The very limited usefulness of skin testing with penicilloyl-polylysine and the minor determinant mixture in evaluating nonimmediate reactions to penicillins.

BACKGROUND

The contribution of skin testing with penicilloyl-polylysine (PPL) and the minor determinant mixture (MDM) to the diagnosis of hypersensitivity reactions to penicillins differs greatly according to the type of reaction: immediate (occurring within 1 h after the last drug administration) or nonimmediate (occurring more than 1 h after the last drug administration).

OBJECTIVE

To assess the contribution of skin testing with PPL and MDM to the diagnosis of nonimmediate reactions to penicillins.

METHODS

We evaluated 162 adults who had had 232 nonimmediate reactions to penicillins, mostly aminopenicillins, and presented positive skin and/or patch tests to one or more penicillin reagents: PPL, MDM, benzylpenicillin, ampicillin, and amoxicillin, as well as any responsible penicillins.

RESULTS

A total of 157 subjects (96.9%) displayed patch-test and/or delayed-reading intradermal-test positivity to penicillin reagents, which indicates a cell-mediated hypersensitivity; six of them also presented immediate-reading skin-test positivities. All 157 patients with a cell-mediated hypersensitivity were positive to the responsible penicillins (parent drugs); 16 of them also displayed delayed-reading intradermal-test positivity to MDM. Five (3.1%) of the 162 patients displayed only immediate-reading skin-test positivity (four to PPL and one to amoxicillin). Overall, 158 subjects (97.5%) presented positive responses to the responsible penicillins, while only 9 (5.5%) and 17 (10.5%) were positive to PPL and MDM, respectively.

CONCLUSIONS

The contribution of skin testing with PPL and MDM in diagnosing nonimmediate hypersensitivity reactions to penicillins, especially cell-mediated ones, is very limited. This finding could be useful at a time when PPL and MDM are not available in all countries.