EPIDEMIOLOGY OF INTERSTITIAL LUNG-DISEASE (ILD) IN FLANDERS - REGISTRATION BY PNEUMOLOGISTS IN 1992-1994

Worldwide almost no epidemiologic data are available on the prevalence or incidence of interstitial lung diseases (ILD) in the general popul ation. Therefore, a registration programme of ILD-prevalence was organ ised by the VRGT (Vereniging voor Respiratoire Gezondheidszorg en Tube rculosebestrijding), among about 100 Flemish pneumologists since 1990. Most categories of the classification by Crystal et al. (1) were incl uded 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 23 7 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 pneumo nitis 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%, ant hracosilicosis being excluded), histiocytosis X (3%), drugs (3%), angi itis and granulomatosis (2%), pulmonary hemosiderosis (1%), lymphocyti c infiltrative lung disease (1%) and lymphangioleiomyomatosis (1%). Th e order of relative frequencies of the different categories of disease s was the same in the 3 registration years. In 9% of the patients the diagnosis was confined to ''undefined fibrosis''. The diagnosis was co nfirmed by histology in 63% of the cases. The overall male-female rati o was nearly one, with, however, a male preponderance in hypersensitiv ity pneumonitis (22/12), UIP(8/3) and ''undefined fibrosis'' (14/7). A ll age groups were represented but 65% of the patients were over 50 ye ars old. Analysis of the postal codes showed following regional distri bution (for the whole study period): 51 patients lived in Flemish Brab ant, 111 in Antwerp, 31 in Limburg, 24 in East-Flanders, and 13 in Wes t-Flanders. Although this registration undoubtedly underestimates the real prevalence of interstitial lung diseases and may contain some bia s 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.