[Test of human basophil degranulation. The interpretation and analysis of variability factors in the absence of antigen].
The human basophil degranulation test (TDBH) is performed using a concentrated cell suspension enriched for polymorphonuclear basophils. This preparation is placed in wells on a glass slide with an allergen solution of decreasing concentration. After incubation the cells are fixed in the wells and stained with toluidine blue. Preparations containing fewer metachromatic basophils than in control preparation of the same cell suspension without antigen contain degranulated basophils and in this way a degranulation index can be calculated. By considering the variability in the number of basophils between duplicate control wells from the same cell suspension, it can be shown that the test can be considered to be positive only if the number of degranulated basophils equals or exceeds 50% of the total number of basophils. This variance can be attributed to the subjectivity of the reader, and to differences in the differential cell counts from well to well. On the other hand, the presence of atopic allergy had no effect on the basophil counts.