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Abstract

Background

Although the postbronchodilator FEV₁/FVC is the gold standard for diagnosing COPD, it is not easily obtainable due to various reasons. This study aims to investigate whether FEV₁/FEV₆ may serve as an easily accessible surrogate for FEV₁/FVC in detecting airway obstruction and COPD.

Methods

Eligible articles were screened from PubMed, Web of Science and Scopus. The Quality Assessment of Diagnostic Accuracy Studies-2 was applied for quality assessment. The pooled sensitivity, specificity, and area under the curve (AUC) of the summary receiver operating curve were calculated to evaluate the diagnostic performance of FEV₁/FEV₆ in detecting airway obstruction and COPD and to determine the optimal cutoff value. Sensitivity analyses, subgroup analyses and meta-regression were performed to explore the source of heterogeneity.

Results

With 28 eligible articles and 65,744 subjects, the FEV₁/FEV₆ ratio showed good diagnostic performance in detecting both airway obstruction (sensitivity: 0.87, specificity: 0.94, AUC 0.95) and COPD (sensitivity: 0.83, specificity: 0.88, AUC 0.91). Further analyses of the optimal cutoff value suggested that an FEV₁/FEV₆<0.72 was the best criterion for detecting airway obstruction (sensitivity: 0.84, specificity: 0.97, AUC 0.96), whereas an FEV₁/FEV₆<0.74 was the best criterion for detecting COPD (sensitivity: 0.87, specificity: 0.89, AUC 0.93). The results of subgroup analyses and meta-regression suggested that study design and geographical location may affect the heterogeneity of both sensitivity and specificity in detecting airway obstruction and COPD.

Conclusion

The FEV₁/FEV₆ may serve as an easily accessible alternative in detecting airway obstruction and COPD. However, application of FEV₁/FEV₆ may also be constrained by availability and affordability of devices. Further studies are required to determine the best-suited population for FEV₁/FEV₆ application.

Keywords

airway obstruction chronic obstructive pulmonary disease spirometry meta-analysis

1. Introduction

Chronic obstructive pulmonary disease (COPD) is a heterogeneous lung condition characterized by non-fully reversible airflow obstruction and multiple respiratory symptoms, with a prevalence of 10.3% globally and 8.6% in China.^1–3 COPD patients, especially those in low- and middle-income countries, are reported to have unmet needs for diagnostic approaches, such as low availability of standard spirometry and insufficient screening tools.⁴ A national cross-sectional study suggested that only 2.6% of COPD patients were aware of their condition in China.⁵ Further studies reported an underdiagnosis rate of over 70% in patients with COPD.^6,7 As most of the COPD patients were of mild or moderate stage of the disease, underdiagnosis at the population level still exists due to subtle or absent symptoms of patients.⁵ Implementing pre-symptomatic screening for airflow limitation and COPD may help address this gap.

Spirometry examination focusing on forced expiratory volume in 1 second (FEV₁)/forced vital capacity (FVC) is regarded as the gold standard for identifying airway obstruction (FEV₁/FVC <0.7) and COPD (FEV₁/FVC <0.7 post-bronchodilation).¹ However, application of spirometry also faces certain challenges. Since United States Preventive Services Task Force did not recommend routine COPD screening for the general asymptomatic population, there is a need for convenient tests to identify individuals with high risk of COPD.⁸ Moreover, meeting quality control for FVC was relatively difficult, especially for older adults with greater risks of airway obstruction, which also calls for a metric less reliant on FVC to identify potential airway obstruction effectively.^9,10

Forced expiratory volume in 6 seconds (FEV₆) has been regarded as a potential alternative for FVC to address the current challenges of spirometry.¹¹ FEV₆ has been shown to offer the following strengths: (1) With the widespread application of portable spirometry, measuring FEV₆ via portable devices became possible, which may improve the convenience of this examination compared to traditional spirometry.¹²; (2) FEV₆ have been shown to exhibit good diagnostic performance. A meta-analysis in 2009 revealed that the FEV₁/FEV₆ is a valid alternative for the detection of airway obstruction compared with the FEV₁/FVC.¹³ However, there are also concerns over the efficacy of FEV₁/FEV₆, especially for patients with mild airway obstruction.¹⁴ Moreover, the previous meta-analysis did not summarize the performance of FEV₁/FEV₆ in COPD. Therefore, as studies accumulated in the past 15 years, we conducted this meta-analysis to update the diagnostic accuracy of FEV₁/FEV₆ in detecting airway obstruction and COPD. Additionally, as the optimal cutoff value of FEV₁/FEV₆ remains unclear in previous meta-analysis, we also explored the best cutoff value for FEV₁/FEV₆ in detecting airway obstruction and COPD. The optimal cutoff value may be useful in the further standardization of FEV₁/FEV₆ in clinical practice.

2. Methods

This systematic review and meta-analysis was registered on the INPLASY website (INPLASY202470029) and performed following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines.¹⁵

2.1. Literature search

A literature search was conducted by two investigators independently in PubMed, Web of Science and Scopus from the inception of the databases to May 2024, and updated in December 2024 and December 2025, respectively. The details of the search strategies are presented in Table S1. References of related systematic reviews were also screened and selected to prevent omissions.

