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The carbon monoxide diffusing capacity: clinical implications, coding, and documentation.
1Medicine, Pulmonary, Allergy, and Critical Care Division, Emory University School of Medicine, Atlanta, GA.
The diffusing capacity of the lung for carbon monoxide (DLCO) test is valuable for diagnosing lung diseases. Billing code 94725 for membrane diffusing capacity has seen a surprising increase, likely due to financial incentives, and its use should be halted until clinically justified.
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Area of Science:
- Pulmonary Medicine
- Respiratory Physiology
Background:
- The diffusing capacity of the lung for carbon monoxide (DLCO) is a well-established pulmonary function test.
- Standardization guidelines exist to reduce variability in DLCO measurements.
- Billing codes 94720 (DLCO) and 94725 (membrane diffusing capacity) are used for reporting.
Purpose of the Study:
- To investigate the significant increase in the utilization of billing code 94725.
- To examine the potential reasons behind the surge in membrane diffusing capacity testing.
- To recommend a course of action regarding the clinical use and billing of code 94725.
Main Methods:
- Analysis of Medicare population data from 2000 to 2005.
- Comparison of utilization rates for billing codes 94720 and 94725.
- Discussion of potential explanations for observed trends.
Main Results:
- A >1,000% increase in Medicare claims using code 94725 between 2000 and 2005.
- Utilization of code 94725 increased 14 times faster than code 94720 during the study period.
- No current clinical indications exist for membrane diffusing capacity testing.
Conclusions:
- The dramatic rise in code 94725 billing is likely driven by financial gain, not clinical necessity.
- Billing and coding for membrane diffusing capacity (94725) should be discontinued until clear clinical indications are established.
- Healthcare providers must be prepared to justify the use of code 94725 to payers if it continues to be used.

