Abstract

Unfractionated heparin (UFH) is the most widely used anticoagulant in hospitalized patients. The therapeutic range (TR) was defined in adults according to the prolongation of the activated Partial Thromboplastin Time (aPTT). However, the recommendation is to maintain a therapeutic range with anti-factor Xa assay (antiFXa). As this technique is more complex to perform and less available, it is recommended to make local correlation curves of aPTT with antiFXa. Objective: to determine the correlation between the values of aPTT and antiFXa in patients treated with UFH. Patients and Method: 52 patients between 2 days to 14 years of age hospitalized in the Pediatric Critical Patient Unit were recruited. They received treatment with UFH in continuous infusion for at least 24 hours. aPTT and antiFXa tests were performed according to the moment of anticoagulation. To evaluate the concordance of the levels of aPTT with those of antiFXa, the Kappa statistical coefficient of Landis and Koch was used. Results: 105 samples were collected from 52 patients. The overall concordance was 0.452 (moderate correlation). In patients aged < 1 month (n = 40), a considerable correlation was evident (r = 0.617); in those from 1 month to < 6 months (n = 18) and 6 months -< 12 months with aPTT < 120 seconds (n = 11), also showed a considerable correlation (r = 0.636 and 0.615, respec-tively), while in those aged > 12 months (n = 37) with aPTT < 120 seconds, a moderate correlation was evident (r = 0.454). Conclusion: In our population, there is a moderate correlation between the values of aPTT and antiFXa.