. Missing 1032 3315

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
103 to 162 Range of Values 2249 2249
. Missing 1066 3315

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
40 to 140 Range of Values 2249 2249
. Missing 1066 3315

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 to 3 Range of Values 2398 2398
. Missing 917 3315

PHAFSTHR - Total length of 'food fast', hours

Variable Name:
PHAFSTHR
SAS Label:
Total length of 'food fast', hours
English Text:
The time (in hours) between when the examinee last ate or drank anything other than water and the time of the venipuncture.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 40 Range of Values 3223 3223
. Missing 92 3315

PHAFSTMN - Total length of 'food fast', minutes

Variable Name:
PHAFSTMN
SAS Label:
Total length of 'food fast', minutes
English Text:
The time (in minutes) between when the examinee last ate or drank anything other than water and the time of the venipuncture.
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 3223 3223
. Missing 92 3315

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 2233 2233
20 Hemophiliac 4 2237
21 Cancer chemotheraphy within 4 weeks 11 2248
22 Diabetic on medications 357 2605
23 Refused venipuncture 54 2659
24 Ill/faint during test 8 2667
25 Venipuncture unsuccessful 30 2697
26 Currently pregnant 28 2725
27 Refused glucose challenge 89 2814
28 Fasting less than 9 hours 296 3110
29 Came late/left early 37 3147
30 All remaining reasons 168 3315
. Missing 0 3315

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
23 to 468 Range of Values 2233 2233
. Missing 1082 3315

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
1.277 to 25.979 Range of Values 2233 2233
. Missing 1082 3315