COMPARISON OF TWO METHODS IN THE DIAGNOSIS OF AIRWAY

OBSTRUCTION

İlknur Başyiğit, Serap Barış, Haşim Boyacı, Füsun Yıldız

Kocaeli University Faculty of Medicine Chest Disease Department

INTRODUCTION

Pulmonary function test has been used for the diagnosis and follow up the treatment of airway diseases.

Different definitions of airway obstruction cause major changes of prevalence estimates.

-Viegi G, Pedreschi M, Pistelli F et al. Prevalence of airway obstruction in a general population. European Respiratory Society vs American Thoracic Society definition. Chest 2000; 117:Suppl.2, 339S-345S.-Shirtcliffe P, Weatherall M, Marsh S, Travers J, Hansell A, McNaughton A, Aldington S, Muellerova H, Beasley R. COPD prevalence in a random population survey: a matter of definition. Eur Respir J

2007; 30:232-239.

INTRODUCTION

It is suggested that the fixed ratio for FEV1/FVC which is recommended in 2001 GOLD report for practical reasons and it is also accepted by ATS/ERS, would overestimate the prevalence of COPD in older population since FEV1/FVC will decrease with age and underestimate the frequency of obstructive disorders in younger population.

-Hardie JA, Buist AS, Vollmer WM, Ellingsen I, Bakke PS, Murkve O. Risk of overdiagnosis of COPD in asymptomatic elderly never-smokers. Eur Respir J 2002;20: 1117-1122.-Hnizdo E, Glindmeyer HW, Petsonk EL, Enrigt P, Buist AS. Case definitions for chronic obstructive pulmonary disease. COPD 2006;3: 95-100.-Roberts SD,Farber MO, Knox KS, Phillips GS, Bhatt NY, Mastronarde JG, et al. FEV1/FVC ratio of %70 misclasifies patients with obstruction at the extremes of age. Chest 2006; 130:200-236.

INTRODUCTION

In 2005; ATS/ERS suggested to use Lower Limit of Normal (LLN; level lower than 5% predicted) for definition of airway obstruction instead of fixed ratio and this suggestion was supported by several recent studies.

-Roberts SD, Farber MO, Knox KS et al. FEV1/FVC ratio of 70% misclassifies patients with obstruction at extremes of age. Chest 2006;130: 200-206.-Hansen JE, Sun XG, Wasserman K. Spirometric criteria for airway obstruction. Use percentage of FEV1/FVC ratio below the fifth percantile, Not <70%. Chest 2007;131:349-355.

INTRODUCTION

Use of fixed ratio for definition of airway obstruction was recommended again in 2006 GOLD report, until longitudinal studies investigating validity of LLN performed.

AIM

The aim of this study was to compare the LLN and fixed ratio for the FEV1/FVC level in the diagnosis of airway obstruction.

MATERIAL AND METHOD

A questionnaire for respiratory symptoms was applied and physical examination was performed in the teachers.

Pulmonary function test (PFT) was done by a technician using portable spirometer in cases that accept to join the study and can perform the spirometry maneuver.

PFT was performed using Koko Legend portable spirometer.

MATERIAL AND METHOD

Mean age, gender, respiratory symptoms and physical examination of participants were recorded.

FEV1, FVC, FEV1/FVC values were determined.

LLN for the FEV1/FVC ratio was determined as the 5% lower of the predicted FEV1/FVC levels and calculated for each case.

RESULTS

Totally 616 cases included in the study, 55% of the cases were male (n: 338), 45% of them were female (n: 278) and mean age was 38.9 ± 8.8 years.

Mean FEV1 level was 3.3 ± 0.7 l and mean FVC level was 4.1 ± 0.9 l.

TABLE-1: DEMOGRAPHIC CHARACTERISTICS

n: 616 Male: 338 (%55)Female: 278 (%45)

Mean age 38.9 ± 8.8 years (min:18, max:63)

<40 years, n(%) 344 (%56)

≥40 years, n(%) 272 (%44)

FEV1 mean (L) 3.3 ± 0.7

FVC mean (L) 4.1 ± 0.9

RESULTS

FEV1/FVC was lower than 70% in 4 cases while the ratio was found to be LLN in 12 of the cases.

All of 4 cases who determined as obstructive

by fixed FEV1/FVC ratio were also defined as obstructive according to LLN.

TABLE-2:THE NUMBER OF OBSTRUCTIVE AND NON-OBSTRUCTIVE CASES ACCORDING TO LLN AND FEV1/FVC

LLN

Obstructive Non-obstructive

Total

FEV1 / FVC

Obstructive 4 0 4

Non-obstructive

8 604 612

Total 12 604 616

TABLE-3:DISTRUBITION OF OBSTRUCTIVE AND NON-OBSTRUCTIVE CASES ACCORDING TO AGE

OBSTRUCTIVE NON-OBSTRUCTIVE

FEV1/FVC LLN FEV1/FVC LLN

<40 years 0 6 344 338

≥40 years 4 6 268 266

RESULTS

Five of the 8 cases who determined as obstructive by using the LLN for the FEV1/FVC ratio, had complain of dyspnea,

Three of the 8 cases reported the episodes of dyspnea and wheezing

Two of them had doctor-diagnosed asthma. Prolongation of expiration and diffuse

expiratory rhonchi was found in the physical examination of the 4 cases.

CONCLUSION

It is suggested that using LLN for FEV1/FVC ratio might be more accurate than fixed cut-off in the diagnosis of airway obstruction especially in the younger population.