L.15 Lab Investigation of Haemostatic Disorders Flashcards
(109 cards)
1
Q
What is the purpose of capillary blood samples?
A
Used for immediate, point-of-care analysis, e.g., INR home monitoring or outpatient coagulation clinics.
2
Q
What are the limitations of capillary blood samples?
A
Limited in volume and scope.
3
Q
What type of blood is collected using vacutainers?
A
Venous blood.
4
Q
Why is careful handling important for venous blood samples?
A
To preserve sample integrity.
5
Q
What is the mechanism of Sodium Citrate as an anticoagulant?
A
Reversibly binds calcium.
6
Q
What color tube is used for Sodium Citrate?
A
Light blue or green.
7
Q
What is Sodium Citrate used for?
A
Coagulation studies, e.g., PT, APTT.
8
Q
What is the mechanism of EDTA?
A
Irreversibly chelates calcium.
9
Q
What color tube is used for EDTA?
A
Pink or purple.
10
Q
What is EDTA used for?
A
Full blood count, platelet count.
11
Q
What does Heparin inhibit?
A
Thrombin (Factor IIa).
12
Q
What color tube is used for Heparin?
A
Green.
13
Q
What is Heparin primarily used for?
A
Biochemistry; not ideal for coagulation studies.
14
Q
What is the mechanism of Acid Citrate Dextrose (ACD)?
A
Binds calcium + nutrient support.
15
Q
What color tube is used for ACD?
A
Yellow.
16
Q
What is ACD used for?
A
Tissue typing, some molecular studies.
17
Q
What is the purpose of serum tubes?
A
Allows clotting for serum required tests.
18
Q
What color tube is used for serum tubes?
A
Red or gold.
19
Q
What critical factor must be maintained in anticoagulant ratio?
A
Use tri-sodium citrate at a final concentration of 105–109 mmol/L, maintaining a 1:9 ratio.
20
Q
What is a recommended venepuncture technique?
A
Use minimal tourniquet time, avoid venous occlusion.
21
Q
What gauge needles are recommended for venepuncture?
A
19–22 gauge needles.
22
Q
What should be avoided to ensure sample integrity?
A
Avoid underfilling or overfilling tubes.
23
Q
What hematocrit level may require citrate adjustment?
A
Elevated hematocrit levels (>55%).
24
Q
What is the ideal time frame for testing blood samples after collection?
A
Within 4 hours of collection.
25
True or False: Samples should be drawn from lines containing heparin.
False.
26
What is the sample type used for the Platelet Count test?
EDTA (FBC tube)
## Footnote
Used to screen for thrombocytopenia
27
Which pathway does the Prothrombin Time (PT) assess?
Extrinsic pathway (Factors II, V, VII, X, I)
## Footnote
Used primarily for warfarin monitoring
28
What does the International Normalised Ratio (INR) standardize?
Prothrombin Time (PT)
## Footnote
Adjusts warfarin therapy
29
What is the sample type for the Activated Partial Thromboplastin Time (APTT)?
Sodium citrate
## Footnote
Monitors heparin therapy and detects intrinsic defects
30
What does the Thrombin Time (TT) assess?
Final common pathway (Fibrinogen → Fibrin)
## Footnote
Detects thrombin inhibitors and fibrinogen disorders
31
What is assessed in the Fibrinogen assay?
Fibrinogen concentration/function
## Footnote
Screens for hypofibrinogenaemia and DIC
32
What factors does the PT assess for deficiencies?
Factors II, V, VII, X, and fibrinogen (I)
## Footnote
Important for monitoring warfarin therapy
33
What is the normal range for Prothrombin Time?
~10–14 seconds (lab-specific)
## Footnote
Indicates normal clotting function
34
What conditions can a prolonged PT indicate?
* Vitamin K deficiency
* Liver disease
* Warfarin overdose
## Footnote
Important for clinical diagnosis
35
What is the formula for calculating INR?
INR = (Patient PT / Control PT)^ISI
## Footnote
ISI = International Sensitivity Index for the thromboplastin used
36
What INR range is considered normal for non-anticoagulated individuals?
1.1 or less
## Footnote
Indicates normal coagulation status
37
What is the typical therapeutic INR range for warfarin?
2.0–3.0
## Footnote
Indicates effective anticoagulation
38
What action should be taken if INR is >3.0–4.5?
Reduce warfarin dose
## Footnote
Indicates supratherapeutic level
39
What should be done if INR is 4.5–10.0 with no bleeding?
Omit 1–2 doses, monitor INR, consider vitamin K if needed
## Footnote
Prevents potential bleeding complications
40
What is the recommended action for INR >10 with no bleeding?
Hold warfarin, consider oral vitamin K
## Footnote
Critical for managing high INR levels
41
What should be done for any INR with minor bleeding?
Hold warfarin, monitor INR, possibly give vitamin K or coagulation factor concentrate
## Footnote
Addresses immediate risk of bleeding
42
What is the International Normalised Ratio (INR)?
