Systematic review of the relevance of CT densitometry in patients with COPD and AATD

Introduction Quantitatively measuring the severity of emphysema in patients with COPD and AATD by CT densitometry is rapidly being recognised as an accurate and sensitive measure of disease stage and progression. We aim to elucidate the utility and interpretation of densitometry objectively through a new systematic review, and to establish the minimally clinically important difference (MCID) in density decline. An MCID for FEV1 and SGRQ in COPD is already well established, but in AATD specifically, this MCID should indicate those patient with significant net tissue loss and therefore consideration of further therapies. Methods We conducted an extensive and robust systematic review adhering to the Cochrane guidelines, with care to include all relevant studies, to eliminate bias and to meta-analyse appropriate results Results Due to wide variable outcome measures reported in both the measure of density i.e. differing %LAA (low attenuation areas) or the 15 th percentile point, a narrative meta-analysis was conducted where necessary. We propose an MCID incorporating important clinical variables such as lung function, and quality of life measures. Conclusion. The MCID of CT quantified density change will provide a useful additional tool in assessing patients with emphysema, and to potentially identify earlier those patients who are rapid decliners.