Reference ranges and determinant factors for exhaled nitric oxide in a healthy korean elderly population.
OBJECTIVE
Exhaled nitric oxide (NO) is a useful non-invasive biomarker for asthma diagnosis; however, the literature suggests that exhaled NO levels may be affected by demographic factors. The present analysis investigated determinant factors that present exhaled NO reference levels for Korean elderly adults.


METHODS
For reference levels, we analyzed the baseline data of healthy adult participants in the Ansung cohort. The fraction of exhaled NO (FeNO) was measured by NIOX MINO®. The characterization of the subjects was performed through structured questionnaires, spirometry, and methacholine challenge tests. To validate the diagnostic utility of the determined reference levels, asthma patients were recruited from medical institutions for FeNO measurement.


RESULTS
A total of 570 healthy subjects were analyzed (mean age, 59.9±12.3; male, 37.0%) for reference levels. FeNO levels significantly correlated with weight, height, body mass index, atopy, or forced expiratory volume in 1 second % predicted by simple linear regression analysis. Multiple linear regression analysis identified gender as an independent determinant for FeNO levels; subsequently, the reference values for FeNO were 18.2±10.6 ppb (5th to 95th percentile, 6.0 to 37.4 ppb) for males and 12.1±6.9 ppb (5th to 95th percentile, 2.5 to 27.0 ppb) for females. The diagnostic utility of FeNO reference levels was validated by receiver operating curve analysis (area under curve, 0.900 for males and 0.885 for females) for diagnosing asthma. The optimal cutoff values for the prediction of asthma were 30.5 ppb for males and 20.5 ppb for females.


CONCLUSIONS
The current analysis presented reference ranges and the diagnostic utility of FeNO levels for asthma in Korean elderly adults.
Department of Internal Medicine, Pusan National University School of Medicine, Busan, Korea.
Eun-Jung
EJ
Jo
Department of Internal Medicine, Pusan National University School of Medicine, Busan, Korea. ; Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea. ; Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea.
Woo-Jung
WJ
Song
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea. ; Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea.
Tae-Wan
TW
Kim
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea. ; Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea.
Heung-Woo
HW
Park
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea. ; Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea. ; Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
Yoon-Seok
0000-0003-3157-0447
YS
Chang
Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
Tae-Bum
TB
Kim
Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Korea.
Sang-Heon
SH
Kim
Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
Gyu-Young
GY
Hur
Department of Internal Medicine, Eulji University College of Medicine, Seoul, Korea.
Jae-Hyung
JH
Lee
Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Korea.
Ho-Joo
HJ
Yoon
Department of Internal Medicine, Ajou University College of Medicine, Suwon, Korea.
Hae-Sim
0000-0003-2614-0303
HS
Park
Department of Preventive Medicine, Ajou University School of Medicine, Suwon, Korea.
Nam-Ho
NH
Cho
Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
Hee-Bom
HB
Moon
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea. ; Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea.
Kyung-Up
KU
Min
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea. ; Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea.
Sang-Heon
SH
Cho
Adult; asthma; nitric oxide; reference values