[Checking oral anticoagulation in capillary blood]

To check out the reproducibility and costs of prothrombin time (PT) determination as a control of oral anticoagulant therapy (OAT) in plasma and capillary blood.

The study was carried out in two phases: along two years, 1,700 patients with OAT were controlled, 700 of them in the hospital outpatient clinic. In 149 patients INR was simultaneously determined in both capillary and venous blood. The 700 patients receiving acenocoumarin who had been controlled in 1991 according to the conventional plasma-sample fashion, were controlled in the second year (i.e., 1992) by means of capillary blood testing, a comparison of the costs of each method and the need for anticoagulant drugs being undertaken. Venous blood PT was assessed with reagent thromboplastin (Tromborel S) in an Electra-1000 (MLA) system. An automated Trombotrack system was used for the capillary blood tests using Thrombotest as current procedure. The results were expressed as INR in both methods. The statistical evaluation of the results was carried out by means of Student's t, variance analysis, and correlation study.

No significant differences were found in the anticoagulation intervals attained from venous or capillary blood samples. No significant differences were seen in 87 patients on whom the test was repeated in two samples drawn from a single capillary puncture. The weekly OAT doses of 30 patients along six months were analysed. The need for anticoagulant drugs was similar (17.4 vs 17.2 mg/patient/week). The mean INR in 1991 was 2.82 and the mean drug-need was 15.24 mg/week, whereas in 1992 the mean INR was 2.86 and the need for anticoagulant was 15.49 mg/week. The costs of the conventional method were 103.6 Pta, this being 70 Pta for capillary blood, which means a 32% savings.

OAT control by means of PT performed on capillary blood must be considered a substitutive method for the venous blood assay due to its efficacy, simplicity and lower costs.