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

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

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

^a Performed with the sample divided into six class intervals according to person locations on the measured variables.
^b Nonuniform DIF was not detected.
^c Original NHP item numbers in parenthesis.
^d Analyses of variance of deviations from model expectation along the latent trait across people with PD and PAD.
^e Direction of observed DIF, PAD > PD indicates higher probability for people with PAD to endorse an item, and vice verse.
NHPD, Nottingham Health Profile index of Distress; DIF, differential item functioning; PD, Parkinson's disease; PAD, peripheral arterial disease.

ISSN: 1477-7525