Table of Contents

Locator Record

Title: Tissue transglutaminase assay (IgA-TTG) and the IgA endomyseal antibody assay (IgA EMA) (TGEMA_F )
Contact Number: 1-866-441-NCHS
Years of Content: 2009 - 2010
First Published: September, 2011
Revised: NA
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Celiac, glutens, TTG, EMA
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

Estimate the prevalence of celiac disease in the United States population.. Celiac disease is an intolerance to dietary glutens that has protean manifestations. In population surveys in other countries, it is found in about 0.5 to 1 percent of the population. It may well be as common in the United States, but has not been adequately examined. Advances in diagnostic testing now allow accurate disease prevalence estimates using two step serological testing. To provide reliable population estimates, four to six years of data collection are required.

Eligible Sample

Participants aged 6 years and older were tested.

Description of Laboratory Methodology

Serum specimens were processed, stored and shipped to the Mayo Clinic, Rochester, Minnesota. Detailed instructions on specimen collection and processing can be found in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM).

Tissue transglutaminase assay (IgA-TTG)

An Enzyme-Linked Immunosorbant Assay (ELISA) for the semi-quantitative detection of IgA antibodies to tissue transglutaminase (endomysium) in human serum. Microwells are pre-coated with recombinant human tTG antigen. The calibrators, controls and diluted patient samples are added to the wells and autoantibodies recognizing the tTG antigen bind during first incubation. Unbound proteins are removed during washing and purified peroxidase conjugate is added which binds to the captured human autoantibody; excess is washed. TMB substrate is added which gives a blue reaction product, intensity is proportional to the concentration of autoantibody in the sample. Phosphoric acid is added to stop the reaction which gives the yellow color. Plate is read at 450 nm.

Endomyseal antibody assay (IgA EMA)

Endomysial antibodies of the IgA subclass present in the serum bind to the reticulin component of the endomysium of the smooth muscle in monkey esophagus tissue and can be detected by indirect immunofluorescence. Substrate-bound IgA antibody is identified with a fluorescein-conjugated anti-human IgA (Fab2-specific) conjugate. Positive staining is identified as a reticulated lace-like pattern on perimucosal smooth muscle bands. Sera positive for endomysial antibody are titered to end-point dilutions.

Data Processing and Editing

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

Laboratory Quality Assurance and Monitoring

The NHANES quality assurance and quality control (QA/QC) protocols 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

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 and sample weights 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. 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 6 YEARS - 150 YEARS

LBXTTG - Tissue transglutaminase(IgA-TTG)

Variable Name:
LBXTTG
SAS Label:
Tissue transglutaminase(IgA-TTG)
English Text:
Tissue transglutaminase(IgA-TTG)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Positive 34 34
2 Negative 7749 7783
3 Weakly positive 15 7798
. Missing 793 8591

LBXEMA - Endomyseal antibody (IgA EMA)

Variable Name:
LBXEMA
SAS Label:
Endomyseal antibody (IgA EMA)
English Text:
Endomyseal antibody (IgA EMA)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Positive 28 28
2 Negative 19 47
3 Weakly positive 2 49
. Missing 8542 8591