In this issue of CHEST (see page 663), Plummer1 provides a very useful and informative article on the carbon monoxide diffusing capacity (Dlco). The article covers clinical implications of the test, along with discussions of coding and documentation issues that may guide physicians to properly code for these tests.
The article also raises important questions about the use of current procedural terminology code 94725. This billing code is available to bill for components of Dlco, specifically the membrane diffusing capacity (Dmco). While measurements of Dmco and capillary blood volume (Vc) have long been used to shed light on the physiology of lung and heart diseases, this has not yet translated into clear clinical utility. The criteria for using them in clinical testing should include demonstration that they improve clinical care in patients by altering diagnosis or therapy in a way not accomplished with the tests currently used for patients with heart and/or lung diseases.