Restrictive spirometry versus restrictive lung function using the GLI reference values

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology
• Diagnostic Accuracy

Background:

• Restrictive lung function can indicate various underlying diseases.
• Accurate identification of restrictive lung function is crucial for diagnosis and management.
• Global Lung Function Initiative (GLI) provides reference values for lung function parameters.

Purpose of the Study:

• To evaluate the accuracy of different restrictive spirometry patterns (RSPs) in identifying restrictive lung function (TLC < LLN).
• To compare traditional RSP definitions with those derived from Youden's method.
• To assess RSP accuracy against GLI reference values in a general population sample.

Main Methods:

• A general population sample (n=607, ages 23-72) with spirometry and TLC measurements was analyzed.
• Two categories of RSPs were evaluated: traditional definitions and Youden's method-derived definitions.
• Accuracy metrics (sensitivity, specificity) were calculated for each RSP definition.

Main Results:

• The prevalence of restrictive lung function (TLC < LLN) was 5.3%.
• The most accurate cut-offs for FVC to identify TLC < LLN were 85.5% of predicted and a Z-score of -1.0.
• Traditional RSPs showed high specificity but low sensitivity compared to Youden's method-derived RSPs.

Conclusions:

• RSP definition FVC < LLN and FEV1/FVC ≥ LLN demonstrated high specificity, suitable for ruling out restrictive lung function.
• RSP definition FVC < 85.5% predicted and FEV1/FVC ≥ LLN offers a favorable balance of sensitivity and specificity for screening.