Table of Contents

Component Description

All available sera from residual specimens from NHANES 2011-2012 participants were tested for Toxocara spp. by a Luminex assay using recombinant rTc-CTL-1 antigen that detects IgG antibodies against Toxocara spp. All results in this data release are reported as positive or negative.

Eligible Sample

All specimens from males and females aged 6-150 years from 2011-2012 leftover specimens from laboratories that tested them and sent the residual serum back to the NCHS repository.

Description of Laboratory Methodology

Toxocara Assay Procedure in Luminex platform:

MagPlex Immunoassay
Fifty μL of working microsphere mixture (50 beads/μL in PBS/0.3% Tween-20/5% non-fat dry skim milk) and 50 μL of diluted sera (1:100 dilution in PBS/0.3% Tween-20/5% non-fat dry skim milk) were added into each well of Costar 96-well black, round-bottom plate (Fisher Scientific, Cat.# 3792). After 30 minutes incubation at room temperature with shaking at speed 6 (~800 rpm), the beads were washed using Biotek Magnetic Washer ELx50 (2 minutes magnetic separation, and then 2 cycles of dispensing 100 µL of PBS/Tween-20 0.3%, soaks for 40 seconds before aspiration). The complex of antibody and coupled beads was detected using 50 μL of biotinylated mouse anti-human IgG (clone H2, affinity purified, Southern Biotech, Birmingham, AL, Cat. Number 9042-08) diluted 1:200 in PBS-1% BSA, 0.05% NaN3. After 30 minutes incubation, the beads were washed as before. As detector, 50 μL/well of diluted Streptavidin, R-phycoerythrin conjugate (Invitrogen, Cat. # S866) (1:250 dilution in PBS-1% BSA, 0.05% NaN3) was added to the well and incubated for another 30 minutes. After washing, the beads were resuspended using 100 μL/well of PBS-1% BSA, 0.05% NaN3. The mean fluorescence intensity from each well was determined by using BioPlex manager software, version 6.02 (BioRad) in Luminex 100 platform. The mean fluorescence intensity – signal intensity of the blank well is used for further analysis.

Laboratory Quality Assurance and Monitoring

Quality control and assay validation information:

For each run, we ran three controls: Toxocara 100, Toxocara 50, and Toxocara 0 (negative). These 3 controls should be within the mean ± 2 standard deviation of the established value. If the controls of the plate have a value outside of the acceptance range, the whole plate was retested. The assay itself has been validated against reference serum sets and it has a sensitivity of 90% and a specificity of 99%.

Data Processing and Editing

N/A

Analytic Notes

The test was positive if the antibody responses to rTc-CTL-1 was greater than the cut-off point value (23.1 mean fluorescence intensity [MFI]) and negative test if the responses was ≤ 23.1 MFI.

Subsample Weights

Sample weights are required to analyze these data properly. Specific sample weights for this subsample are included in this data file and should be used when analyzing these data. When observations were removed from this data file, a new sample weight was created and  added to this data file (WTSSTT2Y). 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

WTSSTT2Y - SSTOCA and SSTOXO 2 year weights

Variable Name:
WTSSTT2Y
SAS Label:
SSTOCA and SSTOXO 2 year weights
English Text:
Surplus specimen SSTOCA and SSTOXO 2 year weights
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
5700.578442 to 247519.73303 Range of Values 6099 6099
0 No lab specimen 0 6099
. Missing 0 6099

SSTCAMFI - Toxocara mean florescent intensity

Variable Name:
SSTCAMFI
SAS Label:
Toxocara mean florescent intensity
English Text:
Toxocara mean florescent intensity
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
-25.5 to 11745.3 Range of Values 6098 6098
. Missing 1 6099

SSTCAR - Toxocara antibody result

Variable Name:
SSTCAR
SAS Label:
Toxocara antibody result
English Text:
Toxocara antibody result
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Positive 438 438
2 Negative 5660 6098
. Missing 1 6099