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[Total serum IgE levels. Comparative study of the Kallestad and Pharmacia techniques]
A Sabbah1, H Kerdranvat, M G Lauret
1Laboratoire d'Immuno-Allergologie, CHU, Angers, France.
The Kallestad technique for measurement of total IgE is based on a "sandwich" technique that uses a solid phase (wells in a sensitised microplate) as a separator. The samples that contain the IgE and monoclonal anti-IgE antibodies (AcM anti-IgE) are incubated in the wells sensitised with goat anti-mouse IgE. The AcM anti-IgE binds the IgG and the complex is then bound to the wells by the anti-mouse IgG. After washing, anti IgE marked with alkaline phosphatase is added and this binds to the previously linked IgE. The intensity of colouration is directly proportional to the concentration of IgE in the sample and is measured by spectrophotometry. The Kallestad technique has very great sensitivity (> 1 KUI/L) for a serum sample of 20 microliter. The measurement is quick, with 2 h incubation. There was good intra-assay reproducibility for values 2 to 1100 KUI/L with CV of 7.6. This good reproducibility was also found in inter-assays for values between 2 and 10 KUI/L. The Kallestad technique was evaluated firstly against the CAP RIA System of Pharmacia and secondly, for values against the kit RIA Ultra. For a population labelled "all comers" with values between 2 to 1100 KUI/L the statistical analysis showed no significant difference between the two techniques. The statistical analysis of the study of low values, made with the RIA Ultra kit showed that there was a significant difference between the two techniques. Exchange of standards between the two methods showed a certain over-evaluation of the values of Pharmacia whilst measurements with the Kallestad standards showed a relative under-evaluation. It should be noted that the comparison has been made between a RIA (Pharmacia) technique and one of EIA (Kallestad).
The Kallestad technique for measurement of total IgE is based on a "sandwich" technique that uses a solid phase (wells in a sensitised microplate) as a separator. The samples that contain the IgE and monoclonal anti-IgE antibodies (AcM anti-IgE) are incubated in the wells sensitised with goat anti-mouse IgE. The AcM anti-IgE binds the IgG and the complex is then bound to the wells by the anti-mouse IgG. After washing, anti IgE marked with alkaline phosphatase is added and this binds to the previously linked IgE. The intensity of colouration is directly proportional to the concentration of IgE in the sample and is measured by spectrophotometry. The Kallestad technique has very great sensitivity (> 1 KUI/L) for a serum sample of 20 microliter. The measurement is quick, with 2 h incubation. There was good intra-assay reproducibility for values 2 to 1100 KUI/L with CV of 7.6. This good reproducibility was also found in inter-assays for values between 2 and 10 KUI/L. The Kallestad technique was evaluated firstly against the CAP RIA System of Pharmacia and secondly, for values against the kit RIA Ultra. For a population labelled "all comers" with values between 2 to 1100 KUI/L the statistical analysis showed no significant difference between the two techniques. The statistical analysis of the study of low values, made with the RIA Ultra kit showed that there was a significant difference between the two techniques. Exchange of standards between the two methods showed a certain over-evaluation of the values of Pharmacia whilst measurements with the Kallestad standards showed a relative under-evaluation. It should be noted that the comparison has been made between a RIA (Pharmacia) technique and one of EIA (Kallestad).