Chest
Volume 87, Issue 2, February 1985, Pages 202-205
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Usefulness of Skin Test in Farmer's Lung

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The skin test with hay extract or with Micropolyspora faeni (MF), is not commonly used in the diagnosis of Farmer's lung (FL), as it is not considered specific. In our study, we have applied the intracutaneous test with these antigens in 26 patients affected with FL; 18 of them were still in contact with the antigen and the remaining eight had not been in contact with the hay during the previous year. Twenty-five asymptomatic farmers (AF) served as a control group. In the first group and with hay extract, the immediate reading (I) was positive in 15 of 18 (83.3 percent), the late reaction (L) in 18 of 18 (100 percent), and the delayed one (D) in eight of 18 (44.4 percent). In the 25 AF, the results were as follows: I, seven of 85 (28 percent); L, 17 of 25 (68 percent); and D, one of 25 (4 percent). Consequently, the differences between both groups were significant: I, p<0.01; L, p<0.05; and D, p<0.01. Using MF as an antigen, the test is somewhat less effective: p<0.02, p<0.02, and p<0.2, respectively. These results suggest that the intradermal injection with hay extract is an easy, effective test in the diagnosis of FL, and at the same time, a better means of distinguishing FL patients from AF than the precipitation test.

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MATERIAL AND METHODS

The study included 26 patients with FL, the diagnosis of which was based on the presence of clinical, roentgenologic and immunologic characteristics. All subjects had histories of dyspnea after exertion and had suffered at least one episode of dyspnea a few hours after contact with mouldy material. Functional respiratory tests (spirography, lung volumes, and diffusing capacity for carbon monoxide) showed a restrictive pattern in 25 patients and obstruction in ten of the 25. The diffusion

Skin Test with MH

In the 18 patients with FL with recent antigenic contact, the immediate readings (I) were positive in 83.3 percent (15 of 18); the late reaction (L) in 100 percent (18 of 18); and the delayed reaction (D) in 44.4 percent (eight of 18).

In the 25 AF, the results were: I, 28 percent (seven of 25); L, 68 percent (17 of 25); and D, 4 percent (one of 25). Therefore, as we have set out in Table 3, the difference is significant: p<0.01 for reading I, p<0.05 for the L reaction, and p<0.01 for the D

DISCUSSION

In bird breeders disease, the diagnostic usefulness of the skin test has been shown.7, 8, 9, 10, 11, 12 In farmers lung, another form of extrinsic allergic alveolitis, although some experimental studies 13,26 have been carried out in animals which became ill after inhaling hay, showing positive skin reactions, the clinical usefulness of this test in general is not accepted.11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 The nonspecificity of the skin test in this disease has often been

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  • Cited by (0)

    Manuscript received February 13; revision accepted August 10.

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