Study objectives: Using semiquantitative scoring methods, several studies have shown that the amount of fibroblastic foci (FF), which are one of the pathologic characteristics in usual interstitial pneumonia (UIP), is a significant prognostic factor of UIP. In those studies, the degree of FF was evaluated semiquantitatively on several scales by a panel of pulmonary pathologists. However, the evaluation was somewhat subjective because interobserver variation was not small. Additionally, these methods are not entirely practical because two or more pathologists are required. In this study, we tried to develop a more quantitative scoring method of FF.
Patients and methods: With a charge-coupled device camera, we made images of lung sections obtained from 15 patients with UIP associated with collagen vascular disease (CVD) [CVD-UIP] and 16 patients with idiopathic pulmonary fibrosis (IPF) [IPF/UIP], and calculated the proportion of FF areas in the target image areas with an image analytic software.
Measurements and results: Our quantitative scoring method enabled us to readily and objectively evaluate the extent of FF as a quantitative percentage of FF area (%FF) score. Interobserver and intraobserver correlations were high in our method (r = 0.877 and r = 0.898, respectively). The quantitative %FF score (+/- SD) of IPF/UIP patients was 1.67 +/- 0.90%, which was significantly higher than that of CVD-UIP patients (0.39 +/- 0.24%, p < 0.0001). A Cox proportional hazards model showed that the quantitative %FF score was a significant predictor of survival in UIP patients. The quantitative %FF score had a correlation with scores assessed by the semiquantitative scoring methods previously reported, but patients with the same score assessed by the semiquantitative methods had widely varying scores assessed by our method.
Conclusions: These results suggest that our quantitative scoring method for FF is more objective than the semiquantitative scoring methods previously reported, providing accurate information about the prognosis of patients with UIP.