Long-term intersession variability for single-breath diffusing capacity

Area of Science:

• Pulmonary Function Testing
• Biomedical Engineering
• Quality Control in Healthcare

Background:

• Assessing long-term diffusing capacity (DL(CO)) variability is crucial for equipment quality control and patient management.
• Previous research has not reported on long-term DL(CO) variability.

Purpose of the Study:

• To characterize the long-term variability of DL(CO) in a biocontrol cohort.
• To compare different methods for selecting a target DL(CO) value for variability assessment.

Main Methods:

• Longitudinal DL(CO) monitoring of 288 biocontrols over up to 5 years, with twice-monthly testing.
• Standardized DL(CO) measurement technique used throughout the study.
• Variability analysis using three distinct target value selection methods.

Main Results:

• The 90th percentile for mean intersession DL(CO) change ranged from 10.9% to 15.8% (2.6-4.1 units).
• Lowest variability was observed when using the mean of all tests as the target; highest variability occurred when using the baseline DL(CO).
• The average of the first six DL(CO) tests accurately estimated the mean DL(CO) value, yielding a 90th percentile change of 12.3% (3.0 units).

Conclusions:

• DL(CO) deviations exceeding 12% or 3.0 units from the average of the first six tests indicate potential instrument quality control issues.
• Instruments showing such deviations require careful evaluation before further patient testing.
• Variability remained stable over time and was not significantly associated with demographic factors.