2.2. Inclusion and exclusion criteria

The inclusion criteria of this study were as follows: (1) Diagnostic tests reporting true positive (TP), true negative (TN), false positive (FP) and false negative (FN) results of FEV₁/FEV₆ in detecting airway obstruction compared with conventional spirometry. (2) Studies with a sample size of over 100. (3) Spirometry examination was performed for participants as the gold standard. Airway obstruction was defined as FEV₁/FVC<0.7 or FEV₁/FVC<lower limit of normal (LLN), regardless of bronchodilator usage; whereas COPD was defined as postbronchodilator FEV₁/FVC<0.7 or FEV₁/FVC<LLN. This study applied no restrictions regarding participants’ mean age or population source, with eligibility extended to both general and clinical populations. The exclusion criteria were as follows: (1) Duplicated data from the same database or institution, for which we included only the study with the largest population.¹⁶ (2) Studies not published in English. (3) Review, meta-analysis, editorials, research letters, abstracts and comments. (4) Data from unpublished studies. Two authors independently screened all records and any disagreement was resolved by group discussion.

2.3. Data extraction and quality assessments

Two authors independently extracted and collected data from each study, and any disagreements were resolved by group discussion. Data extraction mainly focused on the baseline characteristics of eligible studies and the diagnostic performance of FEV₁/FEV₆. The baseline characteristics included the name of the first author, publication year, continent, number of centers, study direction (prospective or not), proportion of smokers, number of cases and controls, and diagnostic criteria for airway obstruction or COPD. Diagnostic performance included every cutoff value of FEV₁/FEV₆ along with their diagnostic performance.

To evaluate the quality of eligible diagnostic tests, the Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 was applied, which evaluated the risk of bias via four aspects (patient selection, index test, reference standard and flow and timing) and assessed applicability concerns via three aspects (patient selection, index test and reference standard).¹⁷ The Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) was applied to evaluate certainty of evidence (GRADEpro).¹⁸

2.4. Statistical analysis

A meta-analysis of diagnostic accuracy was performed following the suggested guidelines.¹⁹ The sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR) and diagnostic odds ratio (DOR) were calculated. Summary receiver operating characteristic (sROC) curve analysis was also performed to evaluate the overall diagnostic performance of FEV₁/FEV₆. We first performed a pooled analysis to identify the overall diagnostic performance of FEV₁/FEV₆ in identifying airway obstruction and COPD. If the diagnostic performance of more than one cutoff value was reported in the same study, the cutoff value with the best diagnostic performance reported in the study was selected for overall analysis. Then, we summarized studies reporting the diagnostic performance of the same cutoff values from FEV₁/FEV₆<0.70 to FEV₁/FEV₆<0.80 and conducted pooled analysis for every cutoff value reported by more than three studies, which may help to identify the best cutoff value of FEV₁/FEV₆ in identifying airway obstruction and COPD. The heterogeneity of the results was assessed via the I² statistic and the Q test. A random-effect model was applied if significant heterogeneity was observed (I²>50% or p<0.05); otherwise, a fixed-effect model was applied. Sensitivity analyses were applied to evaluate the stability of results and identify potential outliers. Subgroup analyses and meta-regression were applied to evaluate the potential source of heterogeneity in categorial and continuous variables, respectively. In the subgroup analyses, we investigated whether study sample size, study design, study center, reference standard and geographical location were source of heterogeneity. In the meta-regression, we investigated whether age, smoking, sex, body mass index and spirometry results were source of heterogeneity. Deek’s funnel test was conducted to detect potential publication bias. All the statistical analyses were performed via Stata (Version 16.0) software, and a p value of <0.05 was considered to indicate statistical significance.

2.5. Patient and public involvement statement

Patients and public were not involved.

3. Results

3.1. Study screening and quality assessment

As shown in Figure 1, 2,599 records were identified during the literature search. After removing duplicate results and irrelevant records, 70 articles were selected for full-text screening, and 28 articles with 65,744 subjects (19,244 patients with airway obstruction and 46,500 without) were ultimately identified as eligible.^20–47 The baseline characteristics of these eligible articles are shown in Table 1 andTable S2. Results of the quality assessment are shown in Figure S1, suggesting that all studies were of moderate to high quality. Moreover, the patient selection and index test of some studies may introduce risk of bias to study results. All eligible articles were shown to be of moderate to high quality. GRADE score suggested that certainty of evidence was moderate for FEV₁/FEV₆ in detecting airway obstruction, and low for detecting COPD (Figure S2-3).

Figure 1.

Flow chart of study selection.

Table 1.

Baseline characteristics of studies included in this meta-analysis.

