[Error factors in spirometry].
Spirometry is the more frequently used method to estimate pulmonary function in the clinical laboratory. It is important to comply with technical requisites to approximate the real values sought as well as adequate interpretation of results. Recommendations are made to establish: 1--quality control 2--define abnormality 3--classify the change from normal and its degree 4--define reversibility. In relation to quality control several criteria are pointed out such as end of the test, back-extrapolation and extrapolated volume in order to delineate most common errors. Daily calibration is advised. Inspection of graphical records of the test is mandatory. The limitations to the common use of 80% of predicted values to establish abnormality is stressed. The reasons for employing 95% confidence limits are detailed. It is important to select the reference values equation (in view of the differences in predicted values). It is advisable to validate the selection with local population normal values. In relation to the definition of the defect as restrictive or obstructive, the limitations of vital capacity (VC) to establish restriction, when obstruction is also present, are defined. Also the limitations of maximal mid-expiratory flow 25-75 (FMF 25-75) as an isolated marker of obstruction. Finally the qualities of forced expiratory volume in 1 sec (VEF1) and the difficulties with other indicators (CVF, FMF 25-75, VEF1/CVF) to estimate reversibility after bronchodilators are evaluated. The value of different methods used to define reversibility (% of change in initial value, absolute change or % of predicted), is commented. Clinical spirometric studies in order to be valuable should be performed with the same technical rigour as any other more complex studies.
Quadrelli
S A
SA
Instituto de Investigaciones Médicas Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Montiel
G C
GC
Roncoroni
A J
AJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001993:Bronchodilator Agents / Q000494:pharmacology; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D005540:Forced Expiratory Flow Rates / Q000187:drug effects; D005541:Forced Expiratory Volume / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D013147:Spirometry / Q000592:standards*; D014797:Vital Capacity / Q000187:drug effects
D001993:Bronchodilator Agents
Análisis de los factores de error en la espirometría.