ToolsCalculators
Trimethoprim-Sulfamethoxazole Allergy Decision Rule (SULF-FAST)
Risk-stratifies reported TMP-SMX (sulfa) allergy to identify candidates for direct oral challenge.
Trimethoprim-Sulfamethoxazole Allergy Decision Rule (SULF-FAST)
Reaction occurred 5 years ago or less
Anaphylaxis/angioedema, or a severe cutaneous adverse reaction (e.g., SJS/TEN, DRESS)
Reaction required treatment (e.g., ED visit, hospitalisation, epinephrine, antihistamines, or steroids)
Result0 points
Low risk (<3 points): a direct oral challenge with TMP-SMX may be considered under appropriate observation and local protocol.
- SULF-FAST score
- 0 / 5
When to use
- Adults with a reported trimethoprim-sulfamethoxazole (sulfa) allergy label who are being considered for antibiotic stewardship-driven direct oral challenge.
Formula
Score = 2 (reaction 5 years ago or less) + 2 (anaphylaxis/angioedema OR severe cutaneous adverse reaction) + 1 (reaction required treatment). Range 0-5; score <3 = low risk.
Pearls and pitfalls
- SULF-FAST directly adapts the PEN-FAST penicillin-allergy decision rule's item weights and <3-point low-risk cutoff to TMP-SMX allergy.
- Patients with anaphylaxis within the past 5 years or a severe cutaneous adverse reaction should not undergo direct oral challenge regardless of total score.
References
- Waldron JL, Rose M, Vogrin S, Krantz MS, Bolotte R, Phillips EJ, Trubiano JA. Development and Validation of a Sulfa Antibiotic Allergy Clinical Decision Rule. JAMA Netw Open. 2023;6(6):e2316776.
- Trubiano JA, Vogrin S, Chua KYL, et al. Development and Validation of a Penicillin Allergy Clinical Decision Rule. JAMA Intern Med. 2020;180(5):745-52.