Author	Location	Number of centers	Study type	Smoking (%)	Model of spirometer for FEV₆	Diagnostic criteria of AO/COPD	The best cut-off of FEV6 reported
Lo 2025²⁰	Asia	Single-center	Cross-sectional	100.00%	COPD-6	Post-BD FEV₁/FVC<70%	0.76
Hernandez-Mezquita 2025²¹	Europe	Multi-center	Cross-sectional	100.00%	COPD-6, PiKo-6	Post-BD FEV₁/FVC<70%	0.75
Alotaibi 2023²²	Oceania	Multi-center	Cross-sectional	99.40%	COPD-6	Post-BD FEV₁/FVC<70%	0.70
Hwang 2021²³	Asia	Multi-center	Cross-sectional	100.00%	COPD-6	Post-BD FEV₁/FVC<70%	0.73
Chen 2021²⁴	Asia	Multi-center	Cross-sectional	43.10%	Handheld Expiratory Flowmeter	Post-BD FEV₁/FVC<70%	0.77
Llordés 2017²⁵	Europe	Single-center	Cross-sectional	100.00%	COPD-6	Post-BD FEV₁/FVC<70%	0.78
Ching 2017²⁶	Asia	Single-center	Cross-sectional	98.30%	COPD-6	Post-BD FEV₁/FVC<70%	0.75
Wang 2016²⁷	Asia	Multi-center	Cross-sectional	31.40%	Portable spirometer	FEV₁/FVC < 70%	0.72
Represas-Represas 2016²⁸	Europe	Multi-center	Prospective	100.00%	COPD-6	Post-BD FEV₁/FVC<70%	0.78
Labor 2016²⁹	Europe	Multi-center	Prospective	100.00%	COPD-6	Post-BD FEV₁/FVC<70%	0.78
Kim 2016³⁰	Asia	Single-center	Prospective	100.00%	COPD-6	Post-BD FEV₁/FVC<70%	0.77
Chung 2016³¹	Asia	Multi-center	Cross-sectional	Not mentioned	A Vmax 2130 Dry Rolling-seal Spirometer	FEV₁/FVC < 70%	0.75
Vam den Bemt 2014³²	Europe	Single-center	Cross-sectional	100.00%	PiKo-6	Post-BD FEV₁/FVC<70%	0.73
Bhatt 2014³³	North America	Multi-center	Retrospective	100.00%	Not applicable	Post-BD FEV₁/FVC<70%	0.73
Aghili 2013³⁴	Asia	Single-center	Cross-sectional	Not mentioned	Via-sys Health, Master Scope version 4.6	FEV₁/FVC < 70%	0.73
Thorn 2012³⁵	Europe	Multi-center	Cross-sectional	100.00%	COPD-6	Post-BD FEV₁/FVC<70%	0.73
Kishi 2011³⁶	Asia	Single-center	Cross-sectional	32.40%	A CHESTAC25 part II EX instrument	FEV₁/FVC < 70%	0.72
Frith 2011³⁷	Oceania	Multi-center	Prospective	100.00%	PiKo-6	Post-BD FEV₁/FVC<70%	0.75
Toda 2009³⁸	Asia	Multi-center	Cross-sectional	Not mentioned	FEV₆ meter	FEV₁/FVC<70%	0.75
Rosa 2007³⁹	South America	Multi-center	Cross-sectional	33.10%	An ultrasound spirometer	Post-BD FEV₁/FVC<70%	0.75
Lamprecht 2007⁴⁰	Oceania	Single-center	Cross-sectional	52.70%	The ndd EasyOne diagnostic spirometer	Post-BD FEV₁/FVC<LLN	LLN
Vandevoorde 2006⁴¹	Europe	Single-center	Cross-sectional	Not mentioned	A mass-flow sensor	FEV₁/FVC<70%	0.73
Melbye 2006⁴²	Europe	Single-center	Cross-sectional	66.60%	Sensormedics Vmax 20′	FEV₁/FVC<70%	0.73
Jensen 2006⁴³	North America	Multi-center	Cross-sectional	Not mentioned	A water-sealed spirometer connected to a linear potentiometer	FEV₁/FVC<LLN	LLN
Hansen 2006⁴⁴	North America	Multi-center	Cross-sectional	100.00%	Not applicable	FEV₁/FVC<LLN	LLN
Akpinar-Elci 2006⁴⁵	North America	Multi-center	Cross-sectional	57.40%	Automated Ohio 827 dry rolling-seal spirometers	FEV₁/FVC<LLN	LLN
Demir 2005⁴⁶	Asia	Single-center	Cross-sectional	Not mentioned	SensorMedics Vmax22 spirometer	FEV₁/FVC<70%	0.70
Swanney 2000⁴⁷	Oceania	Single-center	Cross-sectional	Not mentioned	SensorMedics model 2130 dry rolling seal spirometers	FEV₁/FVC<LLN	LLN

AO: airway obstruction; COPD: chronic obstructive pulmonary disease; FEV6: forced expiratory volume in 6 seconds; FEV1: forced expiratory volume in 1 second; FVC: forced vital capacity; Post-BD: post-bronchodilator.

3.2. Overall diagnostic performance of FEV₁/FEV₆

Among the 28 eligible articles reporting FEV₁/FEV₆ in airway obstruction, the sensitivity ranged from 0.71--0.97, and the specificity ranged from 0.67--1.00. The pooled sensitivity and specificity of the FEV₁/FEV₆ ratio reached 0.87 (95% CI 0.83, 0.90; I²=96.92%, p<0.01) and 0.94 (95% CI 0.90, 0.97; I²=98.49%, p<0.01), respectively (Figure 2(a) and Figure S4). The sROC curve suggested that the area under the curve (AUC) reached 0.95 (95% CI 0.92, 0.96) (Figure 2(A)). The PLR, NLR and DOR reached 15.6 (95% CI 8.9, 27.2), 0.14 (95% CI 0.11, 0.18) and 113.0 (95% CI 56.0, 227.0), respectively.

