A Sensitive CT-Based Morphologic Method to Monitor Pulmonary Changes of Cystic Fibrosis
A Sensitive CT-Based Morphologic Method to Monitor Pulmonary Changes of Cystic Fibrosis
Abstract & commentary
Synopsis: A morphologic CT-based system is proposed for evaluation and follow-up of patients with cystic fibrosis. The CT scores correlated significantly with pulmonary function test results, serum immunoglobulin levels, and clinical scores.
Source: Helbich TH, et al. Cystic fibrosis: CT assessment of lung involvement in children and adults. Radiology 1999; 213:537-544.
The accuracy and efficacy of using thin sec-tion CT of the chest to monitor and predict the status of patients with cystic fibrosis (CF) has been translated into a quantitative scoring system for morphologic abnormalities.
This study compared an expanded computed-tomographic-based scoring system for CT morphologic abnormalities with accepted nonmorphologic indexes of pulmonary status including pulmonary function tests, the Shwachman-Kulczycki clinical scoring system, immunoglobulin status, and chromosomal genotype. Using a CT-based classification system could become routine in follow-up evaluation of CF patients.
Helbich and associates examined 117 patients with CF with CT studies consisting of scans of 2-mm-thick or 1.5-mm-thick sections at 10-mm intervals from the lung apices to below the costophrenic angles. Images were obtained at end-inspiration volume in cooperative patients or during quiet respiration.
The radiologists determined the grade and anatomic distribution of the following signs: severity and extent of bronchiectasis, peribronchial wall thickening, extent of mucous plugging, extent of sacculations or abscesses, generations of bronchial divisions involved, severity of bullae, emphysema, and mosaic perfusion, collapse, or consolidation. The pulmonary function tests used were forced vital capacity, forced expiratory volume in the first, second, and maximum expiratory flow. The patient’s clinical status was determined using general activity, physical examination of the thorax, and nutrition status.
Morphologic CT changes most frequently observed were bronchiectasis (80%), peribronchial wall thickening (76%), mosaic perfusion (64%), and mucous plugging (51%). Evaluation by three age groups—0-5 years, 6-16 years, and 17 years and older—demonstrated significant trends for progression of disease as determined by the CT score. There was a significant score increase for all CT abnormalities between each of the three age groups. Pulmonary function test results could not demonstrate significant changes between groups 1 and 2. The clinical scoring system also failed to indicate any progression between groups 1 and 2. For both pulmonary function tests and clinical score, there was a significant increase for patients age 17 and older.
The CT scores correlated better with the measures of obstructive pulmonary function than with the measures of hyperinflation, and the CT scores correlated with serum immunoglobulin levels. The CT findings did not differ significantly between two genotypes.
The proposed expanded CT scoring system provides a useful method of monitoring status of disease and progression in patients with CF. CT may be more sensitive than nonmorphologic parameters; thus, CT could be incorporated into the routine follow-up evaluation of these patients.
Comment by Beverly P. Wood, MD
This article demonstrates an extremely important correlation between the morphologic appearances of CF by CT examination and its role as a method of staging CF and prediction. Chest radiographs are usually used as a method of evaluation of CF and were not used in this study. However, the comparison of significance of CT scoring with the pulmonary function results (particularly the determinants of obstructive changes) suggests that this method could be incorporated into the routine assessment and follow-up of CF patients as a reliable indicator of patient pulmonary status.
One limitation in the study is the homogeneity of the patient groups examined. Both homozygous and heterozygous patients with CF were studied, but there are a large number of mutations of the CF gene, and a much larger study would be of assistance in determining the use of CT as a predictor in this much larger patient population. An interesting finding in this study is the increased sensitivity of CT over pulmonary function testing and clinical status in the two groups of children ages 0-5 years and 6-16 years. As this is expected to be the time of disease progression, I would have expected the nonmorphologic scoring to demonstrate a progression of disease more frequently.
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