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 D2 (PGD2) during sting challenge were studied in relation to clinical symptoms. Prechallenge levels (mean +/- SD) of histamine, tryptase, and PGD2 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 PGD2 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.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonisotopic binding assay for measuring vitamin B12 and folate in serum.

We evaluated a nonisotopic method (CEDIA; cloned enzyme donor immunoassay) for estimating vitamin B12 and folate in serum. The assays were performed with a Cobas-Mira analyzer. Intra-assay CVs were from 3.7% to 11.0% for vitamin B12 and from 1.2% to 10.7% for folate. Interassay CVs ranged from 9.5% to 11.9% for vitamin B12 and from 6.1% to 18.5% for folate. Linearity was satisfactory, with analytical recovery of 94% at 8.7 and 25.4 nmol/L for folate and 280 and 554 pmol/L for vitamin B12. The detection limit was 3.6 nmol/L for folate and 12.3 pmol/L for vitamin B12. Results of this assay correlated well with those of a conventional radioassay: r = 0.98 for vitamin B12 (n = 51) and r = 0.97 for folate (n = 57). The CEDIA was easy to perform but appeared to be unreliable for use with samples from myeloma patients.