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[Studies on antibiotic skin testing]
Y Matsumura1, M Shiga, K Setoyama
1Matsumura Clinic and Research Institute for Asthma and Immunological Diseases.
Abstract:
Commercially available antibiotics for injection are supplied with test ampules. Users are instructed to dissolve them to make 300 micrograms/ml solution for intradermal pretests to avoid allergic reactions. Sometimes this concentration is too low to prevent anaphylactic reactions. In the present study, we tried to find the maximum concentration for the intradermal tests which would have high sensitivity without giving nonspecific, false positive reactions. We investigated intradermal tests with cephalothin (CET) in a patient who suffered from anaphylaxis after drip infusion with CET, although she was judged to be negative to CET by the usual intradermal test prior to the infusion. Her CET skin test was negative at a concentration of 150 micrograms/ml and positive at 300 micrograms/ml 6 weeks after anaphylaxis, but negative at 300 micrograms/ml and positive at 1000 micrograms/ml 4 and 7 years after anaphylaxis. Prick tests were always negative, even with the maximum soluble concentration of CET, 200 mg/ml. Nonspecific reactions to intradermal tests at concentrations as high as 1000 micrograms/ml were examined with 20 kinds of penicillins and cephems in 51 healthy subjects without histories of drug allergies. Very few false positive reactions were observed, except in 5 out of 24 cases with cefotiam. Intradermal tests at 3000 micrograms/ml, however, frequently resulted in nonspecific reactions. We conclude that 1000 micrograms/ml, not 300 micrograms/ml solutions should be used for intradermal tests to prevent allergic reactions to the injection of antibiotics.
Insights
Higher concentrations of cephalothin (CET) intradermal tests are needed to accurately detect antibiotic allergies. A 1000 micrograms/ml solution is recommended over the standard 300 micrograms/ml to prevent false negatives and ensure patient safety.
Area of Science:
- Pharmacology
- Allergy and Immunology
- Clinical Diagnostics
Context:
- Standard antibiotic injection protocols include intradermal pretests using 300 micrograms/ml solutions to screen for allergic reactions.
- This standard concentration is sometimes insufficient, leading to potential anaphylaxis in patients who test negative.
- A case study involving cephalothin (CET) demonstrated evolving skin test sensitivity post-anaphylaxis.
Purpose:
- To determine the optimal concentration for intradermal antibiotic testing that maximizes sensitivity while minimizing false positives.
- To evaluate the safety and efficacy of higher concentration intradermal tests for detecting antibiotic hypersensitivity.
Summary:
- Intradermal testing with cephalothin (CET) showed a patient's sensitivity increased from 300 micrograms/ml to 1000 micrograms/ml over time post-anaphylaxis.
- Prick tests remained negative even at maximum soluble CET concentrations.
- Higher concentrations (up to 1000 micrograms/ml) of various penicillins and cephems showed minimal nonspecific reactions in healthy subjects, unlike 3000 micrograms/ml.
Impact:
- Recommends increasing intradermal test concentrations to 1000 micrograms/ml for improved accuracy in preventing antibiotic-induced allergic reactions.
- Highlights the need for revised diagnostic guidelines for antibiotic hypersensitivity testing.
- Enhances patient safety by reducing the risk of undetected allergies and subsequent anaphylaxis.