Introduction:

SAD is a precursor and key feature of chronic obstructive pulmonary disease (COPD). The lower limit of normal (LLN) and fixed ratio definition of FEV1/FVC may be discordant in up to 54% of cases, where there is potential for COPD misdiagnosis⁽¹⁾. Therefore, there is a clinical need to assess SAD in older people and determine whether this is pathological or part of normal aging.

Methods:

Healthy controls (n = 29) and mild to moderate COPD patients over 60 years old underwent lung function once within a prospective cohort study SAFFRON (IRAS ID 253739). COPD patients were classified as discordant (FEV₁/FVC >LLN; disCOPD; n =14) or concordant (FEV₁/FVC <LLN; conCOPD; n = 21). Analysis: one-way ANOVA or Kruskall-Wallis for parametric and non-parametric data respectively, categorical data using chi-squared test.

Results:

ConCOPD patients were younger (p=0.002) with mean TLco and Kco <80%pred (both p<0.001) and elevated TLC and FRC ( both p=0.001) implying that emphysema and hyperinflation are confined to this group. Established SAD markers were more aberrant in COPD v health, with lower FEV₁/FVC, lower MMEF_25-75, raised X_5Hz on impulse oscillometry and raised R_5-19 on Forced Oscillation Technique (all p?0.04). Notably disCOPD exhibited differences in oscillometry from health, and higher LCI (p=0.005).

Discussion:

There is no evidence of emphysema or hyperinflation on lung function in disCOPD patients, despite the presence of SAD, highlighting the potential for misdiagnosis of early COPD due to silent SAD. Radiology, blood biomarker and functional capacity data, collected as part of the SAFFRON study, will be of benefit.

Ref 1: 10.1136/thx.2008.098483