Am. J. Respir. Crit. Care Med., Vol 153, No. 4, Apr 1996, 1309-1313.
Standardization of multiple spirometers at widely separated times and places
WS Linn, JC Solomon, H Gong Jr, EL Avol, WC Navidi and JM Peters
Environmental Health Service, Rancho Los Amigos Medical Center, Downey, California, USA.
We designed a system for a multiyear longitudinal study of lung function in
12 widely separated communities, intending to minimize variation in
instrument-related data. We used multiple rolling-seal spirometer/personal
computer systems. Calibrations were checked before, during, and after each
day's field testing, using multiple calibration syringes with electronic
readouts. The syringes were rotated to obtain data for each
syringe-spirometer combination. Before and after each annual field testing
season, a laboratory reference spirometer system was calibrated against a
water-displacement device and an electronic frequency counter, and then
compared against each field spirometer and syringe. Field equipment
consistently met American Thoracic Society (ATS) specifications. Variance
among spirometers exceeded variance among syringes. A spirometer
occasionally changed its volume readout by approximately 1 to 2 %. More
rarely, a syringe changed its delivered volume by approximately 1%.
Syringes' electronic readouts tracked changes in delivered volume. Syringe
readouts were the most stable component of the system, and were more
reproducible than the laboratory water-displacement calibration. We
conclude that variation in spirometers may limit the reliability of
epidemiologic findings, even when these spirometers meet ATS
specifications. Frequent calibration checks traceable to an independent
standard, and adjustment of individual test results, can reduce measurement
error.