Insect-sting challenge in 138 patients: Relation between clinical severity of anaphylaxis and mast cell activation

One hundred thirty-eight patients with a previous anaphylactic reaction to a yellow jacket or a honeybee sting, as well as eight volunteers, were subjected to an in-hospital sting challenge. Plasma levels of histamine, tryptase, and prostaglandin D 2 (PGD 2) during sting challenge were studied in relation to clinical symptoms. Prechallenge levels (mean±SD) of histamine, tryptase, and PGD 2 were 2±1 nmol/L, 0.3±0.3 U/L, and 320±223 ng/L, respectively. In the volunteers and in none except for one of the nonreacting patients, these levels did not change significantly after challenge. In contrast, mean increases in the group of 18 patients with a mild reaction were significant for histamine and tryptase at one or more time points after the challenge. (Five patients demonstrated no increase in histamine; nine demonstrated no increase in tryptase.) Except for histamine levels in one patient, these increases were considerably more in all 17 patients with a severe reaction, starting from the first anaphylactic symptoms. Fifteen minutes later, peak values were reached of 1275±2994 nmol of histamine per liter (range, 3 to 12800 nmol/L; median, 11 nmol/L) and 406±1062 U of tryptase per liter (range, 1.8 to 4400 U/L; median, 17 U/L). This rise in levels inversely correlated with the mean arterial pressure. Plasma levels of PGD 2 in severely reacting patients did not differ significantly from those in patients with a mild or no reaction. In conclusion, only 28% of patients with a history of Hymenoptera anaphylaxis developed an anaphylactic reaction after an in-hospital challenge. The clinical severity of these reactions correlated with the level of systemically released, preformed histamine and tryptase, but not of PGD 2.