DETERMINATION OF SEVERE IMPAIRMENT (DISABILITY) IN INTERSTITIAL LUNG-DISEASE

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Abstract
Physicians trained primarily to recognize and treat disease are being asked more frequently to quantify impairment of health. Criteria for defining impairment due to chronic obstructive pulmonary diseases are widely accepted, but it was difficult to establish guidelines for interstitial diseases. To develop and validate criteria, 2420 patients with airflow obstruction were selected; 821 had interstitial disease and 938 were employees of asbestos industries. Clinical and roentgenographic criteria were inappropriate for defining impairment. The forced vital capacity and single breath diffusing capacity, each expressed as a percentage of the predicted value, were selected for analysis. Sensitivity studies using response to standard exercise as an independent criterion suggested that the limits reflecting severe impairment were a forced vital capacity 50% of predicted and a single breath diffusing capacity 40% of predicted. Applying these criteria, 35.6% of patients with interstitial pneumonia, 12.1% with sarcoidosis, 13.6% with pneumoconioses and 1.1% of the workers exposed to asbestos were severely impaired. In more than 1/2 of patients the single breath diffusing capacity was the only test that indicated severe impairment.