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Minor Determinants of Penicillin and Amoxicillin Are Still Key Components of Penicillin Skin Testing
Dayne Voelker1, Mitchell Pitlick1, Alexei Gonzalez-Estrada2
1Mayo Clinic School of Graduate Medical Education, Mayo Clinic, Rochester, Minn.
Background:
The positive rate and pattern of penicillin skin test (PST) has been reported to be decreasing and changing. Previous studies differ about which penicillin component is the dominant component in positive PST result.
Objective:
To characterize past and current PST patterns to determine whether different determinants in PST have changed over time.
Methods:
A retrospective review of electronic medical records (January 2001-December 2017) was performed for patients who underwent PST. Data were divided into 4 cohorts to see whether trends occurred over time. The cohorts were divided as follows: cohort 1 (2001-2005), cohort 2 (2006-2010), cohort 3 (2011-2015), and cohort 4 (2016-2017).
Results:
A total of 30,883 patients underwent PST with the following breakdowns per cohort: cohort 1, 6,536; cohort 2, 10,372; cohort 3, 10,640; and cohort 4, 3,335. Of these, 329 patients (1.0%) had a positive PST result with a wheal of 3 × 3 mm or greater, with 110 in cohort 1, 130 in cohort 2, 67 in cohort 3, and 22 in cohort 4, whereas 170 patients (0.5%) had a positive PST result with a wheal of 5 × 5 mm or greater, with 54 in cohort 1, 72 in cohort 2, 34 in cohort 3, and 10 in cohort 4. When the positive PST rates of cohort 2 (1.25%), cohort 3 (0.6%), and cohort 4 (0.6%) were compared with those of cohort 1 (1.7%), there was a significant decrease in positive PST rates (P = .0278; P < .0001; P < .0001, respectively). When cohort 1 positive rate to benzylpenicillin polylysine among the positive PST (wheal of 3 × 3 mm or greater) was compared with those of the other cohorts (cohorts 2-4), the percent positive of benzylpenicillin polylysine in PST was 27% compared with 21% (P = .38), 34% (P = .5), and 18% (P = .6), respectively. When the positive PST result was defined as a wheal of 5 × 5 mm or greater, the positive rate for benzylpenicillin polylysine in PST increased over time (cohort 2: 22%, P = .8; cohort 3: 32%, P = .3; cohort 4: 40%, P = .264) compared with cohort 1 (19%).
Conclusions:
Positive PST rate is decreasing. We demonstrate that despite benzylpenicillin polylysine solely positive rates remaining relatively stable, the minor penicillin determinants and amoxicillin play an important role in PST and their adoption into standard protocol for routine PST should be considered.
Insights
The positive rate of penicillin skin testing (PST) has significantly decreased over time. While benzylpenicillin polylysine results remained stable, minor determinants and amoxicillin are increasingly important in positive PST results.
Area of Science:
- Immunology
- Dermatology
- Pharmacology
Background:
- The positive rate and patterns of penicillin skin tests (PST) are reportedly decreasing and changing.
- Previous research shows conflicting results regarding the dominant component in positive PST results.
Purpose of the Study:
- To analyze historical and current PST patterns.
- To determine if different determinants in PST have evolved over time.
Main Methods:
- Retrospective review of electronic medical records from January 2001 to December 2017.
- Patients undergoing PST were divided into four cohorts based on time periods: 2001-2005, 2006-2010, 2011-2015, and 2016-2017.
- Analysis of positive PST rates and specific determinant reactivity across cohorts.
Main Results:
- A total of 30,883 patients underwent PST.
- The overall positive PST rate (wheal ≥ 3x3 mm) decreased significantly from 1.7% in cohort 1 (2001-2005) to 0.6% in cohorts 3 (2011-2015) and 4 (2016-2017).
- While benzylpenicillin polylysine positivity remained relatively stable (19-34%), positivity for minor determinants and amoxicillin increased over time, particularly when a 5x5 mm wheal was considered positive.
Conclusions:
- The overall positive penicillin skin test rate is declining.
- Minor penicillin determinants and amoxicillin are increasingly significant in positive PST results.
- Consideration should be given to incorporating these minor determinants and amoxicillin into standard PST protocols.
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