The discriminatory value of the P(A-a)O2 during exercise in the detection of asbestosis in asbestos exposed workers

Asbestosis is commonly associated with abnormalities of gas transport but since most asbestos workers are smokers and smokers also commonly have abnormalities in P(A-a)O2, the actual specificity and sensitivity of the P(A-a)O2 has been unknown. The P(A-a)O2 was measured at rest and exercise in 92 asbestos-exposed patients. These patients were divided into five groups based on their x-ray and pulmonary function status; normal, CAO, CAO and pleural disease, pleural disease alone and asbestosis with or without CAO. The P(A-a)O2/VO2(mm Hg)/L of O2 was the most discriminatory measurement of gas transport between groups, with mean values of 14.45 +/- 9.24 for normal, 19.04 +/- 10.52 for CAO, 16.85 +/- 8.94 for CAO and pleural disease and 34.07 +/- 21.54 for asbestosis with or without CAO. The P(A-a)O2/VO2 was of high specificity if greater than 35 mm Hg/L of O2 with only two out of 65 patients without asbestosis being considered abnormal. It was of low sensitivity in that only nine out of 27 patients with asbestosis would be detected if this were the sole criterion for diagnosis.