Background: History, clinical presentation, lung function testing, radiographs including HRCT and nonsurgical biopsy techniques in most cases provide sufficient information for classification of interstitial lung disease (ILD). However, in a small percentage it is not possible to establish the diagnosis so that lung biopsy may be required. We analyzed under which circumstances a reduction of invasive procedures is reasonable.
Methods: Between January 1997 and December 2009 we examined 3399 specimens from 1299 patients with benign inflammatory and granulomatous diseases in whom ILD was clinically hypothesized. We compared the probability of disease according to Bayes before and after surgery which corresponds to the clinical diagnosis (a priori probability) and the final diagnosis (a posteriori probability). Additionally, procedures, operation related complications and the patients' smoking habits were documented.
Results: In 111 patients (8.5 %) surgical evaluation was performed (14 mediastinoscopies, 97 thoracotomies/VATS biopsies). All mediastinoscopies substantiated a epitheloid cell granulomatosis. In 30 % of all VATS procedures a prolonged air leak of more than 4 days was observed. One patient died and one had to get a new chest tube after removal. Changes of a priori/a posteriori probabilities was shown for non-smokers in Wegner's granulomatosis (0.6 vs. 2.2 %) and IPF (16.7 vs. 34.8 %), for smokers in Langerhans' cell histiocytosis (1.4 vs. 7.8 %) and IPF (16.7 vs. 33.3 %). In the majority of cases even a reduction of probability was seen.
Conclusion: Considering complications and limited diagnostic gain, lung biopsies for diagnosis of ILD should be recommended only in selected patients.
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