Radiological versus histological diagnosis in UIP and NSIP: survival implications

Background: High resolution computed tomography (HRCT) has an important diagnostic role in idiopathic interstitial pneumonia (IIP). We hypothesised that the HRCT appearance would have an impact on survival in patients with IIP. Methods: HRCT scans from patients with histological usual interstitial pneumonia (UIP; n=73) or histological non-specific interstitial pneumonia (NSIP; n=23) were characterised as definite UIP, probable UIP, indeterminate, probable NSIP, or definite NSIP. Cox regression analysis examined the relationships between histopathological and radiological diagnoses and mortality, controlling for patient age, sex, and smoking status. Results: All 27 patients with definite or probable UIP on HRCT had histological UIP; 18 of 44 patients with probable or definite NSIP on HRCT had histological NSIP. Patients with HRCT diagnosed definite or probable UIP had a shorter survival than those with indeterminate CT (hazards ratio (HR) 2.43, 95% Cl 1.06 to 5.58; median survival 2.08 v 5.76 years) or HRCT diagnosed definite or probable NSIP (HR 3.47, 95% Cl 1.58 to 7.63; median survival 2.08 v 5.81 years). Patients with histological UIP with no HRCT diagnosis of probable or definite UIP fared better than patients with histological UIP and an HRCT diagnosis of definite or probable UIP (HR 0.49, 95% Cl 0.25 to 0.98; median survival 5.76 v 2.08 years) and worse than those with a histological diagnosis of NSIP (HR 5.42, 95% Cl 1.25 to 23.5; median survival 5.76 v >9 years). Conclusions: Patients with a typical HRCT appearance of UIP experience the highest mortality. A surgical lung biopsy is indicated for patients without an HRCT appearance of UP to differentiate between histological UIP and NSIP.