Hemostasis- Lab Determinations
All of the following substances can be used to induce platelet aggregation when performing platelet aggregation studies EXCEPT:
Plasminogen
A point-of-care test used to evaluate bleeding problems and monitor antiplatelet medication is called?
Platelet function assay (PFA)
A patient has a history of repeated spontaneous abortion. Coagulation studies reveal an elevated APTT, normal PT, normal platelet function, and normal thrombin time. Schistocytes were seen on the peripheral blood smear. Which test should be performed to determine if the patient has lupus anticoagulant?
Platelet neutralization test
Which of the following laboratory tests of hemostatic function is a screening test used to assess the functionality of both the intrinsic and common pathways?
Activated partial thromboplastin time (aPTT)
Which of the following tests is used to monitor therapy with unfractionated heparin?
Activated partial thromboplastin time (aPTT)
All of the following are likely the causes of an abnormal thrombin time (TT) EXCEPT:
Aspirin
Which tests will be abnormal in a patient with Fibrin Stabilizing factor deficiency?
Both 5 M urea clot solubility test and Factor XIII assay
Which of the following coagulation test results would be prolonged in deficiency of Factor X?
Both PT and aPTT
A deficiency in which of the following coagulation factors will produce an abnormal prothrombin time (PT) test result, but will not affect the activated partial thromboplastin time (APTT) test result?
Factor VII
A patient has a prolonged non-therapeutic PT and a normal aPTT. The physician orders a PT mixing study. The results are as follows: Original PT test- 32 seconds 1:1 Mix (room temp immediate) - 22 seconds 1:1 Mix (incubated for 90 minutes) - 23 seconds Which factor may be present in abnormally low levels and causing the prolongation?
Factor VII
Which of the following factors does not affect the result of the aPTT assay?
Factor VII
Which of the following conditions can produce a normal aPTT and a prolonged PT?
Factor VII deficiency
Dysfibrinogenemia can be caused by many different structural mutations of the fibrinogen genes, and can result in bleeding, thrombosis, or in some patients, no symptoms. A lab test which differentiates dysfibrinogenemia from afibrinogenemia is:
Fibrinogen antigen assay
The D-dimer is useful in detecting activity in which aspect of hemostasis?
Fibrinolysis
Which test result will be normal in a patient with dysfibrinogenemia?
Immunologic fibrinogen level
What may prevent the detection of lupus anticoagulant in a plasma sample if the blood used for testing is not centrifuged for a sufficient time?
Increased platelets in the plasma sample
A variety of additives are used in blood collection tubes. Which of the following additives prevents clotting by inhibiting thrombin and thromboplastin?
Lithium or sodium heparin
To determine if an elevated aPTT is caused by a factor deficiency or a factor inhibitor when the PT is normal, the FIRST step would be:
Mix one part patient plasma and one part normal pooled plasma and repeat the aPTT
After several incidences of deep vein thrombosis (DVT), a patient is to be assessed for hypercoagulability. The following would be an appropriate panel for hypercoagulability screening:
PT, aPTT. Lupus Anticoagulamt (LA) screening, Activated Protein C resistance (APC) , d-dimer screening
Which laboratory result is the most critical in recognizing heparin-induced thrombocytopenia (HIT)?
Platelet count
Which potent inhibitor of platelet aggregation is released by endothelial cells?
Prostacyclin
A test used to evaluate the abnormalities in the intrinsic coagulation pathway and to monitor heparin therapy is called:
Prothrombin time (PT)
To obtain accurate aPTT times in patients who have hemophilia and have blood drawn from implanted venous access devices, it is important to:
Treat patient plasma with heparin neutralizers and then do the aPTT
Which of the following blood collection tubes is appropriate for coagulation testing?
bLUE
After the physician orders a follow up for abnormal coagulation screening tests, the laboratorian completes a mixing study with the following results: Initial aPTT result: 98 seconds Initial 1:1 Mix with Normal Pooled Plasma: 28 seconds Incubated 1:1 Mix with Normal Pooled Plasma: 30 seconds Which of the choices below would most likely explain the results for this patient?
Factor VIII deficiency
All of the following disorders would affect the results of a Prothrombin time (PT) EXCEPT?
Factor VIII deficiency
The dissolution of a clot with 5M urea indicates which one of the following factor deficiencies?
Factor XIII
A patient's coagulation mixing study results are shown below after an initially prolonged aPTT result. Initial aPTT Immediate aPTT mixing study Incubated aPTT mixing study 63 sec. (normal range 21-34 seconds) 26 sec. 65 sec. Has the aPTT been corrected by the mix? Is a factor deficiency or a coagulation inhibitor the more likely cause of the patient's prolonged aPTT?
Not Corrected, Coagulation Inhibitor
Which of the following is a quantitative test which is commonly available to determine Protein C and Protein S antigen levels?