A measure sensitive to physiological and external influences affecting coagulation, particularly in patients on warfarin therapy.
## Footnote
The INR is used to monitor the effectiveness of anticoagulation therapy.
43
Which medications can influence the INR?
Medications that can increase or decrease INR include:
* Warfarin
* Antibiotics (e.g. metronidazole)
* Antifungals
* NSAIDs
* Antiepileptics
## Footnote
These medications can interfere with the metabolism of warfarin.
44
How does liver disease affect INR?
Liver disease impairs the synthesis of vitamin K–dependent clotting factors (II, VII, IX, X), leading to prolonged INR.
## Footnote
This is due to the liver's role in producing these crucial factors.
45
What dietary factor can reduce INR?
High intake of dietary Vitamin K can reduce INR by promoting clotting factor synthesis.
## Footnote
Foods like green leafy vegetables (e.g., spinach, kale, cabbage) are rich in Vitamin K.
46
How does alcohol consumption affect INR?
Chronic alcohol use impairs liver function (↑INR), while acute use can initially inhibit metabolism of warfarin (↑INR).
## Footnote
The effects may vary based on the duration and quantity of alcohol consumed.
47
What is the effect of smoking on INR?
Smoking induces hepatic enzymes, potentially lowering the effect of warfarin (↓INR).
## Footnote
This can lead to a need for increased warfarin dosage.
48
How do physical or emotional stress influence INR?
Physical or emotional stress may affect metabolism and response to medications, indirectly influencing INR.
## Footnote
Stress can alter hormonal levels that affect coagulation.
49
What are environmental factors that can affect INR?
Travel or altitude changes may alter dietary patterns or metabolism, indirectly affecting INR.
## Footnote
These changes can impact the absorption and efficacy of medications.
50
What does Activated Partial Thromboplastin Time (APTT) evaluate?
APTT evaluates the intrinsic and common coagulation pathways.
## Footnote
It measures the time taken for clot formation after activation of contact factors.
51
Which factors are assessed in APTT?
Factors assessed include:
* XII
* XI
* IX
* VIII (intrinsic)
* X
* V
* II (prothrombin)
* I (fibrinogen) (common)
## Footnote
These factors are crucial for the coagulation cascade.
52
What is the method for conducting APTT?
The method includes:
1. Activation with silica or kaolin
2. Incubation at 37°C for 5 minutes with phospholipid
3. Initiation with calcium chloride
4. Measurement of clotting time
## Footnote
This sequence ensures accurate measurement of intrinsic pathway activity.
53
What is the reference range for APTT?
The reference range for APTT is 21–35 seconds, depending on laboratory-specific reagents.
## Footnote
Variations can occur based on testing methods.
54
What are the uses of APTT?
APTT is used to:
* Monitor unfractionated heparin therapy
* Screen for inherited factor deficiencies (e.g., haemophilia A/B)
* Detect presence of lupus anticoagulant or specific inhibitors
## Footnote
These applications are vital for assessing coagulation disorders.
55
What is the purpose of Thrombin Time (TT)?
TT assesses the conversion of fibrinogen to fibrin by adding thrombin directly to the plasma.
## Footnote
This test evaluates the final step in the coagulation cascade.
56
What is the normal range for Thrombin Time (TT)?
The normal range for TT is 15–23 seconds.
## Footnote
Prolonged TT can indicate coagulation abnormalities.
57
What can cause prolonged Thrombin Time (TT)?
Causes of prolonged TT include:
* Dysfibrinogenaemia
* Hypofibrinogenaemia
* Presence of inhibitors (e.g., heparin contamination, elevated fibrin degradation products)
## Footnote
These conditions can interfere with the conversion of fibrinogen to fibrin.
58
What is Reptilase Time (RT)?
A test that distinguishes whether a prolonged TT is due to heparin contamination or a fibrinogen defect.
## Footnote
TT stands for Thrombin Time, which measures the time it takes for a clot to form in a sample of plasma after thrombin is added.
59
What is the purpose of the Reptilase test?
To distinguish between heparin effect and fibrinogen disorders in cases of prolonged TT.
60
What is the mechanism of Reptilase?
Reptilase is a thrombin-like enzyme from Bothrops atrox snake venom that cleaves fibrinogen to fibrin and is not inhibited by antithrombin or heparin.
61
What does a prolonged TT and normal RT indicate?
Heparin effect likely.
62
What does a prolonged TT and prolonged RT indicate?
Likely a fibrinogen disorder (qualitative or quantitative).
63
What is the purpose of the Fibrinogen Assay – Clauss Method?
To quantify functional fibrinogen concentration in plasma.
64
What is the first step in the Fibrinogen Assay – Clauss Method?
Dilute plasma with Owren’s buffer (1:9 dilution).
65
What is done after diluting plasma in the Fibrinogen Assay?
Add high concentration thrombin.
66
How is the time to clot formation related to fibrinogen concentration?
