EFFECT OF DILUTION, TEMPERATURE, AND PRESERVATIVES ON THE LONG-TERM STABILITY OF STANDARDIZED INHALANT ALLERGEN EXTRACTS

Background: Although documented stability of allergens used for diagno sis is important, research in this area has been limited. Most studies on extract stability have been of limited duration and discrepancies have been reported between stability test results of in vivo and in vi tro methods. Objective: In this study we determined the stability of a llergenic extracts, comparing the intracutaneous test and enzymallergo sorbent test inhibition method and determining the effect of temperatu re, dilution, and preservatives. Methods: Three formulations of timoth y pollen, birch pollen, house dust mite (D. pteronyssinus) and cat dan der extracts, as used for bronchoprovocation, skin prick testing and i ntracutaneous testing, were stored for 24 months at 6 degrees C. The i nfluence of temperature on various formulations was determined using t he enzymallergosorbent test inhibition technique during storage for up to 36 months. Results: Most formulations were found to be stable for 24 (intracutaneous test) or 36 (enzymalrergosorbent test inhibition) m onths at 6 degrees C. At 25 degrees C, most formulations showed a decr ease in relative potency, which remained above the limit of 0.3 times the in-house-reference for the bronchoprovocation formulation of timot hy pollen, birch pollen, and house dust mite and for the skin prick te st formulation of cat dander. Conclusions: Cat dander was remarkably s table at 6 and 25 degrees C in glycerine and birch pollen was very sus ceptible to phenol. This destructive effect of phenol could be prevent ed by adding human serum albumin. the discrepancy between in vivo and in vitro tests reported by others was confirmed for house dust mite an d timothy pollen.