Prothrombine time (PT) and activated prothrombine time (aPTT) are common tests used for screening of coagulation function before surgical procedures. We analyzed underlying causes of abnormal coagulation test results which were incidentally found during pre-surgical evaluation in healthy patients without definite bleeding history. Total 58 children referred to pediatric hematoloy service for abnormal PT and aPTT results in pre-surgical evaluation between June 2006 and May 2008 were analyzed retrospectively by review of medical records. 50 patients showed aPTT prolongation, 5 patients PT prolongation, 2 patients PT and aPTT prolongation and another three patients showed normal PT and aPTT. Among 55 patients with abnormal results, 25 patients (43%) were recovered spontaneously during their follow up tests, 17 patients (29%) showed lower level of certain coagulation factor than reference range and the other 13 patients were lost during follow up despite of recommendation for further evaluation. Mean value of international normalized ratio (INR) for PT and aPTT of the patients recovered spontaneously were 1.05±0.11, 44.53±5.01seconds(s), and 1.12±0.11, 47.0±5.36s in patients with lower level of coagulation factor, showing significant increase of PTT in patients with lower factor levels (p<0.05). Median time required for spontaneous recovery was four weeks and 18 patients (72%) were recovered within this time. Among 17 patients with lower level of certain coagulation factor then reference level, there were 11 patients with low factor XII level, three patients with low factor VIII level, three patients with low von Willebrand factor, two patients each for low factor VII and factor XI and one patient with low factor V level. Among them three patients with low level in von Willebrand factor, one patient with low factor VII and two patients with low factor XI showed deficient level of coagulation factors requiring factor replacement for the surgical procedures. From this analysis of patients with incidentally found PT or aPTT prolongation, 43% of patients were spontaneously recovered during follow up period within 4 weeks in median. However, we also found that 29% of patients had relatively lower level of coagulation factor than reference range. Even though most of them were factor XII decrease which is not closely related with bleeding tendency, six patients had significant deficiencies of coagulation factors requiring factor replacement during surgical procedures. These results suggest that we should keep following up and undergo adequate evaluation for underlying coagulation factor deficiencies in patients who have sustaining PT and aPTT prolongation abnormalities despite of absence of any bleeding history.

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