Farmer's lung precipitins in Doubs (a department of France): prevalence and diagnostic value.

In a French region where farmer's lung (FL) is common, we determined the prevalence of FL precipitins in dairy farmers and analyzed the relation between the presence of FL precipitins and the clinical probability of the disease. All the exposed dairy farmers of both sexes (n = 2555) from five districts of the Doubs department were asked to respond to a medical and professional questionnaire. A total of 1763 (69%) farmers agreed to participate. Precipitins tests were conducted in 551 (31%) farmers who showed any respiratory symptom and in a random sample of 100 asymptomatic farmers. Serum for each farmer was analyzed by both double diffusion and immunoelectrophoresis against Micropolyspora faeni (MF) and extracts of moldy hay (HE) from Doubs. The 651 farmers were then divided into four groups (G 1-4) with a decreasing probability of FL (G1: typical FL symptoms; G4: asymptomatic farmers). The estimated prevalence of precipitins in the whole population was as follows: 1) by double diffusion, against HE: 83%, against MF: 27%; 2) by immunoelectrophoresis, against HE: 26%, against MF: 19%. There was a close "linear" relation between the prevalence of precipitins detected by immunoelectrophoresis against HE and the symptoms: 51% in G1, 36% in G2, 29% in G3, and 13% in G4. Precipitins detected by immunoelectrophoresis were also related to exposure and geography (more immunization in tableland area than in plain or mountain area). Presence of precipitins detected by double diffusion was not related to symptoms, exposure, or geography.(ABSTRACT TRUNCATED AT 250 WORDS)