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Zhu-Quan Su,1,* Wei-Jie Guan,1,* Shi-Yue Li,1,* Ming Ding,2 Yu Chen,1 Mei Jiang,1 Xiao-Bo Chen,1 Chang-Hao Zhong,1 Chun-Li Tang,1 Nan-Shan Zhong1 1State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Health, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, People’s Republic of China; 2Department of Respiratory Medicine, The Affiliated Zhongda Hospital of Southeast University, Medical School of Southeast University, Nanjing, People’s Republic of China *These authors contributed equally to this work Background: Spirometry confers limited value for identifying small-airway disorders (SADs) in early-stage COPD, which can be detected with impulse oscillometry (IOS) and endobronchial optical coherence tomography (EB-OCT). Whether IOS is useful for reflecting small-airway morphological abnormalities in COPD remains unclear. Objectives: To compare the diagnostic value of spirometry and IOS for identifying SADs in heavy-smokers and COPD based on the objective assessment with EB-OCT. Methods: We recruited 59 COPD patients (stage I, n=17; stage II, n=18; stage III–IV, n=24), 26 heavy-smokers and 21 never-smokers. Assessments of clinical characteristics, spirometry, IOS and EB-OCT were performed. Receiver operation characteristic curve was employed to demonstrate the diagnostic value of IOS and spirometric parameters. Results: More advanced staging of COPD was associated with greater abnormality of IOS and spirometric parameters. Resonant frequency (Fres) and peripheral airway resistance (R5–R20) conferred greater diagnostic values than forced expiratory volume in one second (FEV1%) and maximal (mid-)expiratory flow (MMEF%) predicted in discriminating SADs in never-smokers from heavy-smokers (area under curve [AUC]: 0.771 and 0.753 vs 0.570 and 0.558, respectively), and heavy-smokers from patients with stage I COPD (AUC: 0.726 and 0.633vs 0.548 and 0.567, respectively). The combination of IOS (Fres and R5–R20) and spirometric parameters (FEV1% and MMEF% predicted) contributed to a further increase in the diagnostic value for identifying SADs in early-stage COPD. Small airway wall area percentage (Aw% 7–9), an EB-OCT parameter, correlated significantly with Fres and R5–R20 in COPD and heavy-smokers, whereas EB-OCT parameters correlated with FEV1% and MMEF% in advanced, rather than early-stage, COPD. Conclusions: IOS parameters correlated with the degree of morphologic abnormalities of small airways assessed with EB-OCT in COPD and heavy-smokers. Fres and R5–R20 might be sensitive parameters that reliably reflect SADs in heavy-smokers and early-stage COPD. Keywords: chronic obstructive pulmonary disease, optical coherence tomography, diagnostic value, impulse oscillometry, small airway disorder

PTEN hamartoma tumour syndrome is associated with germline mutations in the tumour suppressor gene, PTEN (phosphatase and tensin homolog gene), leading to formation of hamartomas due to unregulated cellular proliferation. Two patients presented with complications of hamartomas, which subsequently revealed multiple polyposis of mixed histologies throughout their gastrointestinal tracts. There was no family history for PTEN hamartoma tumour syndrome and both were eventually detected to have de novo PTEN mutations. Despite fulfilling diagnostic criteria and having high probabilities of a PTEN mutation (computed using PTEN Cleveland Clinic score), there was delayed diagnosis of PTEN hamartoma tumour syndrome due to limited awareness amongst treating clinicians. Thus PTEN hamartoma tumour syndrome should still be considered as a differential in patients with similar gastrointestinal manifestations for early diagnosis and intervention.