Cause Analysis Of Abnormal Coagulation Screening Tests Of Inpatients In Peking Union Medical College Hospital

Background and objectives:Prothrombin time (PT), activated partial thromboplastin time(APTT), thrombin time(TT)and fibrinogen(Fbg) level are the most common coagulation tests. Their common uses include anticoagulation monitoring, bleeding tendency assessment and routine preoperative coagulation screening. Besides receiving anticoagulant therapy, when coagulation test results appear abnormal in patients without known causes like receiving anticoagulant therapy, further investigation should be needed to identify possible congenital or acquired bleeding disorders. Most patients in our hospital have received these tests. However, the proportion of abnormal results hasn’ t been systematically calculated. Besides, the underlying causes and bleeding risk of patients with borderline results haven’t been thoroughly studied.Researches focus on these matters will help us to understand the incidience of abnormal coagulation test results in our hospital.Methods:Information about all the routine coagulation test results in Peking Union Medical College Hospital between January15th,2013and March14th,2013was collected. The number, incidence and department distrubution of abnormal results (abnormal is defined as PT, APTT or TT prolongation or Fbg decrease in this study) were calculated. The clinical data and plasma samples were collected. For those with obvious causes, the incidence of each cause was caculated. For those with unknown etiology, an initial50:50correction with normal pooled plasma was done and a standard panel of tests including measurement of coagulant factor acitivity, von Willebrand factor antigen (vWF:Ag) levels and detection of lupus anticoagulant or other specific factor inhibitors was performed.Results:1.3596requests were performed within these two months, of which1304turned out to be abnormal. The Intensive Care Unit had the largest proportion in all the abnormal results.2. Among all the abnormal conditions, APTT and PT prolongation made up the largest part.3.701cases had APTT or/and PT prolongation, in which319had known causes, mainly anticoagulant therapy and chronic liver disease. Among the rest382cases, the causes were unknown.4. FXII deficiency was the most common cause of isolated APTT prolongation, accounting for36.1%of this group.5. Combined vitamin K-dependent coagulation factor deficiency was the most common cause of isolated PT prolongation, accounting for23.0%of this group.6. Cases with unknown etiology was the most common cause of combined APTT and PT prolongation, accounting for49.0%of this group and couldn’t be corrected by mixing study. The second common cause was lupus anticoagulant(34.0%).7. The median APTT for weak lupus anticoagulant is38.2s (ranging from32.3s to56.4s),34.5s for the moderate lupus anticoagulant (ranging from32.4s to41.3s). There was no obvious correlation between the degree of APTT prolongation and the strength of lupus anticoagulant positivity.Conclusions:1. APTT or/and PT prolongation is the most common group of all the abnormal results in Peking Union Medical College Hospital.2. The most common cause for isolated APTT prolongation is FXII deficiecy in our study. Thus FFP is not indicated for most patients with this abnormal result.3. The most common cause for isolated PT prolongation is combined vitamin K-dependent coagulation factor deficiency. Thus we recommend vitamin K supplementary therapy for patients with isolated PT prolongation who are at high risk of vitamin K deficiency.4. Clinicians should be aware of the possibility that even the APTT or PT prolongation is within the borderline range, patients may still have bleeding risk.5. There is no obvious correlation between APTT prolongation and the strength of lupus anticoagulant positivity.6. Lupus anticoagulant could exist in samples that can be corrected by normal pooled plasma.7. Preanalytical error is an important cause of abnormal coagulation results and should be avoided.