Figure 2.

Diagnostic accuracy of FEV₁/FEV₆ in detecting airway obstruction and COPD. (a): sROC curve of EFV1/FEV6 in detecting airway obstruction; (b): sROC curve of FEV₁/FEV₆ in detecting COPD. COPD: chronic obstructive pulmonary disease; sROC: summary receiver operating characteristic.

Sixteen articles reported the performance of FEV₁/FEV₆ in detecting COPD,^{20–26,28–30,32,33,35,37,39,40} with a sensitivity range of 0.71--0.93 and a specificity range of 0.67--0.99. The pooled sensitivity and specificity reached 0.83 (95% CI 0.79, 0.87; I²=97.10%, p<0.01) and 0.88 (95% CI 0.81, 0.93; I²=98.26%, p<0.01), respectively (Figure 2(B) and Figure S5). The sROC curve showed an AUC of 0.91 (95% CI 0.88, 0.93) (Figure 2(b)). The PLR, NLR, and DOR were 6.9 (95% CI 4.4, 10.9), 0.19 (95% CI 0.15, 0.25), and 36.0 (95% CI 20.0, 64.0), respectively.

3.3. Optimal cutoff value of FEV₁/FEV₆

The diagnostic performance of FEV₁/FEV₆ in detecting airway obstruction and COPD were presented in Tables 2 and 3 and Figure S6-22. Increasing sensitivity and decreasing specificity were observed with increasing cutoff values. An FEV₁/FEV₆<0.72 was shown to be the best cutoff value for detecting airway obstruction, with the highest sum of sensitivity (0.84, 95% CI 0.72, 0.91) and specificity (0.97, 95% CI 0.92, 0.99), as well as the highest AUC value (0.96, 95% CI 0.94, 0.98). Moreover, an FEV₁/FEV₆<0.74 was shown to serve as the best cutoff value for COPD detection, with the highest sum of sensitivity (0.87, 95% CI 0.77, 0.93) and specificity (0.89, 95% CI 0.71, 0.97), as well as the highest AUC value (0.93, 95% CI 0.91, 0.95).

Table 2.

Diagnostic accuracy of FEV₁/FEV₆ using different cut-off values in detecting airway obstruction.

Cut-off value	Number of studies	Sensitivity (95%CI)	Specificity (95%CI)	PLR (95%CI)	NLR (95%CI)	DOR (95%CI)	AUC (95%CI)
0.70	13	0.64 (0.53, 0.73)	1.00 (0.95, 1.00)	149.80 (12.70, 1761.20)	0.37 (0.27, 0.49)	410.00 (34.00, 4958.00)	0.84 (0.80, 0.87)
0.71	5	0.71 (0.59 0.80)	0.98 (0.80, 1.00)	35.00 (3.00, 402.50)	0.30 (0.21, 0.43)	117.00 (10.00, 1417.00)	0.84 (0.80, 1.00)
0.72	8	0.84 (0.72, 0.91)	0.97 (0.92, 0.99)	30.00 (10.60, 85.00)	0.17 (0.09, 0.30)	178.00 (46.00, 689.00)	0.96 (0.94, 0.98)
0.73	13	0.86 (0.80, 0.90)	0.94 (0.87, 0.97)	13.90 (6.50, 29.70)	0.15 (0.10, 0.21)	92.00 (38.00, 224.00)	0.94 (0.92, 0.96)
0.74	9	0.90 (0.79, 0.95)	0.89 (0.78, 0.95)	8.10 (3.90, 16.80)	0.12 (0.05, 0.25)	70.00 (23.00, 216.00)	0.95 (0.93, 0.97)
0.75	12	0.88 (0.81, 0.93)	0.85 (0.75, 0.91)	5.80 (3.40, 9.90)	0.14 (0.08, 0.22)	42.00 (19.00, 93.00)	0.93 (0.91, 0.95)
0.76	6	0.87 (0.75, 0.94)	0.87 (0.81, 0.91)	6.60 (4.20, 10.40)	0.15 (0.07, 0.31)	45.00 (15.00, 137.00)	0.93 (0.90, 0.95)
0.77	8	0.83 (0.76, 0.88)	0.81 (0.73, 0.87)	4.30 (3.00, 6.10)	0.22 (0.15, 0.31)	20.00 (11.00, 36.00)	0.89 (0.86, 0.91)
0.78	6	0.88 (0.82, 0.92)	0.79 (0.70, 0.86)	4.20 (3.00, 6.10)	0.15 (0.10, 0.23)	28.00 (16.00, 49.00)	0.91 (0.88, 0.93)
0.79	4	0.91 (0.84, 0.95)	0.73 (0.63, 0.82)	3.40 (2.40, 5.00)	0.12 (0.06, 0.23)	28.00 (12.00, 70.00)	0.90 (0.87, 0.92)
0.80	7	0.91 (0.86, 0.95)	0.61 (0.50, 0.71)	2.30 (1.80, 2.90)	0.14 (0.10, 0.20)	16.00 (12.00, 22.00)	0.87 (0.84, 0.90)

NLR: Negative likelihood ratio; PLR: Positive likelihood ratio; DOR: diagnostic odds ratio.

