Abstract
Background: Parallel line bioassay (PLBA) has been acknowledged to be the gold standard for estimation of changes in reactivity, e.g., in RAST and ELISA inhibition tests. Objective: To study correlations between two simple methods for evaluation of changes in skin prick test (δSPT), using the slope of the allergen dose response (drra) in relation to PLBA. Methods: Skin prick test data from two published immunotherapy trials were used. In a D. farinae trial we used duplicate tests with three fixed ten-fold concentrations and in a P. judaica trial three tenfold individually chosen allergen concentrations causing wheals of similar size to that of histamine dihydrochloride 10 mg/mL, tenfold lower and tenfold higher concentration. Evaluation of the δSPT by PLBA, and two simple methods were correlated. In the D. farinae trial δSPT was compared to the change of conjunctival threshold concentration. Results: The δSPT as measured by both the simple methods gave similar results to that of PLBA (p<0.001). The δSPT was around 30-fold, i.e., about 3% of the pre-treatment reactivity. The δSPT correlated with the δCPT threshold concentration. Conclusions: Estimation of the δSPT during therapy expressed as change in concentration using simple methods based on the slope of the drra correlated well to changes by PLBA and CPT and should therefore be used both in clinical research and in practice.
Highlights
Some decades ago, most allergists used endpoint titration by intradermal skin testing as a measure of skin reactivity
The simplified methods B2 and C2 correlated to the gold standard method A4 (r>0.75; P
This study shows that the two simple methods used for estimating changes in skin reactivity during subcutaneous immunotherapy trials (SCIT) correlate well with the gold standard, Parallel line bioassay (PLBA)
Summary
Most allergists used endpoint titration by intradermal skin testing as a measure of skin reactivity. Since results have been reported in terms of wheal diameter, or in some scientific reports in terms of wheal area. It has not been possible to compare changes in skin test wheal sizes with that of bronchial, nasal or conjunctival provocation test threshold concentrations. Due to the flat allergen wheal dose response [1,2,3,4], a 10-fold increase in skin sensitivity roughly corresponds to an increase in wheal diameter from 3 mm to 4.65 mm, Immunother Open Acc, an open access journal ISSN:2471-9552. Parallel line bioassay (PLBA) has been acknowledged to be the gold standard for estimation of changes in reactivity, e.g., in RAST and ELISA inhibition tests
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