Background
Rasch analysis
Rasch analysis and painDETECT
Methods
Participants
Variables of interest
Person Variable | Coding | N** (%) |
---|---|---|
Age Sample mean age = 55.4 years Total N = 624 | Under 20 | 1 (0.2) |
20–29 years | 24 (3.8) | |
30–39 years | 43 (6.9) | |
40–49 years | 134 (21.5) | |
50–59 years | 199 (31.9) | |
60–69 years | 122 (19.6) | |
70–79 years | 73 (11.7) | |
80 plus | 28 (4.5) | |
Sex
| Male | 347 (55.6) |
Female | 277 (44.4) | |
NeP Diagnosis
| Chronic low back pain | 103 (16.5) |
Post-Diabetic peripheral neuralgia | 100 (16.0) | |
HIV related pain | 103 (16,5) | |
Chronic post-surgical pain | 106 (17.0) | |
Small fiber neuropathy | 110 (17.6) | |
Spinal cord injury | 97 (15.5) | |
SF12 PCS
Mean PCS = 31 (100 = perfect health) | 0–19 | 61 (10.0) |
20–39 | 446 (73.0) | |
40–59 | 102 (16.7) | |
60–79 | 2 (0.3) | |
80–100 | 0 | |
SF12 MCS
Mean MCS = 42.5 (100 = perfect health) | 0–19 | 22 (3.6) |
20–39 | 241 (39.4) | |
40–59 | 288 (47.1) | |
60–79 | 60 (9.8) | |
80–100 | 0 | |
BPI pain severity
Mean =5.2 | 0–3 Mild | 111 (18.1) |
4–6 Moderate | 297 (48.4) | |
7–10 Severe | 206 (33.6) | |
BPI pain interference
Mean = 5.6 | 0–3 Mild | 163 (26.2) |
4–6 Moderate | 244 (39.2) | |
7–10 Severe | 216 (34.7) |
Analysis plan
Results
Demographics
Analysis of 9 item PD-Q
Distribution of responses
Thresholds
Item | Original Scoring 0 1 2 3 4 5 |
---|---|
Burning | Re-scored 0 1 1 2 3 4 |
Tingling | Re-scored 0 1 1 2 3 4 |
Electric Shock | Re-scored 0 1 1 2 3 4 |
Temperature | Re-scored 0 1 1 2 3 4 |
Time course |
Original scoring 0 1 2 3
|
Re-scored 0 1 2 2 |
Fit to the rasch model
Individual person fit
Response dependency
Differential item function
Individual item fit
Scale and item re-appraisal
Analysis of an 7-item PD-Q outcome measure
Person-item distribution
Unidimensionality
Unidimensionality | Item location | Person location | Item fit residual | Person fit residual | Item Trait Interaction | PSI | |
---|---|---|---|---|---|---|---|
9 item PD-Q (original) |
p = 0.065 95%CI 0.048–0.082 | Z = 0.00 SD = 0.37 | Z = 0.14 SD = 0.69 | Z = 0.77 SD = 3.65** | Z = -0.28 SD = 1.26** |
χ
2 (27) = 104.8 p <0.000** | 0.77 |
7 item PD-Q |
p = 0.028 95%CI 0.011–0.045 | Z = 0.00 SD = 0.34 | Z = -0.11 SD = 0.99 | Z = 0.36 SD = 3.39** | Z = -0.39 SD = 1.20** |
χ2 (10) = 16.78, p = 0.079 | 0.79 |