The Neurological Impairment Scale: reliability and validity as a predictor of functional outcome in neurorehabilitation

Figures & data

Table 1. Demographics of the study populations for Parts 1 and 2.

	Part 1 – n = 428		Part 2 – n = 94
	Mean	SD	Mean	SD
Age (years)	49.5	15.3	42.9	14.5
Length of stay (days)	–	–	93	62
Mean time since onset (days)	–	–	104	71
	n	%	n	%
Males:Females	270:158	63:37	59:35	63:37
Diagnosis
Acquired brain injury	315	74%	79	84%
Vascular (stroke, SAH)	212	50%	41	44%
Traumatic	63	15%	28	30%
Other (e.g. Hypoxic/inflammatory)	40	9%	10	11%
Spinal cord injury	38	9%	7	7%
Guillain-Barré and other peripheral neuropathies	26	6%	5	5%
Multiple sclerosis	21	5%	7	–
Others	27	6%	3	3%

SAH = Sub-arachnoid Haemorrhage.

Table 2. NIS score ranges, item-total correlations and loadings on first two principal components using Varimax rotation.

	Descriptives			Rotated component matrix
	Median (IQR)	Range	Item total correlations	Factor 1 Physical	Factor 2 Cognitive
Eigen value				3.6	2.3
% variance				20.4	14.6
NIS Items
Left upper limb	0 (0–1)	0–3	0.43**	0.493
Right upper limb	1 (0–2)	0–3	0.44**	0.502
Left lower limb	1 (0–2)	0–3	0.47**	0.677
Right lower limb	1 (0–2)	0–3	0.50**	0.693
Trunk	1 (0–1)	0–2	0.50**	0.670
Tone/contractures	1 (0–2)	0–3	0.63**	0.697
Sensation	1 (0–2)	0–3	0.55**	0.629
Perception	0 (0–1)	0–3	0.38**		0.498
Speech and language	1 (0–2)	0–3	0.45**		0.580
Cognitive	1 (1–2)	0–3	0.33**		0.808
Behaviour	0 (0–0)	0–3	0.23**		0.635
Mood	1 (0–1)	0–3	0.40**		0.526
Vision	1 (0–1)	0–3	0.31**		0.562
Hearing	0 (0–0)	0–2	0.09
Pain	1 (0–1)	0–3	0.50**	0.505
Fatigue	1 (1–2)	0–3	0.52**	0.543
Other	0 (0–0)	0–2	0.12*

** significant at p < 0.001, * significant at p < 0.05.

Table 3. Inter-rater agreement: item-by-item linear-weighted kappa coefficients interpreted according to Landis and Koch [19].

	Agreement between two doctors (n = 47)			Agreement between Medical and MD Team scores (n = 94)
Item	Kappa	95% CI*	Interpretation	Kappa	95% CI	Interpretation
Left upper limb	0.94	0.72–1.0	Almost perfect	0.76	0.61–0.92	Substantial
Right upper limb	0.90	0.69–1.0	Almost perfect	0.74	0.59–0.90	Substantial
Left lower limb	0.93	0.72–1.0	Almost perfect	0.82	0.66–0.97	Almost perfect
Right lower limb	0.85	0.65–1.0	Almost perfect	0.76	0.92–0.59	Substantial
Trunk	0.87	0.64–1.0	Almost perfect	0.43	0.27–0.59	Moderate
Tone	0.63	0.44–0.82	Substantial	0.45	0.31–0.60	Moderate
Sensation	0.82	0.59–1.0	Almost perfect	0.65	0.51–0.79	Substantial
Perception	0.85	0.60–1.0	Almost perfect	0.63	0.47–0.79	Substantial
Speech	0.90	0.68–1.0	Almost perfect	0.81	0.66–0.96	Almost perfect
Cognitive	0.84	0.63–1.0	Almost perfect	0.66	0.52–0.79	Substantial
Behaviour	0.94	0.69–1.0	Almost perfect	0.13	0–0.27	Slight
Mood	0.75	0.54–0.96	Substantial	0.57	0.43–0.72	Moderate
Vision	0.80	0.56–1.0	Substantial	0.68	0.52–0.84	Substantial
Hearing	0.79	0.52–1.0	Substantial	0.77	0.59–0.95	Substantial
Pain	0.76	0.58–0.94	Substantial	0.43	0.29–0.56	Moderate
Fatigue	0.58	0.40–0.77	Moderate	0.39	0.27–0.52	Fair
Other	0.84	0.63–1.0	Almost perfect	0.44	0.29–0.59	Moderate
Total NIS Kappa	0.81	0.63–0.99	Almost perfect	0.69	0.56–0.95	Substantial
ICC	0.95	0.91–0.97		0.92	0.88–0.95

*95% Confidence intervals (CI) were calculated as +/−1.96 s standard error and the upper limit truncated at a maximum of 1.0.

