Article Text

Download PDFPDF
Validation of computed tomographic lung densitometry for monitoring emphysema in α1-antitrypsin deficiency
  1. D G Parr1,
  2. B C Stoel2,
  3. J Stolk3,
  4. R A Stockley1
  1. 1Lung Investigation Unit, Queen Elizabeth Hospital, Birmingham B15 2TH, UK
  2. 2Division of Image Processing, Department of Radiology, Leiden University Medical Centre, Leiden, The Netherlands
  3. 3Department of Pulmonology, Leiden University Medical Centre, Leiden, The Netherlands
  1. Correspondence to:
    Professor R A Stockley
    Lung Investigation Unit, First Floor, Nuffield House, Queen Elizabeth Hospital, Birmingham B15 2TH, UK; r.a.stockley{at}bham.ac.uk

Abstract

Background: Lung densitometry derived from computed tomographic images offers an opportunity to quantify emphysema non-invasively, but a pathological standard cannot be applied to validate its use in longitudinal monitoring studies. Consequently, forced expiratory volume in 1 second (FEV1) remains the standard against which new methods must be judged. We related progression of densitometry (15th percentile point and voxel index, threshold −950 Hounsfield units) to disease stage and FEV1 decline in two studies of subjects with α1-antitrypsin deficiency (PiZ).

Methods: Consistency of progression, measured using densitometry and FEV1, was assessed in relation to disease stage in a 2 year study of 74 subjects grouped according to the FEV1 criteria employed in the GOLD guidelines. In the second study of a subgroup of subjects with extended data (n = 34), summary statistics were applied to measurements performed annually over 3 years and the rate of progression of densitometry was related to FEV1 decline.

Results: The progression of percentile point was consistent across a wide spectrum of disease severity, but voxel index progression varied in association with disease stage (p = 0.004). In the second study, FEV1 decline correlated with progression of lung densitometry (percentile point: rS = 0.527, p = 0.001; voxel index: rS = −0.398, p = 0.012).

Conclusions: 15th percentile point is a more consistent measure of lung density loss across a wide range of physiological impairment than voxel index. However, both methods are valid for use in longitudinal and interventional studies in which emphysema is the major outcome target.

  • AATD, α1-antitrypsin deficiency
  • CT, computed tomography
  • FEV1, forced expiratory volume in 1 second
  • HU, Hounsfield units
  • Perc15, 15th percentile point
  • VI, voxel index
  • lung densitometry
  • computed tomography
  • emphysema
  • alpha1-antitrypsin deficiency

Statistics from Altmetric.com

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.