The diagnosis of acute flbrinous pericarditis using 125 I labelled fibrinogen

Twenty-seven patients, five with clinical pericarditis and 22 without, were studied using an 125 I fibrinogen technique in which the ratio of praecordial to direct blood counting was compared from day to day. There was a rise in the praecordial to blood-count ratio in all cases of clinical pericarditis. This technique may prove of value in the diagnosis of suspected pericarditis. Intravenously injected 125 I fibrinogen is incorporated into the body pool of fibrinogen after a short period. It will therefore appear in any place where fibrin deposition occurs, for example in the veins affected by active venous thrombosis. The increase in radioactivity at these sites can be detected by external counting with a scintillation counter and this technique has been used successfully in the diagnosis of venous thrombosis and renal transplant rejection (Negus et ah, 1968; Salaman, 1970). During an attack of acute fibrinous pericarditis, fibrin is deposited between the two layers of the pericardial sac. It therefore seemed possible that labelled fibrinogen given before or during the acute illness would be taken up in this region and lead to an increase in 125 I activity over the praecordium. Using a portable scintillation counter it should be possible to detect this increase by comparing the ratio between the praecordial and blood counts measured at daily intervals. To test this hypothesis 27 patients who were already receiving 125 I fibrinogen as a screening test for the presence of calf vein thrombus were studied. MATERIALS AND METHODS