Hand-held turbine spirometer: agreement with the conventional spirometer at baseline and after exercise

Portable hand-held spirometers are widely used in outpatient clinics and in field surveys when examining children for asthma. However, the validity of the results obtained from the hand-held spirometers has not been assessed in population-based studies. We evaluated the agreement between the forced expiratory volume (FEV1) values got by the conventional flow volume spirometer (FVS) and the pocket-sized turbine spirometer (TS) at baseline and after exercise, among the 212 children screened for asthma and asthma-like symptoms from a population of 1633 school-aged children. The comparison was made between and within three diagnostic groups: clinical asthma (n = 34), possible asthma (n = 31), and controls (n = 147). In general, the differences in FEV1 between the FVS and the TS were small. For all children, the mean difference in FEV1 and the limits of agreement (difference +/-2 s.d.) was 0.05 l (0.23 to -0.13) at baseline and 0.06 l (0.24 to -0.12) after exercise. No significant differences were observed in the agreement between the diagnostic groups. In conclusion, although FEV1 results obtained by the hand-held spirometer are not interchangeable with those by the conventional spirometer, they are in reasonable agreement. The agreement is similar both at baseline and after exercise, and is not influenced by the presence of asthma.