Table 1. Patient Demographic and Testing Characteristics of Trimethoprim-Sulfamethoxazole Allergy in Tested Derivation and Validation Cohortsa.
| Characteristic | Melbourne, Australia b | Nashville, Tennessee c | ||||
|---|---|---|---|---|---|---|
| Overall (N = 116) | Positive (n = 6) | Negative (n = 110) | Overall (N = 204) | Positive (n = 13) | Negative (n = 191) | |
| Age, median (IQR), y | 64 (54-74) | 54 (46-66) | 64 (54-75) | 62 (48-70) | 48 (13-61) | 62 (50-70) |
| Sex, No. (%) | ||||||
| Female | 72 (62.1) | 2 (33.3) | 70 (63.6) | 162 (79.4) | 11 (84.6) | 151 (79.1) |
| Male | 44 (37.9) | 4 (66.7) | 40 (36.4) | 42 (20.6) | 2 (15.4) | 40 (20.9) |
| Race and ethnicity, No. (%) | ||||||
| Asian | 6 (5) | NA | NA | 2 (1) | NA | NA |
| Black | 1 (1) | 9 (4) | ||||
| White | 104 (90) | 188 (92) | ||||
| Unknown | 5 (4) | 5 (2) | ||||
| Comorbidities, No. (%) | ||||||
| HIV | 0 | NA | NA | 9 (4.4) | NA | NA |
| Diabetes | 5 (4.3) | 38 (18.6) | ||||
| Transplant | 18 (15.5) | 17 (8.3) | ||||
| Immunocompromised (other than HIV or transplant) | 59 (50.9) | NA | ||||
| PEN-FAST components, No. (%) | ||||||
| Treatment required | 9 (7.8) | 5 (83.3) | 4 (3.6) | 21 (10.3) | 5 (38.5) | 16 (8.4) |
| Anaphylaxis, angioedema, or SCAR | 7 (6.0) | 2 (33.3) | 5 (4.5) | 40 (19.6) | 4 (30.8) | 36 (18.8) |
| Reaction within last 5 y | 57 (49.1) | 5 (83.3) | 52 (47.2) | 69 (33.8) | 8 (61.5) | 61 (31.9) |
| Allergy phenotype, No. (%) | ||||||
| Immediate | 32 (27.6) | 0 | 32 (29.1) | 23 (11.3) | 3 (23.1) | 20 (10.5) |
| Delayed | 41 (35.3) | 6 (100) | 35 (31.8) | 106 (52) | 9 (69.2) | 97 (50.8) |
| Unknown or otherd | 43 (37.1) | 0 | 43 (39.1) | 75 (36.8) | 1 (7.7) | 74 (38.7) |
| Allergy phenotype details, No. (%) | ||||||
| Childhood | 19 (16.4) | NA | NA | Unavailable | ||
| Diffuse rash | 57 (49.1) | |||||
| Urticaria | 6 (5.2) | |||||
| Unknown | 18 (15.5) | |||||
| Blistering or desquamation | 4 (3.4) | |||||
| Swelling | 4 (3.4) | |||||
| Respiratory compromise | 2 (1.7) | |||||
| Fever | 3 (2.6) | |||||
| Anaphylaxis | 1 (0.9) | |||||
| Testing method, No. (%) | ||||||
| PT | 16 (13.8) | 6 (100) | 10 (9.1) | 0 | 0 | 0 |
| OC | 111 (95.7) | 1 (16.7) | 110 (100) | 204 (100) | 13 (100) | 191 (100) |
| Positive PT result | 5/6 | 0 | ||||
| Positive OC resulte | 1/6 | 13/13 | ||||
| Immediate reaction to OC | NA | 0 | NA | NA | 7/13 | NA |
| Pruritus | 2/7 | |||||
| Urticaria | 2/7 | |||||
| Arm pain and malaise | 1/7 | |||||
| Fever | 1/7 | |||||
| Throat pruritus with chest tightness | 1/7 | |||||
| Delayed reaction to OC | NA | 1/1 | NA | NA | 6/13 | NA |
| Benign exanthem | 1/1 | 1/6 | ||||
| Erythema | 2/6 | |||||
| Urticaria | 1/6 | |||||
| Fever with myalgias and headache | 1/6 | |||||
| Fever with nausea and vomiting | 1/6 | |||||
Abbreviations: NA, not applicable; OC, oral challenge; PT, patch test; SCAR, severe cutaneous adverse reaction.
Includes specific antibiotic allergy label of Co-T or trimethoprim-sulfamethoxazole. Recent anaphylaxis was defined as anaphylaxis within the past 5 years; a positive allergy test result was defined as any positive allergy test finding, including positive result on patch testing or oral challenge.
Prospective cohort; Austin Health (87.1% [101 of 116]) and Peter MacCallum Cancer Centre (12.9% [15 of 116]); November 1, 2015, to July 31, 2022. Testing sites were inpatient and outpatient. Excluded phenotypes were recent anaphylaxis and SCAR. Patients underwent patch testing and oral challenge testing after patch testing.
Retrospective cohort; Vanderbilt University Medical Center; October 1, 2015, to February 28, 2019. Testing sites were outpatient only. Excluded phenotypes were recent anaphylaxis and SCAR. Patients underwent 1-step and 2-step oral challenge testing.
Includes nonimmune mediated and reactions with unknown timeline.
Most patients with positive test reported a “trimethoprim-sulfamethoxazole” allergy (6 of 6 in the Melborne cohort and 12 of 13 in the US cohort), while 1 patient reported “unspecified sulfa” allergy.