Enzyme immunoassay
The prothrombin time test will detect deficiencies in which pathways?
Extrinsic and common pathways
An increased D-Dimer can be associated with all of the following EXCEPT:
Factor Deficiency
Which one of the following factors, if deficient, would cause a prolongation of the PT assay without prolonging the aPTT?
Factor VII
Which of the following laboratory results would you find with disseminated intravascular coagulation (DIC) but NOT with thrombotic thrombocytopenic purpura (TTP) or hemolytic uremic syndrome (HUS)?
Prolonged PT and aPTT
A specimen drawn from an indwelling catheter that was contaminated by heparin would be indicated by:
Prolonged aPTT and normal reptilase time test
Which of the following laboratory tests is commonly used to monitor oral anticoagulant therapy?
Prothrombin time (PT)/INR
You have just performed stat PT and aPTT tests on your coagulation instrument. Your results are as follows: PT = 12 seconds (normal range 10-13 seconds) aPTT = 24 seconds (normal range 21-34 seconds) What would be your next step?
Report the results.
Which one of these test systems can be used to evaluate the adequacy of fibrinogen in heparinized patients?
Reptilase Time
Ristocetin is used in certain von Willebrand Factor (vWF) functional assays. The reason it is used is because:
Ristocetin enhances binding of vWF to platelet GPIba
What is the ratio of patient plasma to pooled normal plasma (PNP) that is usually used in the performance of a mixing study?
1:1
What is the CORRECT blood-to-anticoagulant ratio in blue top (sodium citrate) tubes used for coagulation tests?
9:1
A laboratory professional is going to perform a mixing study to differentiate between a factor deficiency and a coagulation inhibitor as the cause of a prolonged prothrombin time (PT) or activated partial thromboplastin time (aPTT) test result. The mixing study should be performed within what time frame following collection of the specimen?
4 hours
Traditional coagulation assays are based almost solely on this technique:
Clot-based assays
All of the following tests are useful in the diagnosis of heparin induced thrombocytopenia (HIT) EXCEPT:
Dilute partial thromboplastin time (DTT)
When performing controls for the morning run in coagulation, the normal control is within acceptable limits for both the PT and APTT, but the abnormal control is out of range for both procedures. Which of the following would be an appropriate action to take?
Document QC, repeat the abnormal control, troubleshoot if necessary; report patient results only when both controls are within acceptable ranges
What is the correct procedure when using a winged collection device (butterfly) to draw a light-blue top tube intended for a coagulation test if this is the first tube that will be collected in the draw?
Draw and discard a waste light-blue top tube before the tube that will be used for coagulation studies.
What are the expected lab results in the condition known as "Afibrinogenemia"?
Elevated PT, elevated aPTT, elevated thrombin time (TT) and elevated reptilase time
What is the anticoagulant most commonly used for routine coagulation testing?
Sodium citrate
Which one of the following anticoagulants is used most commonly for most coagulation studies?
Sodium citrate
What is the International Normalized Ratio (INR) calculation used for?
Standardize PT results between different reagent sensitivities
The ratio of whole blood to anticoagulant is very important in the PT assay; at which hematocrit level should the standard anticoagulant volume be adjusted?
> 55%
The following describes a clot-based test to assess Protein C function, as well as the results of someone's test who has a protein C deficiency.
A parital thromboplastin time (PTT) is performed using C-depleted normal plasma, a venom activator of protein C (such as Protac), and a heparin neutralizer. The clotting time would not be prolonged in someone with a protein C deficiency.
What may cause the following mixing studies results? Initial aPTT = 133 seconds 1:1 Mix aPTT pre-incubation = 33 seconds 1:1 Mix aPTT post-incubation = 124 seconds
A slow acting coagulation inhibitor
An abnormality of which of the following assays would be LEAST likely to be associated with thrombotic tendency?
APTT
Which of the following laboratory results is characteristic for a patient with Von Willebrand disease?
Abnormal platelet aggregation response to ristocetin
Which of the following is LEAST useful in differentiating hemophilia A from hemophilia B?
Activated Partial thromboplastin time (aPTT)
What are the PRIMARY reagents used in the activated partial thromboplastin time (aPTT)?
Activated partial thromboplastin and calcium
All of the following are coagulation assays that employ low-reagent phospholipids and thus are sensitive to Lupus Anticoagulant (LA) (Antiphospholipid Antibodies) EXCEPT:
Activated partial thromboplastin time (aPTT
In patients who have developed heparin-induced thrombocytopenia with thrombosis (HIT), which of the following should be used to prevent ischemic stroke?
Direct thrombin inhibitors
When monitoring the use of low-molecular-weight heparins becomes necessary, which of the following laboratory tests is recommended?
