An audit of pulmonary function laboratories in the West Midlands

Pulmonary function testing has become an integral part of the assessment and follow-up of patients with pulmonary disease. Many factors can influence the results produced by a laboratory. This audit was performed to examine the extent of variation in the pulmonary function test results amongst all laboratories in the West Midlands. This was followed by an attempt to determine the cause of this variation.

Phase 1. Three normal healthy subjects each underwent a set of pulmonary function tests in all 22 laboratories in the West Midlands. Information regarding technicians' qualifications, training and seniority, protocol and equipment used were obtained in the form of a questionnaire. Phase 2. All 22 laboratories were asked to calculate the predicted values on the same nine sets of demographic data. These data included both sexes, ethnic minorities and range of ages. In addition technical aspects of each laboratory were investigated including the assessment of volume and gas analysers with standard gases containing known concentrations of helium and carbon monoxide.

Phase 1. Significant variations (P < 0.05) were observed in all measured values of pulmonary function tests of the three subjects. Significant variations (P < 0.05) were also observed in all predicted values except total lung capacity. Phase 2. There were significant variations (P < 0.05) amongst laboratories in calculating the predicted values of all components of pulmonary function tests. No significant differences were observed in the measurement of volume or concentration of carbon monoxide or helium.