Are reference equations for spirometry an appropriate criterion for diagnosing disease and predicting prognosis?

Area of Science:

• Pulmonary Medicine
• Clinical Diagnostics
• Biostatistics

Background:

• Debate exists regarding fixed threshold criteria for diagnosing obstructive lung disease using FEV1 and FEV1/FVC ratios.
• Concerns have been raised about potential misclassification due to current diagnostic criteria.
• Critiques of existing criteria are often based on flawed assumptions about the validity of reference equations for normality.

Purpose of the Study:

• To critique the current methods for deriving reference equations used in lung function testing.
• To propose a novel interpretative approach for clinical use of lung function data.
• To advocate for the development of prognostic equations for diagnosing obstructive lung disease.

Main Methods:

• Analysis of the methodologies used to derive current reference equations for lung function.
• Critique of the arbitrary and potentially biased criteria in reference equation development.
• Proposal for prognostic equations analogous to cardiovascular risk factor equations.

Main Results:

• Current reference equations for lung function tests are derived using flawed methods, including arbitrary exclusion criteria and non-representative populations.
• Predictive variables in current equations may actually be risk factors for disease, leading to misinterpretation.
• A new approach using prognostic equations derived from cohort studies and RCTs is suggested.

Conclusions:

• The established methods for deriving reference equations for lung function tests are fundamentally flawed.
• A paradigm shift towards prognostic equations, similar to cardiovascular risk assessment, is necessary for accurate interpretation of lung function data.
• This new approach promises to enhance clinical decision-making in the diagnosis and management of obstructive lung disease.