title: Diagnosing nonimmediate reactions to penicillins by in vivo tests.
abstract: BACKGROUND
  Maculopapular and urticarial rashes are nonimmediate manifestations common during penicillin treatment; the former often represent cell-mediated hypersensitivity. Our objectives were to assess the incidence of allergy in adults reporting nonimmediate manifestations during penicillin therapy and to evaluate the diagnostic potential of patch tests, delayed-reading skin tests and challenges in such cases.
  
  
  METHODS
  We used prick and intradermal tests as well as patch tests with penicillin determinants, ampicillin, amoxicillin and any other suspect penicillins. We also performed challenges with the suspect antibiotics.
  
  
  RESULTS
  Such antibiotics were aminopenicillins in 93.1% of 259 patients, most of whom had suffered from maculopapular rashes followed by piperacillin (4.2%). Three subjects displayed immediate skin test positivity. Ninety-four subjects showed patch test and delayed intradermal test positivity to the culprit penicillin (90 to aminopenicillins and 4 to piperacillin) and were considered as having had delayed hypersensitivity reactions. Five of the 8 subjects who displayed delayed intradermal test positivity and patch test negativity to the suspect penicillin underwent challenges, 2 reacted positively to the responsible aminopenicillin. Among the remaining 154 with negative results in allergologic tests, 125 agreed to undergo challenges; only 3 reacted. In all, 98 patients -- 93 of whom had experienced maculopapular rashes -- displayed delayed hypersensitivity (94 to aminopenicillins and 4 to piperacillin).
  
  
  CONCLUSIONS
  Both patch and intradermal tests are useful in evaluating nonimmediate reactions to penicillins, particularly maculopapular rashes. Patch test and delayed intradermal positivity together indicate delayed hypersensitivity. Intradermal testing appears to be slightly more sensitive than patch testing.
authors.affiliation: Department of Internal Medicine and Geriatrics, UCSC Allergy Unit, Complesso Integrato Columbus, Rome, Italy. columbus.allerg@linet.it
authors.forename: Antonio
authors.initials: A
authors.lastname: Romano
authors.forename: Marinella
authors.initials: M
authors.lastname: Viola
authors.forename: Chiara
authors.initials: C
authors.lastname: Mondino
authors.forename: Rosa
authors.initials: R
authors.lastname: Pettinato
authors.forename: Maina
authors.initials: M
authors.lastname: Di Fonso
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Papa
authors.forename: Alberto
authors.initials: A
authors.lastname: Venuti
authors.forename: Paolo
authors.initials: P
authors.lastname: Montuschi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004342:Drug Hypersensitivity / Q000175:diagnosis* / Q000276:immunology; D005260:Female; D006801:Humans; D006968:Hypersensitivity, Delayed / Q000175:diagnosis* / Q000276:immunology; D007428:Intradermal Tests / Q000592:standards; D008297:Male; D008875:Middle Aged; D010328:Patch Tests / Q000592:standards; D010406:Penicillins / Q000009:adverse effects* / Q000276:immunology
chemical_list: D010406:Penicillins