Validation of the i-BODE Index as a Predictor of hospitalization and Mortality in Patients with COPD Participating in Pulmonary Rehabilitation

Figures & data

Table 1.  Variables and point allocation used for the computation of the i-BODE index

Variable	0 points	1 point	2 points	3 points
FEV1% predicted	≥65	50–64	36–49	≤35
Distance walked on ISWT (m)	≥250	150–249	80–149	<80
MRC Dyspnea Grade	1–2	3	4	5
BMI (kg/m^2)	>21	≤21

Table 2.  Baseline characteristics of patients attending the rehabilitation program according to subsequent survival and hospitalization

	All	Hospitalized during follow-up (COPD)	Hospitalized during follow-up (all causes)	Died during follow-up
N (mean and SD unless stated)	674	421	557	325
Females,%	64.2	67.5	65.4	60.0
Age, years (SD)	69.2 (9.2)	69.2 (9.1)	69.6 (9.1)	71.4 (8.2)
Pack-years (range)	40.4 (0–150)	39.7 (0–150)	40.1 (0–150)	41.1 (0–150)
Current smoking,%	26.1	25.1	24.9	26.6
FEV1,% predicted (SD)	36.7 (13.3)	34.7 (12.0)	36.6 (13.3)	34.0 (12.6)
Prednisolone treatment,%	7.6	8.8	7.9	11.7
Long-term oxygen therapy,%	6.5	8.3	7.0	10.8
SatO2 (air),% (range)	94.3 (83–99)	94.0 (83–99)	94.2 (83–99)	93.7 (83–99)
Desaturation during SWT >4%,%	49.1	53.2	48.8	56.3
SWT, meter (mean and range)	188 (10–520)	180 (10–470)	182 (10–460)	158 (10–460)
MRC dyspnea score	3.9 (0.86)	4.0 (0.84)	3.9 (0.86)	4.0 (0.84)
BMI, kg/m^2	25.3 (5.8)	24.8 (5.6)	25.2 (5.8)	24.1 (5.4)
Admissions to hospital the previous year^1 (mean and range)	0.88 (0–14)	1.81 (0–12)	1.75 (0–14)	1.12 (0–14)
Bed days the previous year^1 (mean and range)	5.27 (0–100)	12.58 (0–100)	11.90 (0–100)	6.53 (0–100)

¹due to exacerbation in COPD; SD: standard deviation; SWT: Shuttle walking test; MRC: Medical Research Council; BMI: body mass index.

Table 3.  Predictors of all-cause mortality

	i-BODE
	points	N	Univariate	Multivariate­­­^1
ISWT	0	183	1	1
	1	221	1.59 (1.15–2.22)	1.48 (1.05–2.08)
	2	206	3.04 (2.21–4.17)	2.49 (1.78–3.48)
	3	64	3.48 (2.35–5.16)	3.07 (2.03–4.63)
		Wald:	65.6	41.8
BMI	0	497	1	1
	1	177	1.34 (1.06–1.70)	1.59 (1.23–2.04)
		Wald:	6.2	13.0
FEV1%	0	26	1	1
	1	83	0.75 (0.35–1.60)	0.97 (0.44–2.16)
	2	206	1.11 (0.56–2.19)	1.19 (0.57–2.45)
	3	359	1.26 (0.65–2.47)	1.36 (0.66–2.79)
		Wald:	7.0	3.1
MRC	0	15	1	1
	1	237	1.0 (0.44–2.28)	0.87 (0.38–2.00)
	2	222	1.29 (0.57–2.93)	1.17 (0.51–2.67)
	3	200	2.29 (1.01–5.22)	1.83 (0.79–4.21)
		Wald:	38.1	25.1
i-BODE	0–10	674	1.30 (1.22–1.38)	1.28 (1.20–1.37)
		Wald:	71.3	53.4

Adjustments: ¹Age and sex; pack-years, current smoking, oxygen saturation at rest, desaturation >4% during SWT, maintenance prednisolone, LTOT.

Figure 1.  Survival curves (Kaplan-Meier) for the four quartiles of the i-BODE index. Quartile 1 is a score of 0 to 4, quartile 2 is a score of 5, quartile 3 is score of 6 and quartile 4 is a score of 7 to 10.

Figure 2.  (a) Time to first admission for all causes (Kaplan-Meier). Log Rank = 32.5, p < 0.001. Quartile 1 is a score of 0 to 4, quartile 2 is a score of 5, quartile 3 is score of 6 and quartile 4 is a score of 7 to 10. (b) Time to first admission for COPD exacerbation (Kaplan-Meier). Log-Rank = 42.2; p < 0.001. Quartile 1 is a score of 0 to 4, quartile 2 is a score of 5, quartile 3 is score of 6 and quartile 4 is a score of 7 to 10.

Table 4.  Adjusted risk of hospitalization due to exacerbation in COPD and all causes

	i-BODE
	points	N	Due to exacerbation in COPD^1	All Causes^2
ISWT	0	183	1	1
	1	221	1.01 (0.77–1.33)	1.25 (1.00–1.57)
	2	206	1.50 (1.13–1.98)	1.71 (1.35–2.17)
	3	64	1.72 (1.16–2.55)	2.08 (1.50–2.87)
		Wald:	15.8	29.6
BMI	0	497	1	1
	1	177	1.37 (1.10–1.70)	1.21 (1.00–1.47)
		Wald:	7.8	3.8
FEV1%	0	26	1	1
	1	83	1.21 (0.58–2.53)	0.69 (0.43–1.13)
	2	206	2.06 (1.05–4.06)	0.95 (0.61–1.48)
	3	359	2.01 (1.02–3.94)	0.91 (0.59–1.41)
		Wald:	11.8	5.1
MRC	0	15	1	1
	1	237	1.20 (0.56–2.58)	1.19 (0.65–2.19)
	2	222	1.55 (0.72–3.31)	1.31 (0.71–2.40)
	3	200	2.35 (1.09–5.05)	2.02 (1.10–3.73)
		Wald:	27.5	27.6
i-BODE	0–10	674	1.21 (1.14–1.28)	1.15 (1.09–1.20)
		Wald:	38.8	32.4

Adjustments:

¹Age, sex, pack-years, oxygen saturation at rest, desaturation >4% during SWT, and LTOT.

²Age and sex.