Evaluación de diferentes valores de referencia espirométricos para el diagnóstico de alteración restrictiva en población chilena

Abstract

In 1988, the Chilean Respiratory Society decided to get national spirometric reference values (SRV), because those used at that time (Knudson et al) underestimated the values in our population. Since then, and using national SRV, it has been observed an increase of the positive false restrictive impairment diagnoses. Our aim was to analyse the probability of making a restrictive impairment diagnosis, according to different spirometric reference values, using the total lung capacity (TLC) measurement as a gold standard. Patients and Methods: We analysed the spirometries from male and female patients older than 59 y.o., in whom lung volumes by helium dilution, had been measured concurrently in our laboratory during 2004. Restrictive impairment was substantiated (confirmed) if TLC was lower than its theoretical value (European Community) minus 1,64· RSD (standard deviation of the residual). Spirometries from the same patients were analysed with different SRV and several statistical indicators of diagnostic tests were calculated. Results: 91 patients (mean age: 72 y.o. ranging from 60 to 89) were assessed. We confirmed a restrictive impairment in 35 of them (38%). Using national SRV, sensitivity (S) was 86%, specificity (E) 59% and the post-test probability (PPT) 57%. Using NHANES III SRV, S was 54%, E was 91% and PPT 79% Using Knudson SRV S was 49%, E 93% and PPT 81%, while by using Platino study SRV, S was of 49%, E was 77% and PPT 57%. Conclusion: Similarly to previous reports, we have found an important difference in the probability of diagnosing restriction in our population, according to the SRV used