Epidemiology Of Interstitial Lung Disease (IlD)

SummaryWorldwide almost no epidemiologic data are available on the prevalence orincidence of interstitial lung diseases (ILD) in the general population. Therefore, a registration programme of ILD-prevalence was organised by the VRGT (Vercniging voor Respiratoire Gezondheidszorg en Tuberculosebestrijding), among about 100 Flemish pneumologists since 1990.Most categories of the classification by Crystal et al. (1) were included and the diagnostic criteria (histology, laboratory tests, clinic, radiology) were registered. The present paper presents the results of 1992–1994: twenty pneumologists had forwarded the summary files of 237 patients to the central office in 1992 (n=68), 1993 (n=90) and 1994 (n=79).The diagnoses that were most frequently made were: sarcoidosis in 27%, idiopathic pulmonary fibrosis in 20%, hypersensitivity pneumonitis in 14% (of which 68% by birds) and collagen-vascular disease in 10% (of which 54% in rheumatoid arthritis). Less frequent causes were eosinophilic pneumonia (4%), inhalation of inorganic material (4%, anthracosilicosis being excluded), histiocytosis X (3%), drugs (3%), angiitis and granulomatosis (2%), pulmonary hemosiderosis (1%), lymphocytic infiltrative lung disease (1%) and lymphangioleiomyomatosis (1%). The order of relative frequencies of the different categories of diseases was the same in the 3 registration years. In 9% of the patients the diagnosis was confined to “undefined fibrosis”. The diagnosis was confirmed by histology in 63% of the cases. The overall male-female ratio was nearly one, with, however, a male preponderance in hypersensitivity pneumonitis (22/12), UIP(8/3) and “undefined fibrosis” (14/7). All age groups were represented but 65% of the patients were over 50 years old. Analysis of the postal codes showed following regional distribution (for the whole study period): 51 patients lived in Flemish Brabant, 111 in Antwerp, 31 in Limburg, 24 in East-Flanders, and 13 in West-Flanders.Although this registration undoubtedly underestimates the real prevalence of interstitial lung diseases and may contain some bias due to different approaches among the participating centers (despite the instructions in the protocol), it provides important information on the relative frequency of the different forms.