The best cutoff value was presented in BOLD.

Table 3.

Diagnostic accuracy of FEV₁/FEV₆ using different cut-off values in detecting COPD.

Cut-off value	Number of studies	Sensitivity (95%CI)	Specificity (95%CI)	PLR (95%CI)	NLR (95%CI)	DOR (95%CI)	AUC (95%CI)
0.70	10	0.60 (0.49, 0.70)	0.97 (0.89, 0.99)	19.40 (5.80, 64.90)	0.41 (0.32, 0.54)	47.00 (14.00, 153.00)	0.82 (0.78, 0.85)
0.71	5	0.71 (0.59 0.80)	0.98 (0.80, 1.00)	35.00 (3.00, 402.50)	0.30 (0.21, 0.43)	117.00 (10.00, 1417.00)	0.84 (0.80, 1.00)
0.72	5	0.75 (0.63, 0.84)	0.96 (0.84, 0.99)	18.70 (4.20, 83.30)	0.26 (0.17, 0.39)	73.00 (14.00, 377.00)	0.89 (0.86, 0.91)
0.73	9	0.84 (0.77, 0.89)	0.90 (0.79, 0.96)	8.50 (3.70, 19.40)	0.18 (0.13, 0.26)	47.00 (18.00, 123.00)	0.91 (0.89, 0.94)
0.74	6	0.87 (0.77, 0.93)	0.89 (0.71, 0.97)	8.20 (2.80, 23.70)	0.15 (0.08, 0.25)	57.00 (18.00, 174.00)	0.93 (0.91, 0.95)
0.75	10	0.86 (0.77, 0.92)	0.83 (0.70, 0.91)	5.10 (2.80, 9.00)	0.17 (0.10, 0.28)	30.00 (13.00, 68.00)	0.91 (0.89, 0.94)
0.76	5	0.82 (0.76, 0.86)	0.86 (0.79, 0.91)	5.80 (3.60, 9.40)	0.21 (0.15, 0.30)	27.00 (12.00, 60.00)	0.90 (0.87, 0.92)
0.77	8	0.83 (0.76, 0.88)	0.81 (0.73, 0.87)	4.30 (3.00, 6.10)	0.22 (0.15, 0.31)	20.00 (11.00, 36.00)	0.89 (0.86, 0.91)
0.78	6	0.88 (0.82, 0.92)	0.79 (0.70, 0.86)	4.20 (3.00, 6.10)	0.15 (0.10, 0.23)	28.00 (16.00, 49.00)	0.91 (0.88, 0.93)
0.79	4	0.91 (0.84, 0.95)	0.73 (0.63, 0.82)	3.40 (2.40, 5.00)	0.12 (0.06, 0.23)	28.00 (12.00, 70.00)	0.90 (0.87, 0.92)
0.80	7	0.91 (0.86, 0.95)	0.61 (0.50, 0.71)	2.30 (1.80, 2.90)	0.14 (0.10, 0.20)	16.00 (12.00, 22.00)	0.87 (0.84, 0.90)

NLR: Negative likelihood ratio; PLR: Positive likelihood ratio; DOR: diagnostic odds ratio.

The best cutoff value was presented in BOLD.

3.4. Sensitivity analyses, subgroup analyses and meta-regression

Sensitivity and specificity of FEV₁/FEV₆ in detecting COPD has been shown to remain stable after leave-one-out analyses (Table S3-4). The results of the subgroup analyses and meta-regression for the categorical variables were shown in Table 4. Study design, reference standard and geographical location were significant factors affecting the heterogeneity of both sensitivity and specificity in detecting airway obstruction (all p<0.01), whereas study design and geographical location were significant factors affecting the heterogeneity of both sensitivity and specificity in detecting COPD (all p<0.05). Moreover, all categorical variables significantly affected the heterogeneity of pooled sensitivity in detecting both airway obstruction and COPD. The results of the meta-regression for continuous variables were shown in Table 5. Smoking (%) may affect the heterogeneity of specificity in detecting both airway obstruction (p=0.005) and COPD (p=0.040), and FEV₁% was shown to affect the heterogeneity of specificity (p=0.029) in detecting COPD.

Table 4.

Subgroup analysis and meta-regression of categorial variables.

