Objective:

In this study, performance characteristics of a tetanus toxoid IgG EIA were investigated.

Methods:

Tetanus vaccines utilise a denatured form of tetanus toxin (tetanus toxoid) and the antibody response to these vaccines can be measured by enzyme immunoassay (EIA). In this study, the performance of Binding Site Ltd UK tetanus toxoid IgG EIA is assessed. In addition a correlation was performed against an in-house EIA from Respiratory and Systemic Infections Laboratory, Central Public Health Lab, London.

Results:

The kit is calibrated against the NIBSC reference material 76/589. The assay measuring range is 0.01–7.0 IU/mL. The analytical sensitivity of the assay was measured at 0.0093 IU/mL.

Intra-assay precision was found to be 5.1% or less by assaying a low, medium and high level sample each 16 times. Inter-assay precision was shown to be 8.8% or less on the same samples measured on three separate occasions.

To determine the effect of potentially interfering substances, high and low samples were assayed with and without the addition of a range of standard interference substances, was <5% variation was observed. Linearity was assessed using three positive samples, comparison of the achieved values by linear regression gave values of greater than R² = 0.998 in each case. A correlation was performed against an in-house EIA from Respiratory and Systemic Infections Laboratory, Central Public Health Lab, London using 71 serum samples. Linear regression showed good correlation with R² = 0.7346. Using a result of >0.1 IU/mL as indicative of a protective level of specific antibodies, the overall correlation of the two assays was 93.3%

Conclusions:

From the results achieved in this study, The Binding Site EIA appears to be a suitable assay for measurement of specific IgG antibodies to tetanus toxoid. The results also correlated well with an existing in-house enzyme immunoassay.