Figure 1. Box and whisker plots for total NIS scores at admission and discharge. Figure 1 shows a box and whiskers plot of the total NIS scores as rated by the MD and medical teams on admission and the MD team at discharge. There was no significant difference between the two admission ratings (mean difference 0.03, 95% CI −1.16–1.11, t = 0.045, p = 0.96). However, there was a significant reduction in team-rated total scores between admission and discharge (see Table 4).

Table 4. Descriptive statistics for NIS and UK FIM + FAM scores as rated by the MD Team on admission and discharge (n = 73).

						Paired sample t tests
Admission	Mean	SD	Median	IQR	Range	t	p	ES*
Neurological Impairment Scale (NIS)
Physical Subscale	14.0	6.7	13	10–19	1–28
Cognitive Subscale	8.2	6.2	7	4–11	0–21
Total Score	22.2	11.6	19	15–28	4–48
Discharge
Physical Subscale	11.8	6.8	11	7–17	0–27
Cognitive Subscale	6.7	5.6	5	2–8	0–21
Total Score	18.3	11.5	15	10–22	3–46
Change
Physical Subscale	−2.2	2.9	−2	−4–0	−11–5	6.4	<0.001	0.73
Cognitive Subscale	−1.5	2.4	−1	−3–0	−11–3	5.3	<0.001	0.64
Total Score	−3.7	4.1	−3	−7–−1	−18–5	7.8	<0.001	0.90
UK Functional Assessment Measure (FIM + FAM)
Motor Subscale	53.9	30.0	51	21–86	16–108
Cognitive Subscale	56.3	27.0	61	32–79	14–95
Total Score	110.1	52.0	123	63–156	30–189
Discharge
Motor Subscale	74.3	33.3	87	47–102	16–111
Cognitive Subscale	69.5	24.6	77	59–88	14–98
Total Score	143.8	55.6	166	109–188	30–206
Change
Motor Subscale	20.4	16.5	17	6–33	−2–62	−10.5	<0.001	−1.26
Cognitive Subscale	13.3	11.9	11	5–18	−5–55	−9.5	<0.001	−1.14
Total Score	33.7	23.4	31	14–52	−3–93	−12.3	<0.001	−1.48

*Effect size (ES) calculated as Cohen’s d allowing for the correlation between the mean.

Table 5. Pearson correlations for admission and change scores (n = 73).

	Admission scores						Change scores
	NIS Physical	NIS Cognitive	NIS Total	FIM + FAM Motor	FIM + FAM Cognitive	FIM + FAM Total	NIS Physical	NIS Cognitive	NIS Total	FIM + FAM Motor	FIM + FAM Cognitive
Admission
NIS Physical
NIS Cognitive	0.62***
NIS Total	0.91***	0.89***
FIM + FAM Motor	−0.86***	−0.62***	−0.85***
FIM + FAM Cognitive	−0.62***	−0.90***	−0.83***	0.67***
FIM + FAM Total	−0.81***	−0.82***	−0.90***	0.92***	0.90***
Change score
NIS Physical	−0.18	0.24*	0.02	0.09	−0.17	−0.20
NIS Cognitive	−0.28*	−0.42***	−0.39**	0.27*	0.35*	0.28*	0.19
NIS Total	−0.29*	−0.07	−0.21	0.22	0.09	0.17	0.82***	0.72***
FIM + FAM Motor	−0.16	−0.45***	−0.34*	−0.06	0.36**	0.12	−0.56***	−0.02	−0.42***
FIM + FAM Cognitive	0.07	0.17	0.13	−0.22	−0.42***	−0.35**	−0.28*	−0.51***	−0.49***	0.34**
FIM + FAM Total	−0.08	−0.23*	−0.17	−0.15	0.05	−0.13	−0.54***	−0.27*	−0.54***	0.88***	0.75***

*p < 0.05, **p < 0.01, ***p < 0.001.

NIS = Neurological Impairment Scale, FIM + FAM = UK Functional Assessment Measure.

Figure 2. Box and whisker plots for change in total FIM + FAM domain scores between admission and discharge in the impairment “responder” and “non-responder” groups. Figure 2 shows box and whiskers plots of the FIM + FAM change scores, in patients who did and did not demonstrate change in the NIS score during their rehabilitation programme. Both groups improved overall, but impairment “responders” made significantly greater gains in both motor and cognitive function than the “non-responders”.

Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159–74

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