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PREDICTING IPF VS NSIP WITHOUT A SURGICAL LUNG BIOPSY

University of Calgary, Calgary, AB, Canada

PURPOSE: The presence of significant honeycombing on HRCT, in the right clinical context, can suggest a definitive diagnosis of IPF. However, in patients with minimal or no honeycombing (ie, a HRCT Fibrosis score ;1.0), it is often difficult to differentiate IPF from NSIP without a lung biopsy. However, many patients are elderly or have comorbidities preventing surgical lung biopsy. The aim of this study is to determine if clinical data can predict a diagnosis of IPF (UIP) vs. NSIP without a lung biopsy.

METHODS: This is a retrospective analysis of patients in the database of the University of Michigan Specialized Center of Research in Fibrotic Lung Disease. All patients had a surgical lung biopsy reviewed by two pulmonary pathologists. HRCTs were scored by two thoracic radiologists following criteria by Kazerooni et al (1997) for the presence of interstitial disease (Fibrosis score) or ground glass opacification (Alveolar score) on a scale of 0-5. We selected cases with mean CT Fibrosis scores ;1.0 as these have less honeycombing, and are thus more difficult to interpret, than HRCTs with higher scores. PFTs, HRCTs, and 6MWTs were performed within 6 months of the biopsy.

RESULTS: Data are from 79 patients with a histopathologic diagnosis of UIP (n=66) or NSIP (n=13) and a mean HRCT Fibrosis score of 1.0 or less. Patients with UIP were older (63±8 vs. 52±8, p<.005), had more fibrosis on HRCT (.80±.2 vs .55±.3, p=.003), and more likely to be male (46/66 vs 4/13, p=.008). Exploratory analysis showed several cutpoints with high specificity in predicting a diagnosis of UIP (Table 1).

CONCLUSION: Age >70, CT Alveolar score >1.0, desaturation <88% during 6MWT, and FVC ; 40% predicted are more predictive of a diagnosis of UIP in patients with CT evidence of fibrosis but little or no honeycomb change.

CLINICAL IMPLICATIONS: These results will enable physicians to predict a diagnosis of IPF or NSIP for patients in whom a surgical lung biopsy is not feasible or desired.

DISCLOSURE: Charlene Fell, No Financial Disclosure Information; No Product/Research Disclosure Information