A new staging strategy for chronic obstructive pulmonary disease

Figures & data

Table 1 Classification criteria for GOLD and FEV₁/ht² staging from spirometry alone. FEV₁% is the FEV₁ expressed as a percentage of FVC. FEV₁PP is the FEV₁ expressed as a percentage of the subject’s predicted value

GOLD staging		FEV1/ht^2 staging
Stage	Criteria	Stage	Criteria
0	FEV1% ≥70%
1	FEV1% < 70% and
	FEV1PP ≥ 80%	1	0.5 < FEV1/ht^2
2	FEV1% < 70% and
	FEV1 PP < 80%	2	0.4 < FEV1/ht^2 ≤ 0.5
3	FEV1% < 70% and
	FEV1PP < 50%	3	0.3 < FEV1/ht^2 ≤ 0.4
4	FEV1% < 70% and
	FEV1PP < 30%	4	FEV1/ht^2 ≤ 0.3

Table 2 Descriptive data for age, height and spirometric values for the 1095 patients in the study (644 female) showing mean, standard deviation (SD) and median values

	Mean (SD)	Median
Age	61.8 (9.9)	63.0
Ht in meters	1.66 (0.09)	1.65
FVC in L	2.25 (0.76)	2.14
FVCSR	−1.87 (1.10)	−1.86
FEV1 in L	1.21 (0.45)	1.14
FEVSR	−3.21 (1.02)	−3.24
FEV1PP	46.7 (14.5)	45.5
FEV1/ht^2	0.43 (0.15)	0.41
FEV1%	54.4 (12.2)	55.0
FEV1%SR	−3.31 (1.76)	−3.23
PEF in L/s	3.60 (1.47)	3.33
PEFSR	−3.11 (1.32)	−3.28

Table 3 Univariate analysis: Indices that were found by Cox regression to be univariate predictors of survival with χ² value for strength of prediction and its significance value

Index	χ^2value	p value
FEV1/ht^2	161	<0.0001
Age	159	<0.0001
FEV1	127	<0.0001
FEV1PP	111	<0.0001
FEV1%	97	<0.0001
FEV1SR	18	<0.0001
Sex	12	<0.001
BMI	11	<0.001
Weight	8	0.004
Height	0

Table 4 Multivariate analysis: The table shows the covariate hazard ratios (HR) for death (with 95% confidence limits) for Cox proportional hazards models using sex and the quintiles of age and various methods for expressing FEV₁ impairment. The HR values are contrasts against the hazard estimated for the first stage of each group and for male contrasted with female. Chi-square values are shown for each model

		FEV1/ht^2 Chi square = 289		Raw FEV1 Chi square = 276		FEV1PP Chi square = 269		FEV1SR Chi square = 218
		HR	95% CL	HR	95% CL	HR	95% CL	HR	95% CL
Age	youngest quintile	1.0		1.0		1.0		1.0
	quintile 2	1.8	(1.3 to 2.4)	1.8	(1.3 to 2.4)	2.0	(1.5 to 2.6)	2.1	(1.6 to 2.9)
	quintile 3	2.2	(1.6 to 2.9)	2.2	(1.7 to 3.0)	2.6	(2.0 to 3.5)	3.1	(2.4 to 4.2)
	quintile 4	2.5	(1.8 to 3.3)	2.5	(1.9 to 3.3)	3.2	(2.4 to 4.3)	4.1	(3.1 to 5.4)
	oldest quintile	3.1	(2.4 to 4.1)	3.1	(2.3 to 4.1)	4.3	(3.3 to 5.7)	6.0	(4.5 to 7.9)
FEV1 index	best quintile	1.0		1.0		1.0		1.0
	quintile 2	1.6	(1.2 to 2.1)	1.6	(1.2 to 2.1)	1.5	(1.1 to 1.9)	1.2	(0.9 to 1.5)
	quintile 3	2.0	(1.5 to 2.7)	1.9	(1.4 to 2.5)	1.8	(1.4 to 2.4)	1.6	(1.3 to 2.0)
	quintile 4	2.4	(1.8 to 3.2)	2.4	(1.8 to 3.2)	2.4	(1.8 to 3.0)	2.0	(1.5 to 2.5)
	worst quintile	4.0	(3.0 to 5.2)	3.9	(3.0 to 5.1)	3.4	(2.6 to 4.3)	2.6	(2.0 to 3.3)
Male		1.5	(1.3 to 1.7)	1.8	(1.5 to 2.0)	1.1	(0.9 to 1.3)	1.1	(0.9 to 1.3)

Table 5 Cross tabulation of concordance in the 1095 subjects between GOLD classification (GOLD stages 0 to 4) and FEV₁/ht² classification for COPD severity. The table shows the number of subjects dying (nd) under follow up as a fraction of the total number N within that group (nd/N), the estimated Kaplan-Meier mean survival for that group as years in bold and the 95% confidence limits for the estimate in parenthesis. Aggregate results for each columns and row as a whole are also shown

	Staging by FEV1/ht^2
	Stage 1(>0.5)			Stage 2 (>0.4 and ≤0.5)			Stage 3 (>0.3 and ≤0.4)			Stage 4 (≤0.3)
GOLD 0	29/75	11.2	(10.2–12.2)	13/29	9.8	(8.4–11.3)	12/15	9.0	(7.1–10.8)	2/2	5.7	(0.0–13.3)	56/121	10.6	(9.8–11.4)
GOLD 2	88/195	10.8	(10.2–11.4)	66/101	9.3	(8.5–10.2)	15/18	6.2	(4.7–7.6)	–	–	–	169/314	10.1	(9.6–10.6)
GOLD 3	17/37	10.7	(9.6–11.9)	101/150	8.7	(8.0–9.4)	194/253	7.9	(7.4–8.4)	76/85	6.1	(5.2–6.9)	388/525	8.0	(7.7–8.4)
GOLD 4	1/1	–	–	–	–	–	11/13	6.6	(4.3–8.9)	98/112	5.8	(5.1–6.5)	110/126	6.0	(5.2–6.7)
	135/308	11.0	(10.5–11.4)	180/280	9.1	(8.6–9.7)	232/299	7.8	(7.4–8.3)	176/199	5.9	(5.4–6.5)

Figure 1 The mean survival for each FEV₁/ht² group and each GOLD stage with 95% confidence limit bars and the number of subjects in each column.

Figure 2 Plot of the number of subjects in each of the groups for the FEV₁/ht² staging system on the left and the GOLD staging system on the right with the mean survival of each group stated inside the relevant column.