The Non-invasive Diagnosis System Of Idiopathic Pulmonary Fibrosis And Nonspecific Interstitial Pneumonia

ObjectiveIdiopathic pulmonary fibrosis (IPF) and nonspecific interstitial pneumonia (NSIP) are two diseases of the highest incidence and the most easily confused in the idiopathic interstitial pneumonia (IIP). The purpose of this study is to review the clinical manifestations, pathology, high resolution computed tomography (HRCT), pulmonary function, bronchoalveolar lavage (BAL) and assess the role of those methods in differentiating IPF from NSIP in order to get an equation to assist the differential diagnosis between the IPF and NSIP.MethodsA retrospective review of 53 patients with IPF (n=23) and NSIP (n=30) was carried out. Prior to surgical lung biopsy, all of them underwent HRCT, pulmonary function test, blood gas analysis, and 39 cases of them underwent BAL. Clinical, physiologic, chest radiographic, and CT features were recorded. All statistical analyses were performed with statistical software (SPSS, version 13.0). A P value of less than 0.05 was considered to indicate a significant difference. The statistical methods of logistic regression and multiple linear regression are used to establish the equation. The method of curve fitting is used to find the critical value of the equation to assist the differential diagnosis between the IPF and NSIP.Results1) Compared to NSIP, the patients of IPF are older, more males than females, having a bigger proportion of smokers, enduring longer time before they visit the hospital.2) Hypoxemia and diffusion dysfunction occur in both the patients of IPF or NSIP; however FEV₁/FVC are normal. There is no significant difference between the IPF and NSIP.3) The most common sign in the HRCT of IPF is reticular pattern, followed by honeycombing. As to NSIP, the most common sign in the HRCT is ground-glass opacities, followed by reticular pattern. The signs of honeycombing and reticular pattern are more seen in IPF than NSIP whereas the signs of ground-glass opacities and consolidation are less seen in IPF than NSIP. There are many overlaps in the signs of HRCT between IPF and NSIP.4) Neutrophil count in BAL fluid was higher in IPF than NSIP. In contrast, BAL lymphocyte count was significantly higher in NSIP than IPF. BAL lymphocytosis was more frequently observed in NSIP than IPF and the absence of BAL lymphocytosis suggested a diagnosis of IPF rather than NSIP.5) Using the traditional clinical-radiology diagnosis method, the ratio of first diagnosis correctness in IPF is 85.7%, as to NSIP is 61.1%. The most confused is the diagnosis between IPF and FM-NSIP.6) We adopt the score methods of HRCT and the equation: Y= 0.9+0.123X1—0.045X2+0.009X3+0.033X4 to improve the traditional clinical-radiology diagnosis method. The new method can assist the differential diagnosis between the IPF and NSIP in this group of patients.ConclusionClinical, HRCT and BAL are useful non-invasive tools in diagnosis IPF and NSIP. The equation: Y= 0.9+0.123X1-0.045X2+0.009X3+0.033X4 can assist the differential diagnosis between the IPF and NSIP.