Elective Penicillin Skin Testing

8/14/2019 Elective Penicillin Skin Testing

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Elective PCN Skin Testing vs.

PCN Skin Testing at Time of Need

Timothy J. Sullivan, M.D.


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Elective Penicillin Skin Testing

Skin testing with a full battery of penicillin Greagents will detect nearly all penicillin G or Vallergic patients ~2% chance of urticaria within 48 hours in skin

test negative patients

~0.1% chance of anaphylaxis in skin test negative

patients No convincing evidence skin tests sensitize or re-

sensitization


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Elective Skin Testing for IgE to

Sulfamethoxazole

Skin testing with Sulfamethoxazoyl poly-

tyrosine can detect nearly all patients whoexpress IgE to sulfamethoxazole

Reagent must be synthesized within ~1

month of use in a well equipped laboratory

If you do not have the reagent, you can not

do the test


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Skin Testing To Detect Penicillin AllergySullivan et.al. 1981. JACI 68:171-180.

A study of 469 skin test positive patients

Penicilloyl-Poly-L-Lysine positive 76%

PPL +/or Pen G positive 93%

Penicilloate alone positive 7%


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Skin Test For Diagnosis of Penicillin AllergyRessler, Mendelson. 1987. Ann Allergy 59:167-170.

Review including 7 studies in addition to ours

using full batteries of minor determinantreagents Patients reacting only to minor determinant

antigens ranged from 13% to 35% with an

average of 25% Relying on PPL to detect IgE to penicillin would

be expected to miss ~25% of allergic patients


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Elective Penicillin G Skin Testing

Testing with PPL alone will miss ~25% of

allergic subjects Testing with PPL and Pen G will miss ~7%

Testing with PPL and Pen G and PA will

detect nearly all the remainder who would

react to penicillin G or V


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PCN Skin Tests in 740 Hx+ Patients

Relation to time since reaction

0

20

40

60

80

100

0-6 Mos 6-12 Mos 1-5 Years 5-10 Years >10 Years

Time after allergic reaction to penicillin

%

Posi t

ive

Sullivan et. al. 1981. JACI 68:171-180


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PCN Skin Tests

Relation to time since reaction

Skin testing too early can result in false

negative results Patients skin test positive now may well be

skin test negative when a need for penicillin

arises sometime in the future. Another skin

test at the time of need would be needed toprevent useless avoidance.


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Penicillins

Pen G Ampicillin

AmoxicillinPen V

Piperacillin

Ticarcillin


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Penicillin Allergy

Early studies of skin testing to detect IgE to

penicillin: Penicillin G or V sensitization

Penicillin G skin test reagents

Penicillin G or V therapy

2010 Penicillin Allergy Amoxicillin sensitization

Penicillin G skin test reagents

Amoxicillin therapy


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Penicillin G vs. Amoxicillin

Amoxicillin differs frompenicillin G by having a

charged free aminogroup and a hydroxylgroup in the side chain

Immune responses tohaptens formed fromthese two parentmolecules do notalways cross react

Penicillin G

Amoxicillin


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IgE to Amoxicillin may not be detected

by Penicillin G reagents

Studies of patients sensitized by amoxicillin, testedwith penicillin G and amoxicillin reagents, and

challenged with amoxicillin are sparse. In vitro assays of IgE specificity with specific

inhibition show AMX specific IgE can be presentalone or concurrent with crossreactive IgE (Antunezet.al. 2006. Allergy 61:940-946. And Sullivanunpublished data.)

Full value of AMX skin tests to detect these patientsnot yet clear.


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Elective Penicillin G Skin Testing

Pitfalls

Testing too early

Original immunologic sin was amoxicillin andthe drug needed is amoxicillin

Interval administration of cross reacting

drugs (e.g. Cephalexin, Cefaclor)

Re-sensitization by a subsequent course of a

penicillin


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Resensitization by Penicillin Therapy

High dose 6 weeks of therapy for SBE or

osteomyelitis 60% (6 of 10) re-sensitized(Earl & Sullivan)

Hx+, previously ST+, now ST-, treated: 22%

resensitized (Polmar)

Liberal Hx+, ST-, treated:


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A&I Physicians & Penicillin Allergic Patients

Consultation or Technical Support

Accurate diagnosis

Treatment of conditions disposing to need forantibiotics (e.g. allergic rhinitis)Use of alternative classes of medications.Updated drug exposure information

Assessment of current drug allergy statusDesensitization if needed Treating through reactions


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Elective PCN Skin Testing vs.

PCN Skin Testing at Time of Need

Elective PCN skin testing can be an excellentcommunity or institutional resource Patient and Primary Physician knowledge

essential to effective use of the information

Effective management of drug allergicpatients is best achieved by expertconsultation

An A&I physician is more important than areadily available test without context

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Elective Penicillin Skin Testing