Table of Contents

Component Description

All available sera from residual specimens from NHANES 2013-2014 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+ from 2013-2014 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 deviations 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 response to rTc-CTL-1 was greater than the cut-off point value (23.1 mean fluorescence intensity [MFI]) and negative test if the response was ≤ 23.1 MFI.

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

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
-9 to 20830.5 Range of Values 6600 6600
. Missing 0 6600

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 371 371
2 Negative 6229 6600
. Missing 0 6600