Anti-Xa
A laboratory test to determine heparin levels in a patient's plasma is:
Anti-factor Xa assay (anti-FXa)
Which of the following tests is used to quantify a coagulation inhibitor?
Bethesda assay
The INR (international normalized ratio) is calculated using the following formula:
INR=(PT patient / PT normal) raised to the ISI.
The laboratorian completed the mixing study ordered for John Doe. The results are as follows: Initial aPTT result: 167 seconds Initial 1:1 Mix with Normal Pooled Plasma: 158 seconds Incubated 1:1 Mix with Normal Pooled Plasma: 150 seconds Which of the choices below would most likely explain the results for this patient?
Immediate-acting coagulation inhibitor
What MINIMUM level of a particular factor will cause the aPTT test to become prolonged?
Less than 40%
A D-dimer test is collected in which color test tube?
Light blue
A patient initially has a prolonged PT. After reviewing the patient's case and laboratory findings, the physician administers intravenous vitamin K. The repeat PT results are normal after 24 hours of vitamin K therapy. What clinical condition is MOST likely to produce these results?
Liver disease
What would be a PROBABLE diagnosis for a habitual alcoholic with slight elevations in the PT and aPTT tests?
Liver disease
Abnormal thrombin times (TT) can be caused by all of the following EXCEPT:
Low platelet count
Which of the following tests could be used to determine whether an abnormal screening coagulation test result (PT or aPTT) is caused by a factor deficiency or an inhibitor?
Mixing studies
Anticoagulant drugs which are direct thrombin inhibitors (such as argatroban and bivalirudin) can prolong which of the following clot based assay/s?
PT, aPTT and Ecarin clotting time
Which of the following tests may be used to confirm screening test results for a lupus anticoagulant (or antiphospholipid antibody)?
Russell Viper Venom test
Von Willebrand Factor (vWF) multimer analyses of patient's plasma can be performed by:
SDS agarose gel electrophoresis
Consider the following set of results from a mixing study of a patient with a suspected coagulopathy. Initial aPTTImmed. aPTT mixing studyIncubated aPTT mixing study86 sec. (reference range 21-34 sec.)87 sec.88 sec What is the most likely cause of these results?
The assay did not correct, indicating a likely coagulation inhibitor.
Thromboelastography is a point of care test which measures which of the following?
The entire coagulation status of the patient
A prothrombin time (PT) specimen was collected at an outpatient clinic and will not be picked up by the testing laboratory's courier until several hours later. How should the specimen be stored until it is picked up by the courier?
The tube should remain unopened and be kept at room temperature (20°-25° C).
The clot-based assay that is most specific for measuring fibrinogen function is the:
Thrombin Time (TT)
This assay would be used to help rule-out heparin contamination in a coagulation sample:
Thrombin time
If a sodium citrate sample drawn for coagulation is noted to be filled an inch below the fill line (black line), then the specimen is considered:
Unacceptable for coagulation studies
The principle of most commercially available d-dimer assays is:
Using specific antisera to detect d-dimers' neo-epitopes
When performing your mixing study, you aliquot your sample plasma and the pooled normal plasma to create your "mix". You then place the sample in a water bath to incubate for 90 minutes before running your new mixed sample. What is the problem with the steps involved in the procedure above?
You have not run a PT or aPTT on the new mix before incubating.
A patient with a history of frequent mild bleeding episodes has the following results: Normal PTProlonged aPTT corrected by normal plasma during mixing studies Which of the following could be a possible cause of the initial aPTT prolongation?
Factor IX deficiency
Which of the following assays is commonly used to confirm the diagnosis of Activated Protein C resistance?
Factor V Leiden Mutation Assay
The most specific test to detect both presence of Factor V Leiden, also known as activated protein C resistance (APC) and predict risk of thrombosis is:
Factor V Mutation Assay
Which of the following conditions will show an increased prothrombin time (PT) with a normal activated thromboplastin time (aPTT)?
Factor VII deficiency
A newly admitted patient has the following coagulation results:PT: 12.9 seconds (N = 12-14 seconds)aPTT: 84 seconds (N = 25-35 seconds)Platelet Count: 200 x 109/L (N = 150-450 x 109/L) A mixing study was performed due to the abnormal aPTT test results. The mixing study demonstrated the following:aPTT was corrected by normal plasma, factor IX deficient plasma, but not by factor VIII deficient plasma. What factor assay should be performed next?
Factor VIII assay
The following factors are measured by either the PT or aPTT, EXCEPT:
Factor XIII
Thromboelastography (TEG) is a methodology used to assess blood coagulation. The prothrombin time (PT) and activated partial thromboplastin time (APTT) are more commonly used. All of the following are things that TEG can assess that the PT and APTT cannot assess EXCEPT?
Factor deficiencies
