Platelet count in acute pulmonary embolism: its relationship to recurrences.

We have prospectively studied a large series of patients with acute venous thromboembolism, trying to correlate pulmonary embolism (PE) recurrences to a number of clinical variables, and platelet count behavior. A baseline lung scan was obtained initially in every patient. Repeated chest X-ray and lung scans were obtained routinely 8 days after heparin onset. The primary trial endpoint was confirmed, clinically apparent recurrent PE; in addition, laboratory evidence of subclinical PE at the repeat scan was also considered. PE recurrences were found in 26/180 patients, and 3 out of these patients died because of massive, recurrent PE. No significant differences were found in age and sex distribution, or in the degree of deep vein thrombosis proximity between patients who did or did not develop recurrences. There were, however, differences between groups in platelet count: No differences were found in baseline counts, but mean values were significantly lower by the 8th day when recurrences had appeared (229 +/- 86 x 10(9) liters-1 versus 314 +/- 129 x 10(9) liters-1; p < 0.005). The sensitivity, specificity, positive predictive value and negative predictive value for platelet count decrease were 52, 71, 21 and 91%, respectively. Thus, platelet count cannot be reliably used for individual cases, but our findings add to the pathophysiological picture of the disease.