Effect of the Changing the Lower Limits of Normal and the Interpretative Strategies for Lung Function Tests

Seung Won Ra, Ji Seon Oh, Sang-Bum Hong, Tae Sun Shim, Chae-Man Lim, Youn Suck Koh, Sang Do Lee, Woo Sung Kim, Dong-Soon Kim, Won Dong Kim, Yeon-Mok Oh
2006 Tuberculosis and Respiratory Diseases  
To interpret lung function tests, it is necessary to determine the lower limits of normal (LLN) and to derive a consensus on the interpretative algorithm. '0.7 of LLN for the FEV1/FVC' was suggested by the COPD International Guideline (GOLD) for defining obstructive disease. A consensus on a new interpretative algorithm was recently achieved by ATS/ERS in 2005. We evaluated the accuracy of '0.7 of LLN for the FEV1/FVC' for diagnosing obstructive diseases, and we also determined the effect of
more » ... ed the effect of the new algorithm on diagnosing ventilatory defects. Methods : We obtained the age, gender, height, weight, FEV1, FVC, and FEV1/FVC from 7362 subjects who underwent spirometry in 2005 at the Asan Medical Center, Korea. For diagnosing obstructive diseases, the accuracy of '0.7 of LLN for the FEV1/FVC' was evaluated in reference to the 5 th percentile of the LLN. By applying the new algorithm, we determined how many more subjects should have lung volumes testing performed. Evaluation of 1611 patients who had lung volumes testing performed as well as spirometry during the period showed how many more subjects were diagnosed with obstructive diseases according to the new algorithm. Results: 1) The sensitivity of '0.7 of LLN for the FEV1/FVC' for diagnosing obstructive diseases increased according to age, but the specificity was decreased according to age; the positive predictive value decreased, but the negative predictive value increased. 2) By applying the new algorithm, 34.5% (2540/7362) more subjects should have lung volumes testing performed. 3) By applying the new algorithm, 13% (205/1611) more subjects were diagnosed with obstructive diseases; these subjects corresponded to 30% (205/681) of the subjects who had been diagnosed with restrictive diseases by the old interpretative algorithm. Conclusion: The sensitivity and specificity of '0.7 of LLN for the FEV1/FVC' for diagnosing obstructive diseases changes according to age. By applying the new interpretative algorithm, it was shown that more subjects should have lung volumes testing performed, and there was a higher probability of being diagnosed with obstructive diseases (Tuberc Respir Dis 2006; 61: 129-136) 서 론 폐활량 측정법으로 대표되는 폐기능검사는 호흡기 환자의 폐기능을 정확히 평가하고 호흡기 질환의 진 단과 중등도 판정, 그리고 경과 관찰 및 치료를 판정 하는데 사용하는 중요한 검사이다 1 . 폐기능검사를 해 석하는 데 필수적인 사항으로 첫째 정상예측식(reference equation) 선정, 둘째 정상하한치(lower limits of normal) 선정, 셋째 해석흐름도 합의 등이다. 첫째, 정상예측식은 인종과 나라마다 차이가 나며 정상예측식이 바뀌면 폐기능검사 해석에 유의하게 차 이가 생기므로 정상예측식 선정에 주의해야 한다 2 . 둘째, 정상하한치를 선정하는 방법은 세 가지가 있 는데 '고정값 방법', '95% 신뢰구간 방법', '95백분위수 (percentile) 방법'등이다. 예를 들면 만성폐쇄성폐질
doi:10.4046/trd.2006.61.2.129 fatcat:2ksrquud6benxmjczxgbfuv63m