ANALYSIS OF VARIABILITY IN INTERPRETATION OF SPIROMETRIC TESTS

The objective of this study was to quantify the degree of disagreement in interpretation of spirometries and in the definition of the airway obstruction and response to bronchodilators (Ed) in different publica tions. Two surveys were carried out in which two groups of 15 pulmonol ogists were asked to identify in several spirometries the presence and degree of obstructive or restrictive defects (OD or RD), the response to Ed and whether the test was assessable or not. Three 'problem' spi rograms (PS) were included. For RD there was 76.1% of maximum agreemen t (MA). For OD the MA was 63.6%. Of the PS only 14% of the tests with a higher than 40% variation among the curves, 14% of those which did n ot include the graphic records and 33% of those with a considerably im perfect curve were considered nonassessable. The degree of disagreemen t for response to Ed was 24% (this implies 53.3% of possible maximal d isagreement). Besides, every original article whose title or summary r eferred to 'asthma', 'chronic obstructive lung disease' or 'chronic ai rflow obstruction' which was published from July 1991 to July 1993 in two respiratory medical journals (Chest and Thorax) was examined. Elev en different criteria to define obstruction were found. The most frequ ently used was FEV1/FVC <70% (33.3%). Five different definitions of a positive response to Ed were found. The most popular was an increase i n FEV1 > 15% of the initial value (76%). We conclude that there is ver y often disagreement in the interpretation of conventional spirometry. The definition of obstruction and reversibility in clinical trials is not uniform and great care must be taken when extrapolating the resul ts from one publication to another since the composition of its sample s could be substantially different.