Jack” and “Jill” have devised a quality assurance procedure during which they alternate each month testing themselves on the PFT machine at “Hilltop Medical Center.” During the second week of December, Jill was surprised that her DLCO, which was usually 22 to 27 units (mL/min/mm Hg), was now 17 to 18. Jack had just left for the holidays, and he usually maintained the instrument, so Jill waited until he returned in the first week of January to test himself.
Jack’s DLCO was usually 39 to 41 units but was now reduced to 32 to 34. He looked at the absorbent columns on the PFT equipment and discovered that both were half blue. Jill sheepishly admitted that she had mistakenly put carbon dioxide absorbent granules (soda lime) in both columns during the week of the Thanksgiving holiday. He replaced the second absorber with Drierite and tested himself again; his results were back to his usual 39 to 40 units. Oops! Jack and Jill had tumbled down. About 30 patients had been tested since Thanksgiving, including several with interstitial lung disease enrolled in “Doctor Porsche’s” clinical trial.
PFT instrument errors like this unfortunately occur too commonly, even with expensive new models. Such errors result in misclassification of PFT interpretations that can have serious consequences for patients. For example, DLCO results are used to decide who gets on waiting lists for lung volume reduction surgery for patients with severe COPD, and lung transplant lists for patients with idiopathic pulmonary fibrosis. A 20% error can easily make a clinically important difference for a patient.
The American Thoracic Society and the European Respiratory Society published updated PFT guidelines in 2005 that recommend weekly biologic control tests for all DLCO machines, yet only half of PFT laboratories in a recent survey in the United States performed even monthly bioQC testing (like Jack and Jill). This means that all patients tested within a given month could have errors in their DLCO results before a problem was detected and rectified, as in this case. The introduction of a good bioQC program allows each laboratory to establish its known variability in pulmonary function testing. Knowing the expected variation in bioQC data assists the detection of equipment errors but also enables the laboratory to identify what change in lung function is due to natural variability versus a real change in lung function.
Participation in multicenter clinical trials of new pulmonary medications and inhaled insulin is financially rewarding to the site’s principal investigators (usually pulmonary specialists), and the primary outcome measure is usually a PFT measurement like FEV1 or DLCO. Currently, each pharmaceutical company must develop its own PFT quality assurance program to minimize measurement noise within and between clinical sites. These studies are often done on more than one continent, making a worldwide accreditation program for PFT laboratories desirable.
In the United States, pulmonary function technologists can and should obtain the CPFT and RPFT credentials offered by the NBRC, but no program for the accreditation of PFT laboratories is available here. Such programs have been operational in the province of Ontario, Canada, and the countries of Australia and New Zealand for several years. We believe that these successful programs should be adopted by all other professional pulmonary societies.
The Thoracic Society of Australia and New Zealand (TSANZ) began to offer a voluntary PFT laboratory accreditation program in the 1990s. There are three steps: 1) a self-assessment questionnaire; 2) submission of the application forms, along with the laboratory procedure and policy manuals; and 3) a site visit by the accreditation assessment panel. Details of this process are available online at www.thoracic.org.au. The program includes reviews of staff qualifications and experience, laboratory policy, instruments, testing methods, and the quality assurance programs. So far, 18 PFT laboratoris in Australia and three in New Zealand have been accredited, and several others are in the process. TSANZ accreditation is valid for a period of 5 years.
In January 2007, representatives from several international respiratory societies attended the Association for Respiratory Technology and Physiology meeting in Glasgow, Scotland, to discuss worldwide PFT laboratory accreditation. The aim of a worldwide accreditation program is to improve the quality of pulmonary function testing by ensuring that staff are well trained to practice their profession and thereby produce high-quality results for the patients and clinicians they serve. In other words, any laboratory that attains the required accreditation standard has done so by proving it is up to speed, and this achievement has come from the laboratory staff. In preparation for such a program, take the CPFT or RPFT examination, prepare a manual of all the pulmonary function procedures done in your laboratory, and strengthen your quality assurance program.
Paul Enright, MD, is a pulmonary physician at the University of Arizona (e-mail: ). Maureen P. Swanney, PhD, is a respiratory scientist at Christchurch Hospital in New Zealand