Pulmonary function testing: detection of invalid performance

We surveyed physician members of the American Thoracic Society and their technicians regarding indicators of the validity of PFTs. Surveys were returned by 50 physicians and 52 technicians. Both groups felt that consistency of effort and the shape/slope of the curve were important indicators, with behavioral observations rated slightly lower. Approximately 38% of physicians and 19% of technicians felt that they detected 75% or fewer of individuals giving inadequate effort during PFTs. Twenty percent of physicians and 29% of technicians were using quantitative criteria other than those recommended by the 1979 "Snowbird" technical paper to determine acceptability of PFTs. Twenty-eight percent of physicians and 31% of technicians spontaneously indicated that patients pursuing compensation or disability claims for pulmonary disorders were most likely to give suboptimal effort. Empirical research into the impact and detection of suboptimal effort on PFTs is encouraged.