The Diagnostic Importance of a Reduced FEV₁/FEV₆

Figures & data

Table 1.  Database Characteristics of the 4 Groups Studied

	# of Patients	Only FEV1/FEV6 reduced	%	Only FEV1/FVC reduced	%	Both Ratios reduced	%	Both Ratios Normal	%
Total Adult Database	43,630	582		2,243		14,549		26,256
1st Time Spirometry	22,837	302		1,158		6,593		14,784
African-American	8,392	78	0.9	424	5.1	2,271	27.1	5,619	67.0
Caucasian	14,445	224	1.6	734	5.1	4,322	29.9	9,165	63.4
Female	12,965	173	1.3	579	4.5	3,450	26.6	8,763	67.6
Male	9,872	129	1.3	579	5.9	3,143	31.8	6,021	61.0
Smokers*	7,312	106	35.1	414	35.8	2,750	41.7	4,042	27.3
With Volumes	12,040	154		649		3,197		8,040
African-American	4,407	34	0.8	225	5.1	1,054	23.9	3,094	70.2
Caucasian	7,633	120	1.6	424	5.6	2,143	28.1	4,946	64.8
With DLCO	14,154	174		742		3,891		9,347
African-American	5,097	39	0.8	261	5.1	1,295	25.4	3,502	68.7
Caucasian	9,057	135	1.5	481	5.3	2,596	28.7	5,845	64.5
With Inspir Capacity	12,480	166		665		3,348		8,301
African-American	4,457	34	0.8	226	5.1	1,072	24.1	3,125	70.1
Caucasian	8.023	132	1.6	439	5.5	2,276	28.4	5,176	64.5

Ethnic and smoking distribution of groups studied.

* Smoking history obtained at time of demographic information prior to testing.

Table 2.  Mean of Variables of 4 Study Groups ± Standard Deviation

	Only FEV1/FEV6 reduced	Only FEV1/FVC reduced	Both Ratios reduced	Both Ratios Normal
# Patients	302	1,158	14,549	26,253
Expir Time (sec) ± SD	8.1 ± 1.5	14.8 ± 3.7	12.9 ± 4.1	10.0 ± 2.7
Age (yrs) ± SD	62.3 ± 16.5	62.5 ± 12.6	61 .9 ± 14.3	57.8 ± 14.7
BMI ± SD	28.7 ± 8.7	30.6 ± 6.9	28.5 ± 7.4	31.9 ± 8.1
FEV1%Pred ± SD	71.0 ± 19.2	76.3 ± 16.3	56.2 ± 19.2	86.3 ± 18.3
FVC%Pred ± SD	79.6 ± 21.4	90.3 ± 19.1	79.7 ± 20.1	87.3 ± 18.4
FEV1/FVC% ± SD	68.3 ± 3.6	64.7 ± 4.0	53.6 ± 10.9	77.0 ± 5.7
FEV6%Pred ± SD	81.3 ± 21.6	83.8 ± 18.0	72.8 ± 19.7	87.2 ± 18.3
FEV1/FEV6% ± SD	69.9 ± 3.3	72.9 ± 5.0	60.8 ± 8.8	79.9 ± 4.6
RV%Pred ± SD	1 16.4 ± 32.0	114.3 ± 30.5	145.1 ± 49.6	98.3 ± 28.9
TLC%Pred ± SD	95.3 ± 17.3	100.0 ± 16.3	106.4 ± 19.5	92.7 ± 16.7
RWTLC%Pred ± SD	122.4± 24.8	113.8 ± 22.2	134.8 ± 30.7	106.0 ± 22.0
Insp Cap%Pred ± SD	79.2 ± 25.2	92.4 ± 22.2	79.8 ± 24.8	93.3 ± 24.3
DLCO%Pred ± SD	72.1 ± 22.1	76.6 ± 18.3	65.2 ± 21 .4	78 .9 ± 18.7

This table shows the mean values analyzed in each of the 4 study groups along with their standard deviations.

