STRATEGY THAT INCLUDES SERIAL NONINVASIVE LEG TESTS FOR DIAGNOSIS OF THROMBOEMBOLIC DISEASE IN PATIENTS WITH SUSPECTED ACUTE PULMONARY-EMBOLISM BASED ON DATA FROM PIOPED

Objective: To estimate the percentage of patients with suspected acute pulmonary embolism in whom a noninvasive diagnosis or exclusion of th romboembolic disease might be safely made on the basis of ventilation- perfusion (VQ) lung scans, single noninvasive tests of the lower extre mities, and, in patients with adequate cardiorespiratory reserve, seri al noninvasive tests of the lower extremities. Methods: Calculations w ere made among 662 patients who participated in the collaborative stud y Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) a nd who had blood gas values measured while breathing room air and who underwent pulmonary angiography. The diagnostic strategy recommends tr eatment in all patients with a high-probability VQ scan and no treatme nt in patients with nearly normal VQ scans. Inpatients with nondiagnos tic VQ scans (intermediate- or low-probability scans), a single noninv asive leg testis recommended. It was assumed that 50% of patients with pulmonary embolism would show deep venous thrombosis with a single no ninvasive leg test. If results are abnormal, treatment is indicated. I f normal, serial noninvasive leg tests are recommended. Treatment can be withheld if results of serial tests are normal. In patients with po or cardiorespiratory reserve, pulmonary angiography is indicated. Resu lts: A single noninvasive leg test in patients with nondiagnostic VQ s cans would show deep venous thrombosis and, therefore, eliminate the n eed for pulmonary angiography in 53 (11%) of 468 patients (95% confide nce interval [CI], 9% to 15%) who otherwise would require angiography. Serial noninvasive leg tests in patients with adequate cardiorespirat ory reserve who had a normal result of a single leg test would either show deep venous thrombosis or exclude it in 222 (47%) of 468 patients (95% CI, 43% to 52%). The need for pulmonary angiography, therefore, would be reduced from 468 (71%) of 662 (95% CI, 67% to 74%) if no noni nvasive leg tests were performed to 415 (63%) of 662 (95% CI, 59% to 6 6%) if only a single noninvasive leg test were performed, and further reduced to 193 (29%) of 662 (95% CI, 26% to 33%) if serial noninvasive leg tests were used where appropriate. Conclusion: A noninvasive stra tegy that includes VQ scans, single noninvasive leg tests, and serial noninvasive leg tests would permit a diagnosis of thromboembolic disea se or a safe exclusion of thromboembolic disease in 71% of patients wi th suspected acute pulmonary embolism.