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Letters to the Editor |
Departments of Radiology* and Medicine, Division of Pulmonary and Critical Care Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Kangnam-Ku, Seoul 135-710, South Korea
Editor:
We read an interesting article by Dr Johkoh and colleagues in the May 1999 issue of Radiology (1). In this article, two observers assessed thin-section computed tomographic (CT) scans of 129 patients with histopathologically proved idiopathic interstitial pneumonia. The correct diagnosis was made in a mean of 25 of 35 (71%) cases of usual interstitial pneumonia (UIP), 19 of 24 (79%) cases of bronchiolitis obliterans organizing pneumonia (BOOP), 14.5 of 23 (63%) cases of desquamative interstitial pneumonia (DIP), 13 of 20 (65%) cases of acute interstitial pneumonia (AIP), and 2.5 of 27 (9%) cases of nonspecific interstitial pneumonia with fibrosis (NIPF). They concluded that, except for NIPF, the various subtypes of idiopathic interstitial pneumonia often have a characteristic appearance that allows differentiation at thin-section CT.
We raise several questions on the article. First, Dr Johkoh and colleagues collected 129 cases of idiopathic interstitial pneumonia from five institutions. We are concerned with the histopathologic diagnosis regarding these cases. NIPF is a new histopathologic diagnostic entity suggested by Katzenstein and Fiorelli in 1994 (2). Therefore, Dr Johkoh and colleagues should not have included in their study the cases diagnosed before 1994 unless they reevaluated all pathologic specimens according to the new classification scheme. Some of the cases diagnosed before 1994 might have been forcefully fit into one of the four categories of idiopathic interstitial pneumonia; in particular, the cases of NIPF might have been classified as UIP.
Second, the 129 cases studied by Dr Johkoh and colleagues do not seem to represent the overall prevalence of idiopathic interstitial pneumonia. According to a report by Bjoraker et al (3) and our experience, UIP is the most common disease, followed by NIPF, BOOP, AIP, and DIP. Awareness of the overall prevalence of each disease entity could have enhanced the diagnostic accuracy of thin-section CT.
Third, the observers in Dr Johkoh and colleagues' study had a different insight on NIPF from ours. They assessed NIPF with the knowledge that it appears as patchy areas of ground-glass opacity, usually with lower-zonal predominance, and may show airspace consolidation or interlobular reticulation. According to a recent article (4), NIPF appears as patchy subpleural areas of ground-glass opacity plus an irregular linear opacity with lower-zonal predominance. This distribution of parenchymal abnormalities is very similar to that for UIP and DIP, which can be observed in table 3 of the article by Dr Johkoh and colleagues (1).
UIP, NIPF, and DIP have lower-zonal and subpleural distributions. UIP appears at CT as areas of ground-glass opacity, irregular linear opacity, and honeycombing. NIPF appears as areas of ground-glass opacity and irregular linear opacity, sometimes with an area of consolidation. Honeycombing is rarely seen (4). DIP is a rare disease and is characterized by ground-glass opacity with some areas of irregular linear opacity. AIP, with patchy or diffuse, mixed ground-glass opacity and consolidation, shows random distribution. BOOP, with a main pattern of consolidation, shows subpleural and/or peribronchovascular distributions. In addition, we cannot emphasize too much the need to consider the overall prevalence of idiopathic interstitial pneumonia to make such a diagnosis at CT.
We believe that integration of the pattern and distribution of parenchymal abnormalities at thin-section CT and knowledge of the overall prevalence of idiopathic interstitial pneumonia would help increase the diagnostic accuracy of thin-section CT in the differential diagnosis of the disease and would result in better accuracy than that in the study by Dr Johkoh and colleagues (1).
References
Department of Radiology, Osaka University Medical School, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
I thank Drs Lee and Chung for their letter regarding the article by me and my colleagues (1). I answer their questions as follows:
First, all cases included in our study were reevaluated in the light of recent diagnostic criteria on each disease after 1994, when Katzenstein and Fiorelli's article (2) on NIPF was published.
Second, I agree with the opinion of Drs Lee and Chung. Of course, in daily clinical practice, we perform differential diagnosis by considering the prevalence of each disease. However, the purpose of this study was just to evaluate the superiority of CT as a diagnostic tool for idiopathic interstitial pneumonias. As such, we do not need to consider the overall frequency of each disease entity.
Third, when we submitted our article, we could not reference the article by Drs Lee and Chung and colleagues (3) because it had not yet been published. Therefore, our description of the appearance at CT of NIPF was derived from their previous article (4). The results in both articles regarding characteristic CT findings of NIPF are not as inconsistent as Drs Lee and Chung suggest in their letter. However, if our two readers had had the benefit of their more recent article (3), the diagnosis of NIPF would have been more accurate.
We also believe that integration of the pattern and distribution of parenchymal abnormalities at thin-section CT and knowledge of the overall prevalence of idiopathic interstitial pneumonia would help increase the diagnostic accuracy of thin-section CT in the differential diagnosis of the disease. However, the purpose of our study was just to evaluate the superiority of CT as a diagnostic tool for idiopathic interstitial pneumonias, with the exclusion of other factors such as overall prevalence. In that regard, the value of our article is clear, we believe.
References
This article has been cited by other articles:
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  N. Kaminski, J. A. Belperio, P. B. Bitterman, L. Chen, S. W. Chensue, A. M.K. Choi, S. Dacic, J. H. Dauber, R. M. du Bois, J. J. Enghild, et al. Idiopathic Pulmonary Fibrosis Am. J. Respir. Cell Mol. Biol., September 1, 2003; 29(3): S1 - 105. [Full Text] [PDF]
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