Relevant and Redundant Lung Function Parameters in Discriminating Asthma from COPD

Figures & data

Table 1 Demography of subjects in this study

Sex	Disease		Age	FEV1	FEV1 over VC	VCmax	TLCO	VA	TLC	RV
Male	Asthma	Mean	46.7	87.3	89.5	97.6	91.0	94.0	101.9	111.9
		Sd	15.5	18.6	14.3	16.0	19.1	14.1	12.8	35.0
	COPD	Mean	63.7	66.7	75.8	88.2	59.0	87.4	104.8	134.0
		Sd	12.0	19.0	15.9	17.2	20.6	15.7	17.8	40.4
Female	Asthma	mean	42.3	90.1	95.0	103.2	76.4	93.2	103.7	111.8
		Sd	16.9	17.7	13.6	14.7	13.7	12.0	12.0	25.7
	COPD	Mean	58.8	69.6	79.2	96.9	52.4	89.1	109.9	141.2
		Sd	11.8	17.4	14.5	17.9	18.1	14.6	16.8	37.9

The lung function data were expressed as percent of the predicted value [[2]].

Table 2 Individual areas under the ROC curve for the most relevant parameters listed in Table 3

	AUC ROC	sd
TLco	0.8328	0.4226
VA	0.6169	0.5747
Post-bronchodilator MEF25	0.8262	0.4226
Post-bronchodilator VC	0.6337	0.5679
Post-bronchodilator PEF	0.7141	0.5229
Pre-bronchodilator MEF50	0.8443	0.4047
Pre-bronchodilator MEF25	0.8443	0.4092

Table 3 The presence of lung function parameters in the four selection methods as significant asthma-COPD discriminators in 500 bootstrapped logistic regression analyses

Forward selection	%	Backward selection	%	Stepwise selection	%	Best score	%
method	presence	method	presence	method	presence	method	presence
TLCO	100.0	TLCO	100.0	TLCO	100.0	TLCO	100.0
VA	70.8	VA	83.6	VA	69.4	Pre-bd MEF25	78.0
Post-bd MEF50	46.2	Post-bd VC	82.2	Post-bd MEF50	42.6	Pre-bd MEF50	73.2
Post-bd VC	41.8	Post-bd MEF50	65.8	Post-bd VC	41.2	VA	69.0
Post-bd PEF	36.8	Pre-bd PEF	51.8	Post-bd PEF	32.8	Post-bd MEF50	67.8
TLCbb	34.6	pre-bd VC	45.2	Pre-bd PEF	29.8	Pre-bd PEF	55.4
Pre-bd PEF	31.0	R0.5	35.4	Post-bd FEV1	27.8	Post-bd VC	54.2
Post-bd FEV1	30.8	Rinex	34.2	Post-bd MEF50	27.0	Post-bd MEF25	43.4
Post-bd MEF25	30.0	Post-bd FVC	33.8	TLCbb	25.2	Pre-bd FVC	40.4
Rinex	24.4	Post-bd FEV1	33.0	Rinex	21.4	Post-bd FVC	34.2

The presence is reported as the percentage a parameter appeared as a significant discriminator. (post-bd stands for post-bronchodilation, pre-db stands for pre-bronchodilation).

Table A. 1 Calculation examples: two patients

	Units	A Measured	B = Ln(A) Ln(measured)	C Regression factor	D = B*C Result
Female diagnosed with asthma
TLCO	mmol/min/kPa	7.8	2.0541	3.56	7.313
Alveolar volume	L	4.9	1.5892	−5.87	−9.329
MEF50 post-dilator	L/sec	6.8	1.9169	2.02	3.872
VCmax post-dilator	L	4.2	1.4351	5.00	7.176
PEF post-dilator	L/sec	10.17	2.3191	−2.56	−5.937
Intercept				1.29	1.29
Sum of all terms (= t)					4.385
Predicted probability for asthma = (exp(t)/(1 + exp(t)))					0.988
Male diagnosed with COPD
TLCO	mmol/min/kPa	4.4	1.4816	5.45	8.075
Alveolar volume	L	6.6	1.8871	−8.14	−15.361
MEF50 post-dilator	L/sec	0.8	−0.2201	0.64	−0.141
VCmax post-dilator	L	4.4	1.4816	2.87	4.252
PEF post-dilator	L/sec	5.18	1.6448	1.31	8.520
Intercept				−1.23	−1.23
Sum of all terms (= t)					−2.250
Predicted probability for asthma = (exp(t)/(1 + exp(t)))					0.095

Quanjer Ph H, Tammeling G J, Cotes J E, Pedersen O F, Peslin R, Yernault J-C. Lung volumes and forced expiratory flows. Eur Respir J 1993; 6: 5–40, [CSA]

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