Table of Contents

Component Description

All available sera from residual specimens from NHANES 2009-2010 participants were tested for Toxoplasma gondii by an enzyme immunoassay (EIA) that detects IgG antibodies against T. gondii. All results in this data release are reported as IU/ml. Samples with results ≥ 33 IU/mL should be coded as Positive, samples with results < 27 IU/mL should be coded as Negative, and samples with results ≥ 27 IU/mL and <33 IU/mL were considered Equivocal. All results originally considered Equivocal were repeated at least twice for confirmation and should be coded as Negative.

Eligible Sample

All specimens from 2009-2010 leftover from laboratories who tested them and sent the residual serum back to NCHS repository.

Description of Laboratory Methodology

Toxoplasma gondii antibodies were measured with a highly sensitive and specific Toxoplasma IgG enzyme immunoassay kit (Bio-Rad, Redmond, VA). This test utilizes antigen-coated wells. The samples are incubated in the antigen-coated wells, (if present) T. gondii antibodies are immobilized in the wells. Residual sample is eliminated by washing and conjugate (enzyme labeled antibodies to human IgG) is added and incubated. If IgG antibodies to T. gondii are present, the conjugate will be immobilized in the wells. Residual conjugate is eliminated by washing and the substrate is added. In the presence of the enzyme, the substrate is converted to a yellow end product which is read photometrically. Optical density was determined on a vMax microplate reader and computer equipped with SOFTmax software (Molecular Devices Corp., Menlo Park, CA). 

Quality control samples are included on every plate. The results of serologic tests are of value as presumptive evidence of T. gondii infection. The test results are objective and normalized  as index values, or as International Units (IU/mL), which are traceable to the WHO Anti-Toxoplasma Serum, 3rd International Standard Preparation, 1994. Prior to the study the Toxoplasma IgG EIA was evaluated using an established serum panel and comparison with the CDC Toxoplasma immunofluorescence assay and the Sabin-Feldman dye test and found to have a sensitivity and specificity of 100%.

Data Processing and Editing

Data were submitted after all the antibody testing was complete. The data were not edited.

Laboratory Quality Assurance and Monitoring

The Toxoplasma gondii EIA test is considered in control provided the quality control serum is within two standard deviations of its mean.

Analytic Notes

Results were measured as IU/ml. Samples with results ≥ 33 IU/mL should be coded as Positive, samples with results < 27 IU/mL should be coded as Negative, and samples with results ≥ 27 IU/mL and <33 IU/mL were considered Equivocal. All results originally considered Equivocal were repeated at least twice for confirmation and should be coded as Negative.

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

SSTOXO - T.gondii antibodies (IU/ml)

Variable Name:
SSTOXO
SAS Label:
T.gondii antibodies (IU/ml)
English Text:
T.gondii antibodies (IU/ml)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 332 Range of Values 7070 7070
. Missing 9 7079