In: Health1 Apr 2014
The expiratory images were assessed for the presence and lobar distribution of air trapping. The criteria used to diagnose the presence of air trapping were alteration of normal anteroposterior lobar attenuation gradients and/or lack of homogeneous increase in lung attenuation resulting in persistent areas of hypoattenuation. The extent of air trapping was quantified and categorized using the same system as defined for hyperlucent regions on inspiratory images. As limited air trapping has been reported as a finding in normal individuals, the presence of air trapping was noted, scored, and considered indicative of BO in study patients only when its extent exceeded 25% of the crosssectional area of an affected lung on at least one scan level. Expiratory images displayed at standard and narrow window settings were directly compared to determine differences in the conspicuity of air trapping.
Spirometry was obtained in all patients within a mean time interval of 1.3 days (range, 0 to 10 days) from time of CT examination. Using criteria established by the International Society for Heart and Lung Transplantation (ISHLT), patients were assessed and staged for bronchiolitis obliterans syndrome (BOS): stage 0 (FEV1? >80% of baseline value); stage 1 (FEV1, 66 to 80% of baseline value); stage 2 (FEV1, 51 to 65% of baseline value); and stage 3 (FEVl9 >50% of baseline value).
Statistical comparison of the frequency of HRCT findings between patients with and without BO was performed using Fisher’s Exact Test. Correlation between the air trapping score and clinical stage of BOS was assessed by the Spearman rank correlation test.
Bronchiectasis was present in 6 of 21 (29%) patients and had a sensitivity of 36%, specificity of 80%, and accuracy of 57% for BO (Table 1). The frequency of bronchiectasis found in patients with (4/11, 36%) and without (2/10, 20%) BO was not significantly different (p>0.05). Mosaic pattern of lung attenuation, identified in 8 of 21 (38%) patients, occurred more frequently in patients with BO (p<0.05) with a sensitivity of 64%, specificity of 90%, and an accuracy of 76% (Table 1 and Fig 1). On the inspiratory images, the extent of low-attenuation regions was scored as 1 (<10% of lung affected) in three patients and 2 (10 to 25% of lung affected) in five patients.
Table 1—Comparison of HRCT Findings in Lung Transplant Recipients With and Without RO
|Finding||BO Positive n=ll (%)||BO Negative n= 10 (%)||p Value|
Figure 1. A 24-year-old heart-lung transplant recipient with BO. HRCT scan of the right lung obtained at suspended full inspiration shows a mosaic pattern, with alternating lobules of lower (curved arrows) and higher (straight arrow) attenuation.
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