Lung function estimates in idiopathic pulmonary fibrosis: the potential for a simple classification

Application of a classification based on simple lung function testing in IPF For many years the idiopathic pulmonary fibrosis (IPF) community has debated the merits of the histopathological classification of idiopathic interstitial pneumonia (IIP).1 The ATS/ERS consensus statement identifies the importance of histological categories of usual interstitial pneumonia (UIP) and non-specific interstitial pneumonia (NSIP). Furthermore, it emphasises that IPF is the clinical correlate of UIP. Despite the recognition of the importance of histological characterisation, surgical biopsy rates vary considerably.2 Most clinicians do not subject their patients to surgical biopsy, despite the potential prognostic benefit of detailed histological evaluation, because many patients are elderly and have significantly impaired lung function and other medical co-morbidities resulting in a potentially high mortality rate.3 In addition, HRCT scanning provides diagnostic data of high sensitivity and specificity for the diagnosis of IPF with acceptable interobserver variability.4,5 Meanwhile, the chronic obstructive pulmonary disease (COPD) and lung transplantation communities have applied simple but pragmatically useful classifications. Bronchiolitis obliterans syndrome (BOS), for example, has been subject to a clinical grading system reflecting the degree of impairment of lung function following lung transplantation. The emergence of a classification based on simple lung function testing occurred because of the difficulties in obtaining adequate tissue for the diagnosis of obliterative bronchiolitis. This is comparable to the situation in IPF where tissue is also difficult to obtain. The success of the classification of BOS is reflected by the publication of an updated version.6 The global initiative for COPD (GOLD) is another example of a consensus classification based on simple lung function testing. GOLD provides a staging system ranging from an “at risk” category to a severe disease category.7 Based on simple lung function testing, it is reproducible and has facilitated the identification of patients with …