Small airways obstruction syndrome in clinical practice.
OBJECTIVE
Small airways obstruction syndrome (SAOS) is a particular pulmonary function test (PFT) pattern showing decreased VC and FEV(1) but a normal FEV(1)/VC ratio and TLC. The significance of this syndrome in clinical practice has not been comprehensively investigated.


METHODS
This study retrospectively identified all patients who had performed PFT that showed a SAOS pattern at a university teaching hospital over 1 year. A simple algorithm for differential diagnosis was developed and validated.


RESULTS
Of the 3207 PFT performed, 153 (4.8%) showed a pattern indicating SAOS. Among these, a final diagnosis was confirmed for 85 (63.4%) of the patients. The causes of SAOS included both restrictive and obstructive lung diseases with the leading causes being early interstitial lung disease (n = 20; 23.3%), chest wall deformity (n = 12; 14.1%) and asthma (n = 10; 11.6%). Using a cut-off point of TLC of <95% predicted value to identify restrictive ventilatory defects (P = 0.002) and of > or =95% predicted combined with RV/TLC > or =55% to identify obstructive ventilatory defects (P < 0.001), a simplified algorithm with good accuracy (86.6%) was identified. Validation in an independent group showed accuracy of 91%.


CONCLUSIONS
The PFT pattern called SAOS is not uncommon. The most common causes of SAOS were early interstitial lung disease, chest wall deformity and asthma. A diagnostic algorithm was proposed, which may help physicians' decision-making in their daily practice.
Chen
Chiung-Zuei
CZ
Division of Chest Medicine, Department of Internal Medicine, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan.
Lin
Chien-Chung
CC
Lee
Cheng-Hung
CH
Chang
Han-Yu
HY
Hsiue
Tzuen-Ren
TR
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003937:Diagnosis, Differential; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D017563:Lung Diseases, Interstitial / Q000175:diagnosis / Q000503:physiopathology; D008173:Lung Diseases, Obstructive / Q000175:diagnosis* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D014797:Vital Capacity / Q000502:physiology