Table 2.
| Table 2a. Subgroup Analysis of Clinical Cure* Rates Through 7–14 days for Participants with a Drained Skin Abscess Treated with Trimethoprim-Sulfamethoxazole or Placebo by Presence or Absence of High-Risk Conditions. | |||
|---|---|---|---|
| Condition | Cure (n/total no. [%]) | Difference (95% CI) | |
| Trimethoprim- sulfamethoxazole | Placebo | ||
| Abscess cavity ≥5 cm | 69/77 (89.6) | 54/71 (76.1) | 14.7 (1.4 – 28.1) |
| Abscess cavity <5 cm† | 418/446 (93.7) | 403/462 (87.2) | 6.1 (2.1 – 10.1) |
| Erythema ≥5 cm | 357/390 (91.5) | 338/399 (84.7) | 6.8 (2.1 – 11.6) |
| Erythema <5 cm† | 130/134 (97.0) | 119/134 (88.8) | 8.2 (1.4 – 15.0) |
| History of MRSA infection | 43/45 (95.6) | 32/40 (80.0) | 15.6 (−0.6 – 31.7) |
| No history of MRSA infection | 444/479 (92.7) | 425/493 (86.2) | 6.5 (2.4 – 10.5) |
| Fever‡ | 93/102 (91.2) | 78/98 (79.6) | 14.3 (3.7 – 24.9) |
| No fever | 391/418 (93.5) | 374/430 (87.0) | 5.9 (1.7 – 10.1) |
| Diabetes | 50/58 (86.2) | 47/57 (82.5) | 3.8 (−11.3 – 18.8) |
| No diabetes | 437/466 (93.8) | 410/476 (86.1) | 7.6 (3.6 – 11.7) |
| Co-morbidity§ | 83/92 (90.2) | 73/88 (83.0) | 8.4 (−2.8 – 19.6) |
| No co-morbidity | 404/432 (93.5) | 384/445 (86.3) | 7.0 (2.8 – 11.2) |
| MRSA|| | 203/219 (92.7) | 202/249 (81.1) | 11.6 (5.2 – 18.0) |
| MSSA | 78/86 (90.7) | 71/86 (82.6) | 8.1 (−3.1 – 19.4) |
| No MRSA or MSSA | 203/216 (94.0) | 181/195 (92.8) | 1.2 (−4.1 – 6.5) |
| Table 2b. Subgroup Analysis of Composite Cure* Rates Through 7–14 days Among Participants with a Drained Skin Abscess Treated with Trimethoprim-Sulfamethoxazole or Placebo by Presence or Absence of High-Risk Conditions. | |||
|---|---|---|---|
| Condition | Cure (n/total no. [%]) | Difference (95% CI) | |
| Trimethoprim- sulfamethoxazole | Placebo | ||
| Abscess cavity ≥5 cm | 62/77 (80.5) | 51/71 (71.8) | 8.5 (−6.3 – 23.4) |
| Abscess cavity <5 cm† | 391/446 (87.7) | 345/462 (74.7) | 12.2 (7.0 – 17.4) |
| Erythema ≥5 cm | 335/390 (85.9) | 295/399 (73.9) | 11.5 (5.7 – 17.2) |
| Erythema <5 cm† | 118/134 (88.1) | 101/134 (75.4) | 11.9 (2.1 – 21.8) |
| History of MRSA infection | 40/45 (88.9) | 24/40 (60.0) | 28.9 (8.8 – 49.0) |
| No history of MRSA infection | 413/479 (86.2) | 372/493 (75.5) | 10.2 (5.1 – 15.2) |
| Fever‡ | 83/102 (81.4) | 64/98 (65.3) | 18.4 (5.4 – 31.3) |
| No fever | 368/418 (88.0) | 329/430 (76.5) | 10.2 (4.9 – 15.5) |
| Diabetes | 44/58 (75.9) | 36/57 (63.2) | 10.9 (−7.4 – 29.3) |
| No diabetes | 409/466 (87.8) | 360/476 (75.6) | 11.7 (6.7 – 16.8) |
| Co-morbidity§ | 71/92 (77.2) | 55/88 (62.5) | 13.5 (−0.8 – 27.9) |
| No co-morbidity | 382/432 (88.4) | 341/445 (76.6) | 11.3 (6.2 – 16.5) |
| MRSA|| | 186/219 (84.9) | 163/249 (65.5) | 18.3 (10.3 – 26.2) |
| MSSA | 72/86 (83.7) | 63/86 (73.3) | 10.5 (−2.9 – 23.8) |
| No MRSA or MSSA | 192/216 (88.9) | 167/195 (85.6) | 3.24 (−3.7 – 10.2) |