Parameter	Subgroup	Number of studies	Sensitivity (95% CI)	p1 (meta-regression)	Specificity (95% CI)	p2 (meta-regression)
AO
Sample size	>1000	11	0.88 (0.83, 0.92)	<0.01	0.98 (0.96, 0.99)	0.61
Sample size	<1000	17	0.87 (0.83, 0.91)		0.89 (0.83, 0.95)
Study design	Prospective	5	0.78 (0.67, 0.89)	<0.01	0.80 (0.60, 0.99)	<0.01
Study design	Retrospective	23	0.88 (0.85, 0.91)		0.96 (0.94, 0.98)
Study center	Single-center	12	0.89 (0.85, 0.93)	<0.01	0.96 (0.92, 0.99)	0.17
Study center	Multi-center	16	0.85 (0.81, 0.90)		0.93 (0.89, 0.98)
Reference standard	FEV₁/FVC<LLN	5	0.86 (0.78, 0.93)	<0.01	0.98 (0.96, 1.00)	<0.01
Reference standard	FEV₁/FVC<0.7	23	0.87 (0.84, 0.91)		0.93 (0.89, 0.97)
Geographical location	Europe	8	0.87 (0.81, 0.93)	<0.01	0.88 (0.77, 0.98)	<0.01
Geographical location	Non-Europe	20	0.87 (0.83, 0.91)		0.96 (0.94, 0.98)
COPD
Sample size	>1000	3	0.81 (0.72, 0.91)	<0.01	0.97 (0.94, 1.00)	0.87
Sample size	<1000	13	0.83 (0.79, 0.88)		0.83 (0.78, 0.90)
Study design	Prospective	5	0.78 (0.70, 0.87)	<0.01	0.80 (0.66, 0.93)	<0.01
Study design	Retrospective	11	0.85 (0.80, 0.89)		0.91 (0.86, 0.96)
Study center	Single-center	6	0.84 (0.77, 0.90)	<0.01	0.86 (0.76, 0.96)	0.20
Study center	Multi-center	10	0.82 (0.77, 0.87)		0.89 (0.82, 0.95)
Reference standard (post-bronchodilation)	FEV₁/FVC<LLN	1	0.73 (0.53, 0.93)	0.74	0.99 (0.97, 1.00)	<0.01
Reference standard (post-bronchodilation)	FEV₁/FVC<0.7	15	0.83 (0.80, 0.87)		0.86 (0.81, 0.91)
Geographical location	Europe	6	0.84 (0.78, 0.90)	<0.01	0.83 (0.71, 0.94)	0.01
Geographical location	Non-Europe	10	0.83 (0.77, 0.87)		0.90 (0.85, 0.96)

Significant results were shown in BOLD. AO: airway obstruction; COPD: chronic obstructive pulmonary disease; FEV₁: forced expiratory volume in 1 second; FVC: forced vital capacity; LLN: lower limit of normal.

Summary: Study design, reference standard and geographical location significantly affected the heterogeneity of FEV₁/FEV₆ for AO in terms of sensitivity and specificity. Study design and geographical location significantly affected the heterogeneity of FEV₁/FEV₆ for COPD in terms of sensitivity and specificity.

Table 5.

Meta-regression of continuous variables.

Parameter	Coefficient	Standard error	T	95% CI	P-value
Airway obstruction
Age
Sensitivity	0.001	0.003	0.43	-0.004, 0.007	0.673
Specificity	-0.005	0.004	-1.14	-0.013, 0.004	0.270
Smoking (%)
Sensitivity	-0.086	0.069	-1.26	-0.230, 0.057	0.223
Specificity	-0.222	0.071	-3.14	-0.370, -0.074	0.005
Male (%)
Sensitivity	-0.099	0.157	-0.63	-0.428, 0.230	0.538
Specificity	-0.294	0.154	-1.91	-0.617, 0.029	0.072
BMI
Sensitivity	-0.015	0.015	-1.02	-0.050, 0.019	0.339
Specificity	-0.014	0.020	-0.68	-0.061, 0.033	0.515
FEV₁%
Sensitivity	-0.002	0.003	-0.80	-0.008, 0.004	0.449
Specificity	-0.006	0.005	-1.13	-0.017, 0.006	0.290
FEV₁/FVC (%)
Sensitivity	-0.001	0.004	-0.21	-0.010, 0.009	0.841
Specificity	0.006	0.005	1.13	-0.006, 0.018	0.284
COPD
Age
Sensitivity	0.001	0.005	0.13	-0.011, 0.013	0.898
Specificity	-0.003	0.008	-0.39	-0.020, 0.014	0.704
Smoking (%)
Sensitivity	0.081	0.088	0.92	-0.108, 0.270	0.270
Specificity	-0.224	0.099	-2.26	-0.436, -0.012	0.040
Male (%)
Sensitivity	0.140	0.201	0.70	-0.308, 0.588	0.502
Specificity	-0.226	0.219	-1.03	-0.714, 0.262	0.327
BMI
Sensitivity	0.006	0.021	0.30	-0.046, 0.059	0.777
Specificity	0.017	0.030	0.56	-0.057, 0.091	0.594
FEV₁%
Sensitivity	-0.007	0.002	-3.03	-0.014, -0.001	0.029
Specificity	-0.00	0.004	-2.54	-0.019, 0.000	0.052
FEV₁/FVC (%)
Sensitivity	-0.006	0.004	-1.43	-0.017, 0.004	0.196
Specificity	0.003	0.006	0.43	-0.012, 0.017	0.677

COPD: chronic obstructive pulmonary disease; BMI: body mass index; FEV₁: forced expiratory volume in 1 second; FVC: forced vital capacity.

Summary: Smoking rate affected the heterogeneity of airway obstruction and COPD in terms of specificity, and FEV1% affected the heterogeneity of COPD in terms of sensitivity.

3.5. Publication bias

The results of Deek’s funnel plot asymmetry tests were shown in Figures S23-24. Although no publication bias was observed in studies for airway obstruction (p=0.10), significant publication bias was observed in studies for COPD (p<0.01).

