CT scan scores for each scoring system component and a composite CVID airway, CVID parenchyma/interstitial, and a CVID all items CT scan score were normalized to a 0% to 100% scale as follows. For bronchiectasis and airway wall thickening for each lobe, the most severe score (maximum 3) is added to the average score (maximum 3), and the sum is multiplied by the extent score (maximum 3). This leads to a maximum raw score of 18 points per lobe and 108 points per six lobes. To normalize the score onto a range of 0% to 100%, the bronchiectasis score and airway wall thickening score are multiplied by the normalization factor 100/108. For all other inspiratory CT scan lung items (mucus plugging, tree-in-bud, nodules, septa thickening, ground glass, opacity, bulla/cysts), the maximum score per lobe is 3 and the maximum raw score per six lobes is 18. To normalize these scores to a range of 0% to 100%, these scores are multiplied by the normalization factor 100/18. A combined mucus score was calculated by summing the mucus plugging scores (maximum per lobe 3) and tree-in-bud scores (maximum per lobe 3); the maximum score for the six lobes was therefore 36 and the normalization factor 100/36. For expiratory air trapping, the maximum score per lobe was 5 and the maximum score per six lobes 30. The normalization factor for air trapping was therefore 100/30. The CVID airway disease score was calculated by adding the normalized bronchiectasis score, airway wall thickening score, combined mucus score, and air trapping score. The maximum score was therefore 400 and the normalization factor 100/400. The CVID parenchyma/interstitial disease score was calculated by adding the normalized opacities, ground glass, nodules, and septa scores. We excluded the bulla and cyst score, as this item was always scored as 0%. The theoretical maximum is 400, but in practice, ground glass and opacities/consolidations cannot be scored both for the same area in the lungs. The normalization factor that was used was therefore 100/300. Finally, an overall CVID composite score was calculated by adding the normalized bronchiectasis, airway wall thickening, combined mucus, air trapping, opacities, ground glass, septa, and nodules scores. The theoretical maximum is 800, but since in practice opacities and ground glass cannot be scored simultaneously in a given area we used 100/700 as the normalization factor.