Table 2

Reduced NHP38 version obtained through Classical Test Theory (CTT): the NHP20

Original NHP38 items By dimension
1st set of criteria for reduction: Discrimination (r) & Endorsement (p)
2nd set of criteria for reduction: Factor analysis*
NHP20

Dimension
No. items
α
Items deleted as r < 0.40
Items deleted as P < 0.20
Items deleted as communality <0.30
Items deleted as main loading <0.40
Items deleted as difference between similar loadings ≤ 0.1
No. Items remaining

Energy (EN)
3
.76
-
-
-
-
EN2, EN3
1
Pain (P)
8
.90
-
P2
-
-
P4, P5
5
Emotional Reactions (EM)
9
.82
EM8
-
EM5, EM7
-
-
6
Sleep (SL)
5
.81
SL1
-
-
-
-
4
Social Isolation (SO)
5
.78
-
SO2, SO3 SO4, SO5
SO1
-
-
0
Physical Mobility (PM)
8
.83
-
PM1, PM3 PM8
-
-
PM6
4
Summary Index
38
.95
(28 items remaining, α = 0.94)




20 (α = .92)

* Principal Axis Extraction (4 factors) and Promax rotation (Factor intercorrelation range: 0.50 – 0.73) NHP items are: EN1-I'm tired all the time; EN2-Everything is an effort; EN3-I soon run out of energy; P1-I have pain at night; P2-I have unbearable pain; P3-I find it painful to change position; P4-I'm in pain when I walk; P5-I'm in pain when I'm standing; P6-I'm in constant pain; P7-I'm in pain when going up/down stairs; P8-I'm in pain when I'm sitting; EM1-Things are getting me down; EM2-I've forgotten to enjoy myself; EM3-I'm feeling on edge; EM4-These days seem to drag; EM5-I lose my temper easily these days; EM6-I feel as if I'm losing control; EM7-Worry is keeping me awake at night; EM8-I feel that life is not worth living; EM9-I wake up feeling depressed; SL1-I take tablets to help me sleep; SL2-I'm waking in the early hours ...; SL3-I lie awake for most of the night; SL4-It takes me long time to get to sleep; SL5-I sleep badly at night; SO1-I feel lonely; SO2-I'm finding it hard to contact people; SO3-I feel there is nobody I am close to; SO4-I feel I am a burden to people; SO5 I'm finding hard to get on with people;PM1-I can only walk about indoors; PM2-I find it hard to bend; PM3-I'm unable to walk at all; PM4-I have trouble getting up/down stairs; PM5-I find it hard to reach for things; PM6-I find it hard to dress myself; PM7-I find it hard to stand for long; PM8-I need help to walk about outside.

Prieto et al. Health and Quality of Life Outcomes 2003 1:27   doi:10.1186/1477-7525-1-27