Positive serum specific IgE has a short half-life in patients with penicillin allergy and reversal does not always indicate tolerance

Table 3 Specific IgE level (positive/negative) compared to outcome of penicillin challenge (positive/negative)

		I.v/single p.o (pen V,G) (n = 21)**		P.o.7 (pen V) (n = 15)*		Single p.o (other) (n = 8)*		P.o.7 (other) (n = 8)*
		Pos (n = 2)	Neg (n = 19)	Pos (n = 2)	Neg (n = 13)	Pos (n = 1)	Neg (n = 7)	Pos (n = 1)	Neg (n = 7)
Post-challenge s-IgE	Pos (n = 11)	1	3	1	5	1**	0	0	0
	Neg (n = 25)	1	11*	1	4	0	4	1	4*
	NT (n = 12)	0	5	0	4	0	3	0	3

A total of 21 patients were challenged with i.v/single p.o pen V, followed by p.o.7 pen V in 15 patients. **Patient no. 5 (Table 1) was only challenged with culprit drug (DX).
Nine patients also challenged with other drug (either their culprit drug or because of previous positive specific IgE to AMP or AX). In 8 cases initiated by single p.o, and in 1 case* (no. 17, Table 1) initiated by challenge with pen G and V (i.v/single p.o), followed by challenge with AX (culprit drug) in p.o.7 (not preceded by single p.o AX). No. 17, Table 1 had not performed p.o.7 with pen V.
s-IgE: serum specific IgE to penicillin, I.v: intravenous, Single p.o: single dose oral challenge, P.o.7: 7-day oral challenge, Pen V: phenoxymethylpenicillin, Pen G: benzylpenicillin, DX: dicloxacillin, AX: amocxicillin, Pos: positive, Neg: negative, NT: not tested.

ISSN: 2045-7022