Table 2. FDSD acceptability, item discrimination, reliability, and known-groups analysis results (N=57).
| FDSD itema | Ceilingb n (%) | Floorb n (%) | Item discrimination indexc | Cronbach’s α (TSS; or on item removal) | Known groups (participant-reported severity)d Mean (s.d.) | Known groups (clinician-reported severity)e Mean (s.d.) |
|---|---|---|---|---|---|---|
| TSS (0–50) | — | — | — | 0.87 | Mild: 23.4 (9.86) Moderate: 24.6 (10.57) Severe: 30.8 (14.90) | Mild: 20.1 (9.54) Moderate: 27.4 (11.97) Severe: 29.3 (11.79) |
| 1. Stomach pain (0–10) | 3 (5.3%) | 3 (5.3%) | 0.40 | 0.84 | Mild: 4.1 (2.56) Moderate: 4.5 (2.31) Severe: 6.5 (2.99) | Mild: 3.8 (2.28) Moderate: 4.9 (2.76) Severe: 5.9 (2.51) |
| 2. Burning in the stomach (0–10) | 7 (12.3%) | 1 (1.8%) | 0.38 | 0.89 | Mild: 2.9 (2.69) Moderate: 4.6 (2.09) Severe: 5.8 (3.41) | Mild: 3.3 (2.44) Moderate: 4.9 (1.87) Severe: 5.4 (3.20) |
| 3. Nausea (0–10) | 13 (22.8%) | 2 (3.5%) | 0.08 | — | Mild: 3.3 (2.16) Moderate: 4.1 (3.31) Severe: 4.1 (3.38) | Mild: 3.3 (3.12) Moderate: 4.1 (3.19) Severe: 4.4 (3.13) |
| 4. Bloating (0–10) | 5 (8.8%) | 6 (10.5%) | 0.22 | 0.84 | Mild: 5.4 (2.59) Moderate: 5.2 (2.77) Severe: 6.0 (3.87) | Mild: 4.4 (2.47) Moderate: 6.2 (2.73) Severe: 5.6 (3.47) |
| 5. Stomach fullness (0–10) | 3 (5.3%) | 4 (7.0%) | 0.21 | 0.84 | Mild: 6.0 (2.31) Moderate: 5.6 (2.81) Severe: 6.5 (3.31) | Mild: 4.9 (2.18) Moderate: 5.9 (3.23) Severe: 6.6 (2.78) |
| 6. Early satiety (0–10) | 8 (14.0%) | 3 (5.3%) | 0.25 | 0.83 | Mild: 5.0 (2.75) Moderate: 4.8 (3.02) Severe: 6.0 (3.98) | Mild: 3.8 (2.61) Moderate: 5.6 (3.24) Severe: 5.8 (3.41) |
| 7. Burping/belching rating (0–10) | 4 (7.0%) | 4 (7.0%) | 0.23 | — | Mild: 3.9 (2.47) Moderate: 4.7 (2.49) Severe: 5.3 (3.82) | Mild: 3.3 (2.44) Moderate: 5.8 (2.36) Severe: 4.9 (3.15) |
| 8. Burping/belching bother (0–10) | 15 (26.3%) | 3 (5.3%) | 0.13 | — | Mild: 3.4 (2.80) Moderate: 4.1 (3.17) Severe: 4.7 (3.97) | Mild: 2.8 (2.79) Moderate: 4.8 (3.19) Severe: 4.7 (3.56) |
CRF, Case Report Form; DHIF, Demographic Health and Information Form; FD, functional dyspepsia; FDSD, Functional Dyspepsia Symptom Diary; TSS, Total Symptom Score.
FDSD items are scored on an 11-point numeric rating scale from 0 (no (concept)) to 10 (worst imaginable (concept)).
Floor and ceiling effects are represented by the percent of participants responding to the worst possible state/best possible state; in this instance, floor effect refers to a high percentage (≥25.0%) of participants selecting the score reflecting a state which cannot get any worse (i.e., 10, worst imaginable (concept)) and ceiling effect refers to a high percentage (≥25.0%) of participants selecting the score reflecting a state, which cannot get any better (i.e., 0, no (concept))(20, 21, 22).
Item discrimination index=proportion endorsed for severe group—proportion endorsed for mild/moderate group. The item discrimination index assesses the extent to which item responses accurately capture genuine patient experiences and are represented on a scale from 1 to −1, where negative or zero indices characterize poorly performing items and positive indices characterize well-performing items. Indices were evaluated using the following criterion: ≤0.20=poor performance, 0.21 to 0.29=moderate performance, 0.30 to 0.39=good performance, ≥0.40=excellent performance(23).
Participant-reported FD severity based on response in DHIF: mild n=10; moderate n=34; severe n=13.
Clinician-reported FD severity based on response in CRF: mild n=17; moderate n=20; severe n=20.