Table 3.  Differences Between Mean Values Studied

	Only FEV1/FEV6 reduced minus Only FEV1/FVC reduced		Only FEV1/FEV6 reduced minus Both ratios reduced		Only FEV1/FVC reduced minus Both ratios reduced
Expir Time (s)	−6.7	p < 0.0001	−4.8	p < 0.0001	1.9	p < 0.0001
Age (yrs)	−0.2	p = 0.8489	0.4	p = 0.6060	0.6	p = 0.1778
BMI%	−2.0	p < 0.0001	0.2	p = 0.6155	2.2	p < 0.0001
FEV1%Pred	−5.2	p < 0.0001	14.8	p < 0.0001	20.1	p < 0.0001
FVC%Pred	−10.7	p < 0.0001	−0.1	p = 0.9581	10.7	p < 0.0001
FEV1/FVC%	3.6	p < 0.0001	14.7	p < 0.0001	11.1	p < 0.0001
FEV6%Pred	−2.5	p = 0.0373	8.5	p < 0.0001	17.6	p < 0.0001
FEV1/FEV6	−3.1	p < 0.0001	9.0	p < 0.0001	12.1	p < 0.0001
RV%Pred	2.2	p = 0.4276	−28.7	p < 0.0001	−30.9	p < 0.0001
TLC%Pred	−4.7	p = 0.0018	−11.1	p < 0.0001	−6.4	p < 0.0001
RWTLC%Pred	8.5	p < 0.0001	−12.5	p < 0.0001	−21.0	p < 0.0001
Insp Cap%Pred	−13.1	p < 0.0001	−0.6	p = 0.7522	12.6	p < 0.0001
DLCO%Pred	−4.5	p = 0.0050	6.9	p < 0.0001	11.4	p < 0.0001

Pair-wise comparisons of differences in mean values for the 3 groups that had reduced ratios of either the FEV₁/FEV₆ or the FEV₁/FVC or if both ratios were reduced.

Figure 1.  Expiratory Times if Only FEV₁/FEV₆ or FEV₁/FVC is Obstructed.

Table 4.  Of the 302 patients with only a reduced FEV₁FVC₆, 100 of them (below) had future repeat spirograms

	Repeat Spirometry Results
	Reduced FEV1/FVC	Normal FEV1/FVC	P
# of patients (total of 100)	60	40
1st Test ExpTime (sec)	7.9	8.2
Repeat Test Exp Time (sec)	11.4	9.2
Change (sec)	3.5	1.0	p < 0.0001

This table demonstrates when the group of patients with only a reduced FEV₁/FEV₆ ratio had a significantly longer mean expiratory time, their FEV₁/FEV₆ ratio dropped below the 95% LLN.

Table 5.  Diagnoses of subjects with only a reduced FEV₁/FEV₆ ratio (302 subjects)

	n	%
COPD	137	45.4%
Asthma	90	29.8%
Other obstructions*	8	2.7%
No obstruction, but smoked > 1 5 pk yr	36	11.9%
	Total	89.7%
Other Diagnostic Categories
Total smokers > 15 pk yr	198	65.6%
Only restriction Dx §	12	4.0%
Restriction + Obstruction†	8	2.7%

This table indicates that of the 302 subjects with only a reduced FEV₁/FEV₆ ratio, 90% had strong clinical evidence to indicate they were not false positives for airways obstruction.

* Tracheal obstruction, bronchiectasis

§ Sarcoid (5), ALS (2), effusions (3), lobectomy (2)

† Sarcoid (5), effusions (1), fibrosis (2)

Table 6.  Breakdown of patients with one or both ratios reduced.

	Both Ratios Reduce	Only FEV1/FVC Reduced	Only FEV1/FEV6 Reduced	Total With Reduced Ratios
# of Obstructed Patients	6,593	1,158	302	8,053
% of Obstructed Patients	81.90%	14.30%	3.80%	100.00%

Distribution of total pateints with obstruction based on a reduced FEV₁/FEV₆ and/or reduced FEV₁/FVC.