Exam 45: Laboratory Evaluation of Hemostasis

A 53-year-old woman arrives at the hospital with bleeding into the back of the throat and has a coagulation screen performed. She has no history of abnormal bleeding before this despite major stress to hemostasis in the past: she was in a major automobile accident at age 37 and has had impacted wisdom teeth extracted. Her coagulation results follow: Which of the following is the most likely cause for her bleeding?

How often must the partial thromboplastin time (PTT) reference interval be determined?

A patient's platelet count drops 4 days after being placed on heparin. Select the correct interpretation.

A platelet aggregation study shows diminished response to all agonists except for a small response to arachidonic acid and full response to ristocetin. Which condition is most likely?

Patients with which of the following would have a normal PT?

Which of the following is acceptable practice regarding collection of blood when using a syringe and winged needle set?

A patient sample has normal platelet aggregation patterns for all agonists except that no reaction occurs with ristocetin. Ristocetin agglutination is not corrected with exogenous VWF. What condition is most likely?

A patient is stabilized on warfarin with an international normalized ratio (INR) of 2.7. He develops pneumonia and is admitted to the hospital. His appetite is depressed and he is placed on broad-spectrum antibiotic agents. At 1 week after the admission, his INR is 5.0. What is the most likely interpretation?

Which of the following is an acceptable sample for a prothrombin time (PT) test?

Standard curves are necessary for which coagulation procedures?

The urea solubility test evaluates factor:

A patient admitted to the hospital with thrombosis is given the standard heparin dosage. Twenty-four hours after the heparin is started, the PTT is 38 seconds (reference range, 25 to 37 seconds). Both normal and abnormal controls are within their limits. Which of the following is most likely?

Which of the following will cause spuriously prolonged clot-based coagulation tests?

A patient is positive for fibrin degradation products and negative for D dimers. Which condition is most likely?

Which of the following conditions is associated with an elevated fibrinogen?

Which of the following conditions would have a normal PTT?

A prolonged PTT is corrected when mixed with normal plasma and tested immediately and after a 2-hour incubation. Which test (or tests) should be performed next?

Which of the following is necessary for normal platelet aggregation?

How often must controls be run for the PT and PTT?

A patient has a hematocrit of 65%. Which of the following is true related to coagulation testing?