Two Serum Markers of Collagen Biosynthesis as Possible Indicators of Irreversible Pulmonary Impairment in Farmer’s Lung1–3

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Abstract
Serum galactosylhydroxylysyl glucosyltransferase activity (S-GGT) and serum procollagen type III aminoterminal propeptide concentration (S-PRO(III)-N-P) were measured in 40 patients with farmer’s lung at the time of an acute attack of the disease and 6 months later in order to study the usefulness of these serum markers for predicting the development of interstitial lung fibrosis. These 2 serum parameters have previously been found to reflect tissue collagen synthesis, especially in fibrotic hepatic diseases. The mean S-GGT was significantly increased when compared with the reference mean both at the time of the acute attack (p < 0.001) and after 6 months (p < 0.001). Approximately half of the patients had a S-GGT value higher than the upper normal limit at the acute stage, after which the levels decreased significantly (p < 0.01). S-PRO(lll)-N-P remained at the control level in most patients at the acute stage of the disease, followed by a small but significant increase (p < 0.01), so that by the end of 6 months of follow-up one third of the patients had a S-PRO(lll)-N-P value slightly above the upper normal reference value. Double blind tests on the administration of corticosteroids to half of the patients suggested that corticosteroids might have some favorable effect on the disease, although no significant response was found. The patients with definitely abnormal pulmonary function tests 1 yr after the acute stage had significantly higher initial S-GGT values than the rest of the patients (p < 0.001). Elevated S-GGT at the acute stage was observed in 90% of the patients with definitely abnormal lung function after 1 yr but in only 30% of the other patients. S-GGT at the acute stage had a significant negative correlation with pulmonary diffusing capacity measured 6 months (p < 0.05) and 1 yr (p < 0.01) after the acute attack. The patients with abnormal S-GGT at the acute stage had a slower and less complete recovery from the disease, as judged by the improvement in lung function tests than those with normal initial S-GGT. In conclusion, a high S-GGT value at the acute stage of farmer’s lung may indicate the development of interstitial pulmonary fibrosis, and S-GGT determinations may, therefore, be used to predict the extent of long-term respiratory impairment in these patients.