Development of allergen-coated paper discs for allergy diagnosis by ELISA

In vitro testing is useful for detecting pollen and fungal-allergen sensitivities in nasobronchial-allergy patients. However, allergen-coated discs or solid-phases supplied in kits do not contain all the relevant extracts. The present study was aimed to develop a safe and credible procedure of allergen coating on paper discs for allergy diagnosis by ELISA. Paper discs were coated with indigenous allergens using poly(vinyl alcohol) and glutaraldehyde. ELISAs were carried out to standardize the allergen-coated discs using skin-test-positive-patients' sera. The cut-off value (A) for ELISA was worked out by analysing normal human sera (NHS) and is based on the mean+/-2 S.D. for the NHS value. The allergen-coated discs, i.e. Centre for Biochemical Technology (CBT) discs, demonstrated excellent comparison with plate-binding method and Pharmacia discs [Prosopis juliflora (mesquite), critical value 0.879 at 5% probability+/-0.599, n=11, is significant]. Inter- and Intra-assay coefficients of variations ranged from 2.5-14.05% to 4. 8-11.5% with different allergens. Results of skin tests and ELISA with CBT discs showed 60-70% correlation.