This document compares three commercially available enzyme-linked immunosorbent assays (ELISAs) for detecting immunoglobulin G antibodies to tetanus toxoid. Two international reference standards were tested in quadruplicate using each ELISA kit. The Binding Site ELISA provided results most closely matching the reference standards, while the Scimedx ELISA consistently reported lower results and the Euroimmun ELISA higher results. When testing 83 serum samples, the ELISAs showed 78% agreement using manufacturers' cutoffs. The Binding Site ELISA identified the fewest samples (3) as non-protective, compared to 19 for the Scimedx ELISA and 6 for the Euroimmun ELISA. Accurate tetanus antibody testing is important for

1. Review of
Comparison of Three Enzyme-Linked
Immunosorbent Assays for Detection
of Immunoglobulin G Antibodies to Tetanus
Toxoid with Reference
Standards and the Impact on Clinical Practice

2. Author(s)
• Karen H. van Hoeven,
• Connie Dale,
• Phil Foster
• and Barbara Body

3. Introduction
 Accurate determination of the concentrations of
immunoglobulin G (IgG) antibody to tetanus toxoid to
evaluate the immunogenicity of tetanus toxoid
vaccines, determine immune competence in individual
patients, and measure the prevalence of immunity in
populations.
 The performance of three commercially available enzyme-
linked immunosorbent assays (ELISAs) for IgG antibodies to
tetanus toxoid were evaluated.
 Scimedx
 The Binding Site
 Euroimmun

4.  The gold standard assay for the determination of specific
IgG antibodies to tetanus toxoid is the in vivo toxin neutralization
test.
But have many Disadvantage:
 time-consuming,
 relatively expensive,
 subjective, and raises ethical issues regarding the use of live
Mammals.
The End point of INVIVO TOXIN Neutralization assay in mice
is death or paralysis
 The use of accurate and automated in vitro assays
 is desirable for ethical, clinical, and economic reasons.
 highly reproducible, sensitive.
 specific in vitro testing improves the efficiency of the clinical
laboratory.

5. • Serially diluted NIBSC 76/589 and TE-3 human tetanus IgG
immunoglobulin international reference standards were
analyzed in quadruplicate using ELISAs manufactured by The
three assays.
Standard and
sample(s)
Transfer
Vol Starting
concn
(IU/ml)
Amt (l)
of sterile
distilled
water
Working concn
(IU/ml)
TE-3
1
2 to 8
480 7.00
360
0
120
7.00
5.25, 3.94, 2.95,
2.21, 1.66,
1.25, and 0.93,
respectively
NIBSC 76/589
9
10 to 16
300 1.00
180
0
120
1.00
0.60, 0.36, 0.33,
0.13, 0.08,
0.05, and 0.03,
respectively
The National Institute for Biological Standards and Control (NIBSC)

6.  IgG antibodies to tetanus toxoid were measured in 83
deidentified serum specimens using each manufacturer’s ELISA.
 Each ELISA provided linear results when evaluated with the
reference preparations.
 The Binding Site ELISA provided results that closely
corresponded to the reference preparations (y 1.09x 0.08),
whereas the Scimedx ELISA gave results that were consistently
lower (y 0.21x 0.07)
and the Euroimmun ELISA gave results that were consistently
higher (y 1.5x 0.30) than the reference preparation
concentrations.

8.  Using the recommended cutoff for each ELISA
(<0.10 IU/ml), the overall agreement of all of the
ELISA methods was 78%.
 serum samples demonstrated inadequate immunity
with all three assays.

9. MATERIALS AND METHODS
Reference materials:
 NIBSC reagent 76/589 was supplied by NIBSC
in a lyophilized vial containing 9.2 IU.
 It was reconstituted in 9.2 ml of sterile distilled
water to yield a working concentration of 1IU/ml.
Serial dilutions of NIBSC 76/589 were performed
to yield final concentrations.
An ampoule of the first International Standard for
human tetanus immunoglobulin, coded TE-3, was
also obtained from the NIBSC.
TE-3 was supplied lyophilized at 120
IU, reconstituted in 1 ml of sterile distilled water
to yield a working concentration of 120 IU/ml.

