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Comparison between specified percentage and fifth percentile criteria for spirometry interpretation in Thai patients
Author(s) -
DEJSOMRITRUTAI WANCHAI,
WONGSURAKIAT PHUNSUP,
CHIERAKUL NITIPATANA,
CHAROENRATANAKUL SUCHAI,
NANA ARTH,
MARANETRA KHUN NANTA
Publication year - 2002
Publication title -
respirology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 85
eISSN - 1440-1843
pISSN - 1323-7799
DOI - 10.1046/j.1440-1843.2002.00379.x
Subject(s) - medicine , spirometry , percentile , vital capacity , population , kappa , cardiology , asthma , lung function , mathematics , statistics , diffusing capacity , lung , environmental health , geometry
Objectives: The present study was conducted to determine the degree of agreement between the interpretation of spirometry using a specified percentage of predicted value (SPC) and the fifth percentile (FPC) as the cut off between normal and abnormal. Methodology: Spirometric values were collected for 1754 subjects attending the respiratory service at Siriraj Hospital between February 2000 and April 2001. These values included forced vital capacity (FVC), forced expiratory volume in 1 s (FEV 1 ), FEV 1 /FVC, maximal mid‐expiratory flow (FEF 25–75% ) and peak expiratory flow (PEF). A comparison of results between SPC and FPC was performed. The SPC cut‐off values for FVC, FEV 1 , FEV 1 /FVC, FEF 25‐75% and PEF were 80% predicted, 80% predicted, 70%, 65% predicted and 80% predicted, respectively. The FPC cut‐off values were calculated from reference equations for the Thai population. Inter‐rater agreement was calculated as the kappa score. Results: High kappa scores were obtained for FVC (0.84), FEV 1 (0.88) and FEF 25–75% (0.80). However, poor agreement was found for FEV 1 /FVC (0.72) and PEF (0.61). When the cut‐off values for SPC were modified to 90% of predicted values for FEV 1 /FVC and to 65% of predicted values for PEF, agreement was substantially improved to 0.92 and 0.89, respectively. Conclusions: Interpretation by SPC using cut‐off values of 80% predicted for FVC and FEV 1 and 65% predicted for FEF 25–75% resulted in good agreement with FPC. However, the SPC cut‐off values for FEV 1 /FVC and PEF should be modified to 90% predicted and 65% predicted, respectively.