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Table 4 NHPD items with uniform DIF by diagnosis (PD vs PAD) a, b

From: Cross-diagnostic validity of the Nottingham health profile index of distress (NHPD)

Item c F-value d P-value DIF direction e
4 (4) Unbearable pain 15.32361 0.000107 PAD > PD
6 (7) Feeling on edge 32.24345 0.000000 PD > PAD
7 (8) Painful to change position 23.15150 0.000004 PAD > PD
8 (9) Feel lonely 10.95699 0.001024 PD > PAD
11 (20) Losing temper easily 28.24274 0.000000 PD > PAD
17 (29) Takes long to get to sleep 26.16763 0.000000 PAD > PD
18 (30) Feel like a burden 12.83750 0.000385 PD > PAD
  1. a Performed with the sample divided into six class intervals according to person locations on the measured variables.
  2. b Nonuniform DIF was not detected.
  3. c Original NHP item numbers in parenthesis.
  4. d Analyses of variance of deviations from model expectation along the latent trait across people with PD and PAD.
  5. e Direction of observed DIF, PAD > PD indicates higher probability for people with PAD to endorse an item, and vice verse.
  6. NHPD, Nottingham Health Profile index of Distress; DIF, differential item functioning; PD, Parkinson's disease; PAD, peripheral arterial disease.