10. It was then further diluted to 10 IU/ml by
adding 50 l of the initially reconstituted
solution to 550 l of sterile distilled water.
TE-3 was then rediluted to a starting
concentration of 7 IU/ml by adding
350 l of the previously diluted fluid to 150 l of
sterile distilled water.
 Serial dilutions of TE-3 were performed to
yield final concentrations .
One set of dilutions was made and tested with
all three ELISAs.

11. • Serially diluted NIBSC 76/589 and TE-3 human tetanus IgG
immunoglobulin international reference standards were
analyzed in quadruplicate using ELISAs manufactured by The
three assays.
Standard and
sample(s)
Transfer
Vol Starting
concn
(IU/ml)
Amt (l)
of sterile
distilled
water
Working concn
(IU/ml)
TE-3
1
2 to 8
480 7.00
360
0
120
7.00
5.25, 3.94, 2.95,
2.21, 1.66,
1.25, and 0.93,
respectively
NIBSC 76/589
9
10 to 16
300 1.00
180
0
120
1.00
0.60, 0.36, 0.33,
0.13, 0.08,
0.05, and 0.03,
respectively

12. Serum samples
The ELISAs were compared using 83 serum
samples collected in 2007 and submitted for
diagnostic testing.
These samples would have been discarded but
instead were stored at 20°C prior to testing.

13. Antibody assays
Each of the ELISAs detects IgG antibodies to
tetanus toxoid by an indirect technique.
 Testing was performed on thawed serum
samples and reconstituted reference
materials in strict accordance with the
manufacturers’ specifications using
reagents that were supplied with the kits.

14.  Serially diluted NIBSC standards were run in
quadruplicate at each dilution.
 Serum samples were assayed once in
accordance with general laboratory
procedures.
 Each run included high and low control
solutions provided by the manufacturers.

15. Analysis of data
• Intra-assay imprecision was calculated as means
with a coefficient of variation for the
quadruplicate runs.
The recovery percentage was
calculated by dividing the final result with the
expected result and multiplying by 100.
Linear regression analysis was performed by
using the mean of the quadruplicate
results of each reference standard dilution for
each ELISA.

18. Results
 Results of controls provided by all manufacturers’
ELISAswere within acceptable limits.
 Intra-assay imprecision ranged from 1.22 to 16.68%
 for the Scimedx ELISA, from
0.00 to 9.11%
 for The Binding Site ELISA, and
from 2.96 to24.62% for the Euroimmun ELISA.
 Reproducibility of ELISA tests with dilutions of
reference standards at levels near the protective
antibody titer of 0.1 IU/ml

20. The Binding Site ELISA yielded nonprotective
antibody concentrations in only these 3
samples, whereas 19 samples (22.9%)
according to the Scimedx ELISA and 6
samples (7.2%) according to the Euroimmun
ELISA demonstrated nonprotective
Concentrations .

21. Results of 21 samples showing nonprotective antibody
levels
Scimedx
(cutoff 0.10
IU/ml)
The Binding Site Euroimmun
<0.10
<0.10
<0.10
<0.10
<0.10
<0.10
0.15
0.1
<0.10
<0.10
<0.10
<0.10
<0.10
<0.10
<0.10
<0.10
<0.10
<0.10
<0.10
<0.10
<0.10
0.07
2.09
0.15
0.89
0.28
0.19
0.14
0.19
0.10
0.11
0.08
0.06
0.31
0.32
1.06
0.25
0.54
0.44
0.62
2.06
2.23
0.05
3.64
0.13
1.29
0.25
0.26
0.08
0.06
0.07
0.12
0.07
0.05
0.80
1.17
4.18
0.84
2.19
1.88
3.63
>10.0
>10.0
6 samples
Non
protected Ab
level
7.2%
3 samples
only Non
protected Ab
level
3.6%
19 samples
Non
protected Ab
level
22.9%

22. testing for tetanus antitoxin levels is frequently
used for academic purposes or to test the
immunogenicity of vaccines that are in
commercial development, specific
recommendations have been issued for their
appropriate uses in
clinical practice.
In the 2006 Recommendations of the Advisory
Committee on Immunization Practices, there are
several guidelines that describe when testing for
serum tetanus levels would be warranted.

23. The present study provides valuable
comparative data for laboratories that are
evaluating different manufacturers’ products
for routine use in their own centers.
Each product that was evaluated here
performed well relative to internal precision,
linearity, and internal controls.

24. THANK YOU