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plasma (PT ratio) and International Normalised Ratio. (INR), activated partial thromboplastin time (aPTT) and ratio and platelet count. An increased aPTT ratio is.
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O਒ਉਇਉ਎ਁ਌ A਒ਔਉਃ਌ਅ Clinical relevance of isolated prolongation of the activated partial thromboplastin time in a cohort of adults undergoing surgical procedures Giuseppe Tagariello1, Paolo Radossi1, Roberta Salviato1, Milena Zardo2, Lucia De Valentin2, Marco Basso1, Giancarlo Castaman3 Transfusion Service, Haemophilia Centre and Haematology, 2Laboratory Analysis, Castelfranco Veneto Hospital, Castelfranco Veneto; 3Centre for Bleeding Disorders, Careggi University Hospital, Florence, Italy 1

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Background. Coagulation screening prior to surgery is performed routinely worldwide to identify patients at risk of bleeding during the procedure. Evidence from medical and surgical literature suggests that the activated partial thromboplastin time (aPTT) alone is suitable for predicting individual bleeding risk during surgery and it is current practice in our hospital to measure this parameter. Materials and methods. We retrospectively reviewed aPTT ratio results in 8,069 consecutive adult subjects undergoing elective surgery from January 1 to December 31, 2014 to confirm the validity of this approach. Results. In 7,606 patients (94.2%) the aPTT ratio was within the normal range while it was abnormal in 463 (5.8%). Out of these 463, 223 aPTT ratios were between 1.2 and 1.3 and we considered these results not worthy enough of further investigations. In 240 patients the aPTT ratio was higher than 1.3; in the vast majority of these cases (201/240; 83%) this abnormality was associated with oral anticoagulant treatment. Seventeen of the other 39 cases underwent detailed investigations which revealed lupus anticoagulant (n=7), decompensated chronic liver disease (n=4), factor XII deficiency (n=3), mild combined reduction of FXI and FXII (n=1) and mild haemophilia A (n=2). The other 22 patients underwent successful surgery without further investigation. Discussion. Our results from a pre-surgical setting seem to confirm the low prevalence of coagulation defects in the general population. Increased aPTT ratios were mainly attributable to oral anticoagulant therapy, with a few cases caused by mild, clinically irrelevant clotting factor deficiencies. A carefully taken personal history, including medications (i.e. oral anticoagulants) and/or previous bleeding symptoms seem more useful than coagulation screening tests to predict the risk of bleeding. Keywords: aPTT, aPTT ratio, pre-operative coagulation screening, surgery, elective surgery.

Introduction

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Coagulation screening tests are usually done preoperatively to determine the individual bleeding risk during surgery, but the real utility of this approach has been and continues to be a matter of debate1-5. The test panel includes prothrombin time as a ratio to normal plasma (PT ratio) and International Normalised Ratio (INR), activated partial thromboplastin time (aPTT) and ratio and platelet count. An increased aPTT ratio is quite common in clinical practice, but is not necessarily associated with a bleeding tendency6. Nevertheless, in daily practice detection of this abnormality may delay surgery and may be associated with increased costs because of re-testing and coagulation factor assessment as well as emotional stress for patients and their families. The "classical" splitting of the clotting cascade into intrinsic, extrinsic and common pathways has little in vivo validity, but represents a useful conceptual

categorisation for interpreting the results of laboratory investigations. Under this view the aPTT is considered a "global" coagulation test able to indicate abnormalities or deficiencies of the intrinsic and common pathways7. In 1995, in a prospective, multicentre study in the setting of routine pre-operative haemostatic screening, Houry et al.8 combined the results of standard tests, the patients' history and clinical data and divided 3,242 patients into four groups: group A had no clinical or coagulation abnormalities; group B had n