4. Discussion

With a total of 28 article sources, this systematic review and meta-analysis suggested that the FEV₁/FEV₆, achieved by a simple handheld device, has good diagnostic performance in detecting both airway obstruction and COPD with different optimal cutoff value. Compared with FEV₁/FVC, FEV₁/FEV₆ was more easily-available for general population, and more technically acceptable for patients with severe COPD, which may serve as a more available surrogate in primary screening.

Selecting an appropriate cutoff value for FEV₁/FEV₆ is also important for optimizing its diagnostic performance. Conventional spirometry examination uses an FEV₁/FVC<0.7 as the gold standard for airway obstruction.⁴⁸ As the value of FEV₆ was lower than that of FVC, the cutoff value should be increased to reach a similar diagnostic performance to the gold standard. Currently, multiple cutoff values have been used in studies on FEV₁/FEV₆, each with its own advantages and disadvantages. However, the optimal cutoff value of FEV₁/FEV₆ requires further investigation. The results of this meta-analysis suggested that an FEV₁/FEV₆<0.72 reached the best diagnostic performance in detecting airway obstruction, whereas an FEV₁/FEV₆<0.74 reached the best performance in detecting COPD. The possible reasons for the different optimal cutoff values may be that patients with bronchodilator-confirmed COPD were associated with larger proportion of expiratory volumes after the first 6 seconds, the effects of which should be adjusted by a larger cutoff value. For some participants with airway obstruction, their obstruction may be mild and reversible, which was less affected by this effect. Moreover, according to the standardization guideline of spirometry, expiration should continue until an expiratory plateau is reached, or if not achievable, should be reproducible and maintained for at least 15 seconds.^21,49 In patients with severe airway obstruction, expiration often continues for 15 seconds. Compared with FEV₆, the expiratory volume from the 9 more seconds was large enough to affect the diagnosis of airway obstruction, suggesting that performance of FEV₁/FEV₆ may also depend on the severity of diseases.^21,49

Additionally, although the FEV₁/FEV₆ ratio has good diagnostic performance in detecting airway obstruction and COPD, the significant heterogeneity of these results cannot be ignored. The results of subgroup analyses and meta-regression suggested that study design (prospective or retrospective) and geographical location (European and non-European) were sources of heterogeneity affecting both sensitivity and specificity. As retrospective studies may increase the risk of potential bias while the number of prospective studies is relatively small, more prospective studies are needed to verify the results.⁵⁰ For studies conducted in different geographical locations, factors such as different races, clinician proficiencies and types of equipment may contribute to heterogeneous results.⁵¹ FEV₁% was also a potential source of heterogeneity according to the results of the meta-regression, which may imply that the severity of COPD may also affect the diagnostic performance of FEV₁/FEV₆. Moreover, the studies included were published from 2000--2025 and were performed with diverse clinician proficiencies, which may also serve as a potential reason for significant heterogeneity.⁵²

COPD screening approaches primarily target high-risk populations, particularly current/former smokers and individuals with occupational exposures. For potential approaches for COPD screening, the diagnostic performance of COPD screening questionnaires has also been reported in many studies. A meta-analysis reported that the COPD screening tool questionnaire reached a sensitivity of 0.66 and a specificity of 0.86 in detecting COPD patients in the general population.⁵³ A study in a Chinese population suggested that the Lung Function Questionnaire, with an AUC value of 0.785, was superior to five other COPD screening questionnaires in the Chinese population.⁵⁴ These studies suggested that despite being simple and easily accessible, these questionnaires were not sufficient to identify potential COPD patients accurately. Therefore, further studies should focus on a combination of screening questionnaires and portable spirometry to maximize diagnostic accuracy. A comparative study suggested that a combination of a COPD screening questionnaire and peak flow meter screening may become the optimal screening tool for COPD.⁵⁵ A further simulation modeling study revealed that the application of both portable spirometry and COPD screening questionnaires was cost effective and beneficial for improving population health outcomes.⁵⁶ Compared with previous studies, this meta-analysis suggested that FEV₁/FEV₆, also achieved by portable spirometry, can also be considered an alternative to portable spirometry in primary care settings, thereby reducing the burden of COPD in the long term. If the initial screening yields positive results, patients will be referred for standard pulmonary function tests to verify COPD presence. However, although the above approaches may identify patients suspicious of COPD in their early stage, they are also restricted by multiple factors including suboptimal efficacy and quality control.

This study has the following strengths. With a relatively large number of eligible studies and rigorous investigations of the optimal cutoff value, results of this meta-analysis became more robust. The application of sensitivity analyses, subgroup analyses and meta-regression were also helpful for investigation of heterogeneity. The limitations of this meta-analysis should also be discussed. (1) Significant heterogeneity was observed in our results, which can be only partly explained by subgroup analyses and meta-regression. (2) Publication bias was observed in studies reporting the diagnostic performance of FEV₁/FEV₆ in detecting COPD. These limitations may increase the risk of potential bias and affect the reliability of the study results. (3) Application of portable devices of FEV₁/FEV₆ may still be constrained by issues of accessibility and affordability, and diagnostic performance of FEV₁/FEV₆ necessitates further evaluation in future studies. (4) Only studies in English were enrolled in this meta-analysis, which may increase the risk of missing relevant non-English studies. (5) Although eligible studies were of moderate to high quality in this meta-analysis, some studies still have concerns over the aspects of patient selection and index test, which may increase the risk of bias. (6) Lastly, portable screeners for FEV₁/FEV₆ does not replace spirometry as you are unable to measure the quality of the patient effort and flow curves. Conventional spirometry for FEV₁/FVC is still the cornerstone of COPD diagnosis.

