• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Laboratory Quality Assurance and Monitoring
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • SEQN - Respondent sequence number
  • WTSSTT2Y - SSTOCA and SSTOXO 2 year weights
  • SSTCAMFI - Toxocara mean florescent intensity
  • SSTCAR - Toxocara antibody result

National Health and Nutrition Examination Survey

2011-2012 Data Documentation, Codebook, and Frequencies

Antibody to Toxocara spp. (Surplus) (SSTOCA_G)

Data File: SSTOCA_G.xpt

First Published: January 2017

Last Revised: April 2022

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

• Anderson JP, Rascoe LN, Levert K, Chastain HM, Reed MS, Rivera HN, McAuliffe I, Zhan B, Wiegand RE, Hotez PJ, Wilkins PP, Pohl J, Handali S. Development of a Luminex bead based assay for diagnosis of toxocariasis using recombinant antigens Tc-CTL-1 and Tc-TES-26. PLoS Negl Trop Dis. 2015 Oct 20;9(10):e0004168. doi: 10.1371/journal.pntd.0004168. eCollection 2015.

Codebook and Frequencies