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Table 2 Statistical analysis plan

From: Comparing short to standard duration of antibiotic therapy for patients hospitalized with cellulitis (DANCE): study protocol for a randomized controlled trial

Variable/outcome Hypothesis Outcome measure Methods of analysis
1. Primary    
Resolution without relapse Intervention not inferior to control Percent cured on day 14 without relapse by day 28 [binary] Absolute risk difference
2. Secondary    
Relapse by day 90 No difference Percent with relapse [binary] Chi2 ➔ Relative risk
Time to relapse No difference Relapse after cure [time to event] Kaplan-Meier survival analysis
Objective speed of recovery No difference Cellulitis severity score [continuous] Student’s T-test or Mann–Whitney U test
Subjective speed of recovery No difference Visual analogue scales of pain and swelling [continuous] Student’s T-test or Mann–Whitney U test
Quality of life No difference SF-36 questionnaire score at day 1, 28 and 90 [continuous] Student’s T-test or Mann–Whitney U test
Additional antibiotic usage No difference Total amount of additional antibiotic use, in DDD [continuous] Student’s T-test or Mann–Whitney U test
Health care utilization No difference Total treatment associated costs, Health Care Utilization Questionnaire [continuous] Student’s T-test or Mann–Whitney U test
3. Subgroup analyses    
Cellulitis severity score on a continuous scale Severity score affects cure rate   Regression analysis, with interaction term for severity score
Diabetes mellitus vs no diabetes mellitus Diabetes affects cure rate   Regression analysis, with interaction term for (no) diabetes
4. Sensitivity analyses Intervention not inferior to control All outcomes  
Per protocol analysis    Chi2 ➔ Relative risk
Primary outcome adjusted for covariates    Logistic regression analysis