There are also some issues that worth further investigations. First of all, the performance of FEV₁/FEV₆ in specific groups of population, such as African, Hispanics or people in the high-risk occupations, was still unknown. Moreover, whether FEV₁/FEV₆ exhibit similar performance among patients with varying degrees of respiratory symptoms remained inadequately understood. Additionally, can we improve the performance of FEV₁/FEV₆ by combining it with other self-reported screening questionnaire? Further studies of FEV₁/FEV₆ are still needed to address this issue.

5. Conclusion

The FEV₁/FEV₆ may serve as an easily achieved surrogate for detecting airway obstruction and COPD, with the best cutoff values of 0.72 and 0.74, respectively. The above findings have provided additional evidence of the robustness of FEV₁/FEV₆ as a valuable indicator of respiratory health, which may become a strong addition to be applied in the primary care settings. However, application of FEV₁/FEV₆ was still constrained by multiple factors, and its diagnostic performance warranted further evaluation.

Supplemental material

Supplemental Material - Diagnostic performance of FEV₁/FEV₆ in detecting airway obstruction and chronic obstructive pulmonary disease: A systematic review and meta-analysis

Supplemental Material for Diagnostic performance of FEV₁/FEV₆ in detecting airway obstruction and chronic obstructive pulmonary disease: A systematic review and meta-analysis by Dongru Du, Sike He, Jiangyue Qin, Hao Wang, Lijuan Gao, Mei Chen, Xiaohua Li, Zhenni Chen, Fengming Luo, Yongchun Shen in Chronic Respiratory Disease.

Supplemental material

Supplemental Material - Diagnostic performance of FEV₁/FEV₆ in detecting airway obstruction and chronic obstructive pulmonary disease: A systematic review and meta-analysis

Footnotes

Acknowledgements

In 2009, Dr. Huahao Shen and his colleagues published a meta-analysis to summarize the diagnostic value of FEV₁/FEV₆ in detecting airway obstruction. This is an updated meta-analysis based on Dr Shen’s achievement, and is also a memory for Dr. Huahao Shen, who passed away on April 2024.

ORCID iDs

Jiangyue Qin

Yongchun Shen

Consent for publication

All authors have reviewed the current version of this manuscript and agreed for publication.

Author’s contributions

DD, SH and JQ: Conceptualization, Methodology, Software, Formal analysis and Writing - original draft. HW and LJ: Data curation and Software. MC, XL and ZC: Methodology and Software. FL and YS: Conceptualization, Funding acquisition, Resources, Supervision and Writing - review & editing. DD, SH and JQ contributed equally to this work. YS is the guarantor of this work.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the National Natural Science Foundation of China (W2511097, 82170046, 82470062, and 82300050) and the Sichuan Key Research and Development Program (2024NSFSC1522 and 2024YFFK0279). These funding agencies were not involved in designing the study, collecting or analyzing the data, writing the manuscript, or making decisions related to publication.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data Availability Statement

All data in this work were available from the corresponding authors with reasonable request.*

Supplemental material

Supplemental material for this article is available online.

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Supplementary Material

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Diagnostic performance of FEV 1 /FEV 6 in detecting airway obstruction and chronic obstructive pulmonary disease: A systematic review and meta-analysis

Abstract

Background

Methods

Results

Conclusion

Keywords

1. Introduction

2. Methods

2.1. Literature search

2.2. Inclusion and exclusion criteria

2.3. Data extraction and quality assessments

2.4. Statistical analysis

2.5. Patient and public involvement statement

3. Results

3.1. Study screening and quality assessment

3.2. Overall diagnostic performance of FEV1/FEV6

3.3. Optimal cutoff value of FEV1/FEV6

3.4. Sensitivity analyses, subgroup analyses and meta-regression

3.5. Publication bias

4. Discussion

5. Conclusion

Supplemental material

Supplemental Material - Diagnostic performance of FEV1/FEV6 in detecting airway obstruction and chronic obstructive pulmonary disease: A systematic review and meta-analysis

Supplemental material

Supplemental Material - Diagnostic performance of FEV1/FEV6 in detecting airway obstruction and chronic obstructive pulmonary disease: A systematic review and meta-analysis

Footnotes

Acknowledgements

ORCID iDs

Consent for publication

Author’s contributions

Funding

Declaration of conflicting interests

Data Availability Statement

Supplemental material

References

Supplementary Material

3.2. Overall diagnostic performance of FEV₁/FEV₆

3.3. Optimal cutoff value of FEV₁/FEV₆

Supplemental Material - Diagnostic performance of FEV₁/FEV₆ in detecting airway obstruction and chronic obstructive pulmonary disease: A systematic review and meta-analysis

Supplemental Material - Diagnostic performance of FEV₁/FEV₆ in detecting airway obstruction and chronic obstructive pulmonary disease: A systematic review and meta-analysis