The histopathologic pattern provides the most important prognostic marker for idiopathic interstitial pneumonia; however, studies have suggested that short-term changes in lung function may be more important. We investigated the prognostic factors for fibrotic interstitial pneumonia. The clinical features and follow-up course of 179 patients (131 with idiopathic pulmonary fibrosis and 48 with nonspecific interstitial pneumonia; 41 fibrotic types and 7 cellular) were analyzed retrospectively. The lung function indices improved or stabilized in most patients with fibrotic nonspecific interstitial pneumonia in contrast to the deterioration or stable condition of most patients with idiopathic pulmonary fibrosis. The 5-year survival of patients with fibrotic nonspecific interstitial pneumonia (76.2%) was better than for those with idiopathic pulmonary fibrosis (43.8%) (p = 0.007). Multivariate analysis at the time of presentation revealed that pathologic pattern, age, and diffusion capacity had important prognostic implications. However, after 6 months of follow-up, changes in FVC, initial diffusion capacity, and sex were the only independent prognostic factors, with no additional prognostic information conferred by the histologic diagnosis. Our data confirmed the importance of physiological parameters including short-term change in FVC. However, at the time of diagnosis, histopathology was important for the prediction of prognosis and future change in lung function.

Keywords: fibrotic nonspecific interstitial pneumonia; idiopathic pulmonary fibrosis; prognostic factor; pulmonary function; surgical lung biopsyIn 1994, Katzenstein and Fiorelli proposed the term "nonspecific interstitial pneumonia" (NSIP) to describe a subset of idiopathic interstitial pneumonia (IIP) that could not be classified into any of the other types of interstitial pneumonia. They subcategorized the disease into three subgroups depending on the relative amounts of interstitial fibrosis and inflammation (1). Subsequently a number of other studies showed that an NSIP pattern in a surgical lung biopsy provided important prognostic information compared with other IIPs (2-7). However, there was considerable overlap in outcome, especially between patients with fibrotic NSIP and those with idiopathic pulmonary fibrosis (IPF) (2, 3, 8). Nicholson and coworkers showed that the prognosis of patients with fibrotic NSIP was less favorable than previously thought (3). They reported that the 5-year survival rate of patients with fibrotic NSIP was about 45%, which was worse than that reported by Travis and coworkers (2), although it was better than IPF (3). Therefore, Latsi and coworkers combined the fibrotic type NSIP and usual interstitial pneumonia (UIP) into fibrotic IIP (8). Several reports, including that of Latsi and co-workers, suggested that physiological parameters, especially short-term changes, were important in determining the prognosis for patients with IIP (8-12). These data may raise questions about the necessity for a pathologic diagnosis by surgical lung biopsy in the case of fibrotic IIP. However, accurate clinico-radiologic-pathologic diagnosis is crucial, especially at the time of diagnosis for initial management of patients with IIP. We therefore compared the importance of pathologic patterns in the prognosis for patients with fibrotic IIP (fibrotic NSIP pattern and UIP pattern) with physiological parameters including short-term change of lung function. We also compared the prognosis for those patients with IIP, especially fibrotic NSIP, with those for patients with IPF. Some of the results of this study have been previously reported in the form of an abstract (13).

METHODS

Subjects

Subjects included 179 patients with idiopathic NSIP or IPF diagnosed by surgical lung biopsy from January 1990 to September 2002 at Asan Medical Center, a 2,000-bed university-affiliated tertiary referral center in Seoul, South Korea. Two lung pathologists (M.K. and T.V.C.) reviewed the specimens independently. If the opinions of the two pathologists were different (coefficient of agreement k = 0.59), a third opinion was sought and the final diagnosis was made in the context of clinicoradiologic findings. There were 207 patients with IIP who had had surgical lung biopsies. Twenty-eight cases were excluded because of a failure to obtain consensus between the pathologists (9 cases) or because the patients were diagnosed as having other diseases (19 cases). NSIP was subclassified into cellular and fibrotic types, according to the level of fibrosis and inflammation (1).

Methods Used

Clinical data were obtained from medical records and survival status was obtained from telephone interviews and/or medical records. The minimal amount of smoking for a smoker was 1 pack-year, and an exsmoker was defined as a subject who had not smoked for at least 3 months (3). Patients were excluded if they had taken drugs, experienced occupational or other environmental exposures, or presented evidence of collagen vascular diseases on the basis of a thorough history, physical examination, and serologic tests.