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Table 2 CDI-DaySyms™ PRO questionnaire item performance – Day 1

From: Clostridium difficile Infection–Daily Symptoms (CDI-DaySyms™) questionnaire: psychometric characteristics and responder thresholds

Item Score, mean (SD) at Day 1 Floor effects at Day 1, % Ceiling effects at Day 1, % High correlations > 0.80 with Low correlations < 0.20 with Clinical input/Rationale for decision Item decision
1. Diarrhea 2.4 (1.2) 8.9 16.1 Passing gas Predominant symptom in CDI Retain
2. Need to empty bowels right away 2.4 (1.2) 8.9 14.3 Bathroom more than usual Passing gas Describes intensity of urgency of bowel movements Retain
3. Need to go to the bathroom more than usual 2.4 (1.2) 11.4 13.8 Need to empty bowels Describes frequency of bowel movements Retain
4.Passing gas (flatulence) 1.6 (1.1) 17.6 6.1 Diarrhea, empty bowels, feeling tired, lack of energy, lightheadedness, dizziness, appetite Misfit/multidimensionality in Rasch analyses Delete
5. Abdominal cramping 1.8 (1.3) 22.6 10.7 Abdominal pain According to experts, pathophysiology is different from item 6 Retain
6. Abdominal pain 1.7 (1.3) 22.9 10.8 Abdominal cramping See item 5 Retain
7. Feeling bloated 1.3 (1.3) 38.8 6.7 Most patients do complain of bloating based on expert input Retain
8.Feeling tired 2.2 (1.1) 9.5 13.1 Lack of energy Passing gas Based on qualitative study, items 8 and 9 are different Retain
9.Lack of energy 2.2 (1.2) 10.1 13.7 Feeling tired Passing gas See item 8 Retain
10. Lightheadedness 1.0 (1.2) 44.8 5.5 Passing gas Experts considered lightheadedness more relevant to CDI than dizziness Retain
11. Dizziness 0.7 (1.1) 58.5 3.7 Passing gas See item 10 Delete
12. Lack of appetite 1.6 (1.3) 26.9 11.4 Passing gas Experts noted that lack of appetite is relevant in severe disease Retain
13. Nausea 0.9 (1.2) 53.0 6.0 The item had a low mean score and high floor effect across patients Delete
  1. CDI Clostridium difficile infection, CDI-DaySyms™ Clostridium difficile infection–daily symptoms, SD standard deviation