| Table 2c. Subgroup Analysis of Composite Cure* Rates Through 42–56 days Among Participants with a Drained Skin Abscess Treated with Trimethoprim-Sulfamethoxazole or Placebo by Presence or Absence of High-Risk Conditions. | |||
|---|---|---|---|
| Condition | Cure (n/total no. [%]) | Difference (95% CI) | |
| Trimethoprim-sulfamethoxazole | Placebo | ||
| Abscess cavity ≥5 cm | 55/70 (78.6) | 47/70 (67.1) | 11.4 (−4.61 – 27.5) |
| Abscess cavity <5 cm† | 361/434 (83.2) | 311/440 (70.7) | 12.5 (6.75 – 18.2) |
| Erythema >5 cm | 307/376 (81.6) | 269/383 (70.2) | 11.4 (5.13 – 17.7) |
| Erythema <5 cm† | 109/129 (84.5) | 89/127 (70.1) | 14.4 (3.51 – 25.3) |
| History of MRSA infection | 33/43 (76.7) | 21/39 (53.8) | 22.9 (0.34 – 45.4) |
| No history of MRSA infection | 383/462 (82.9) | 337/471 (71.5) | 11.4 (5.81 – 16.9) |
| Fever‡ | 76/98 (77.6) | 57/94 (60.6) | 16.9 (2.99 – 30.8) |
| No fever | 338/403 (83.9) | 299/412 (72.6) | 11.3 (5.44 – 17.2) |
| Diabetes | 38/56 (67.9) | 36/56 (64.3) | 3.57 (−15.7 – 22.9) |
| No diabetes | 378/449 (84.2) | 322/454 (70.9) | 13.3 (7.67 – 18.9) |
| Co-morbidity§ | 61/88 (69.3) | 54/86 (62.8) | 6.53 (−8.7 – 21.7) |
| No co-morbidity | 355/417 (85.1) | 304/424 (71.7) | 13.4 (7.71 – 19.2) |
| MRSA|| | 166/208 (79.8) | 139/235 (59.2) | 20.7 (11.9 – 29.4) |
| MSSA | 71/85 (83.5) | 57/82 (69.5) | 14.0 (0.11 – 27.9) |
| No MRSA or MSSA | 176/209 (84.2) | 160/190 (84.2) | 0.0 (−7.71 – 7.71) |
Abbreviations: MRSA = methicillin-resistant Staphylococcus aureus; MSSA = methicillin-susceptible S. aureus
Overall, for trimethoprim-sulfamethoxazole and placebo groups, clinical cure rate at 7–14 days was 92.9% and 85.7% (difference, 7.2; 95% CI 3.2–11.2), composite cure rate at 7–14 was 86.5% and 74.3% (difference, 12.2; 95% CI 7.2–17.1) and extended composite cure at 42–56 days was 82.4% and 70.2% (difference, 12.2; 95% CI 6.8–17.6), respectively. Outcomes were defined as follows: clinical cure was defined as resolution of all symptoms and signs of infection, or improvement such that no new antibiotics were prescribed (through 7–14 days after the end of treatment); composite cure was defined as resolution of all symptoms and signs of infection, or improvement such that no additional antibiotics and/or surgical drainage procedure were required (through 7–14 days and 42–56 days after the end of treatment).
Abscess cavity and erythema dimensions were defined as the maximal dimension (length or width).
Fever was defined as history of fever within the preceding week or temperature >38°C measured in the ED (0.8%).
Co-morbidities were defined as those present in >0.5% of study participants: diabetes (10.9%); eczema or other chronic skin condition (3.4%); chronic obstructive pulmonary disease (1.1%); congestive heart failure (0.9%); human immunodeficiency virus infection (1.6%); and cancer (0.9%).
Culture results were those based on the organism isolated from primary wound specimen.