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Routine Laboratory Screening for Bleeding Risk

It is well established that a detailed clinical history is the most important first step in determining a patient’s bleeding risk and the need for coagulation testing. This should include inquiry about excessive bruising, nosebleeds, menorrhagia or other bleeding tendency, excessive bleeding after dental extraction, surgery or childbirth, a family history of a bleeding disorder, presence of liver, renal or hematological disease, and use of medications or herbal supplements that may interfere with hemostasis. 

Common laboratory screening tests for hemostasis include APTT, PT, and platelet count. The routine use of these tests to predict bleeding in unselected populations is expensive, and there is evidence in the literature demonstrating that this approach is unwarranted. A recently published review addressed this issue (Ann Intern Med. 2003; 138:W15-W24). Data was extracted from published studies (between 1966 and 2002) of routine coagulation testing in non-surgical hospitalized patients, and surgical patients. In the surgical patients sensitivity and specificity of the APTT in predicting postoperative hemorrhage were calculated.

The authors conclude that patients hospitalized for non-surgical diagnoses do not benefit from routine admission testing of APTT or PT, in the absence of synthetic liver dysfunction or a history of oral anticoagulant therapy. Observational studies have failed to show improvement in clinical outcomes with the use of these tests. Routine admission testing increases costs and the likelihood of false positive results. Two retrospective studies showed that the routine use of these tests has little or no impact on clinical care.

Routine platelet counts in asymptomatic non-surgical patients are also costly and not generally indicated. Monitoring platelet counts is indicated during heparin therapy because of the importance of detecting heparin-induced thrombocytopenia.

In surgical patients, the likelihood of detecting a significant hereditary coagulation factor deficiency in an unselected asymptomatic population is very small (17 per 100,000 in men and 5 per 100,000 in women). Furthermore, the probability of postoperative hemorrhage is exceedingly low (0.22%) among patients considered low-risk for hemorrhage (based on clinical history and examination). In a study of more than 2000 patients who had preoperative coagulation testing, the APTT had a sensitivity of 33% and a specificity of 84% in predicting postoperative hemorrhage. The likelihood ratio (true positive rate/false positive rate) of the APTT in predicting postoperative bleeding among low-risk patients was less than 1.0, indicating that the test provided no useful information. Even in patients considered high–risk for postoperative hemorrhage the APTT was of limited value in predicting hemorrhage because of low sensitivity and specificity (59% and 68% respectively). In the high-risk group the likelihood ratio of hemorrhage was 1.8, however confidence limits were wide. Several other clinical studies confirmed that preoperative coagulation studies should not be used as a screening test in asymptomatic patients. Such testing does not reliably predict increased or decreased risk for hemorrhage, may be misleading, and may lead to further unnecessary testing.

The authors make the following recommendations regarding the use of screening coagulation tests:

Non-surgical hospitalized patients

  • Testing (APTT, PT, platelet count) should be performed only when there are specific clinical indications based on history or physical examination.
  • Platelet count monitoring is indicated before and during heparin therapy.

Surgical patients

  • Routine preoperative coagulation testing is not recommended.
  • Preoperative testing (APTT, PT, platelet count) is warranted for patients with clinical evidence on history or physical examination to suggest a bleeding disorder.

If a platelet function defect is suspected (e.g. use of platelet-inhibitory drugs) a platelet function screening assay (PFA-100) is suggested.

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