Time to clot formation is inversely proportional to fibrinogen concentration.
67
What is the normal range for fibrinogen concentration?
1.5 – 4.0 g/L.
68
What conditions can the Fibrinogen Assay help diagnose?
* Hypofibrinogenaemia
* Dysfibrinogenaemia
* DIC
* Liver dysfunction.
69
What is the role of fibrinogen in the coagulation cascade?
It serves as the substrate for thrombin and forms the structural backbone of the fibrin clot.
70
What is afibrinogenaemia?
Complete absence of fibrinogen.
71
What is dysfibrinogenaemia?
Structurally abnormal fibrinogen with impaired function.
72
What is hypofibrinogenaemia?
Partial deficiency in fibrinogen quantity.
73
What is Disseminated Intravascular Coagulation (DIC)?
A condition causing consumption of fibrinogen due to widespread clotting.
74
What can cause severe haemorrhage related to fibrinogen levels?
Dilutional or consumptive loss of fibrinogen.
75
How does liver disease affect fibrinogen levels?
It leads to impaired synthesis of fibrinogen.
76
What is the purpose of Mixing (Correction) Studies?
To distinguish between a factor deficiency and the presence of an inhibitor when PT or APTT is prolonged
## Footnote
Mixing studies help determine if a prolonged PT/APTT is due to a deficiency in a coagulation factor or an inhibitor affecting the coagulation process.
77
What is the procedure for Mixing (Correction) Studies?
1. Mix equal parts of patient plasma and normal pooled plasma. 2. Repeat the coagulation test (PT/APTT) immediately (T0) and after incubation at 37°C for 60 minutes (T60)
## Footnote
This procedure helps observe changes in clotting times that indicate the underlying issue.
78
What does correction of clotting time indicate in Mixing Studies?
Likely factor deficiency
## Footnote
If the clotting time normalizes after mixing, it suggests that a factor deficiency is the cause of the prolonged PT/APTT.
79
What does no correction or worsening of clotting time after incubation suggest?
Presence of an inhibitor, such as a lupus anticoagulant or specific factor inhibitor
## Footnote
This indicates that the problem may not be due to a deficiency but rather an inhibiting substance in the plasma.
80
What is the purpose of Factor Assays?
To quantify individual coagulation factor levels and confirm suspected deficiencies
## Footnote
Factor assays help identify specific deficiencies in coagulation factors that may cause bleeding disorders.
81
What are the indications for conducting Factor Assays?
* Abnormal PT or APTT
* History of bleeding diathesis
* Family history of inherited bleeding disorders
## Footnote
These indications help determine when to test for specific factor deficiencies.
82
What is the approach to conducting Factor Assays?
Conduct assays for factors VIII, IX, XI, etc., depending on suspected pathway
## Footnote
This targeted approach allows for the identification of specific deficiencies based on clinical suspicion.
83
How many consistently abnormal values across separate samples confirm a deficiency?
Three
## Footnote
This criterion helps ensure the reliability of the test results.
84
What is the significance of D-dimer in tertiary haemostasis?
A marker of fibrinolysis and recent thrombus formation
## Footnote
D-dimer is produced when cross-linked fibrin is broken down, indicating ongoing thrombotic processes.
85
What type of sample is used for the Quantitative D-dimer Test?
Citrated plasma
## Footnote
Citrated plasma is used to prevent coagulation during the testing process.
86
Is the D-dimer test highly sensitive or specific?
Highly sensitive, but not specific
## Footnote
While it can effectively rule out thrombotic conditions, elevated levels can occur in various conditions.
87
What does an elevated D-dimer suggest?
* Deep vein thrombosis (DVT)
* Pulmonary embolism (PE)
* Disseminated Intravascular Coagulation (DIC)
* Surgery, trauma, malignancy, pregnancy, elderly
## Footnote
Elevated levels can indicate several thrombotic conditions and other risk factors.
88
What is the negative predictive value of a normal D-dimer in low-risk patients?
>98%
## Footnote
This means that a normal D-dimer result is very effective in ruling out DVT/PE in low-risk individuals.
89
What is Deep Vein Thrombosis (DVT)?
Formation of a thrombus in deep veins, usually legs
## Footnote
DVT can lead to serious complications, including pulmonary embolism.
90
What are common symptoms of Deep Vein Thrombosis (DVT)?
* Calf pain
* Swelling
* Redness
## Footnote
These symptoms are indicative of DVT but may vary among patients.
91
What is Pulmonary Embolism (PE)?
Thrombus from DVT travels to the pulmonary arteries
## Footnote
PE can be a life-threatening condition requiring immediate medical attention.
92
What are common symptoms of Pulmonary Embolism (PE)?
* Sudden chest pain
* Dyspnoea
* Tachycardia
* Hypotension
## Footnote
These symptoms may indicate a serious medical emergency.
93
What is Disseminated Intravascular Coagulation (DIC)?
A pathological process involving widespread activation of coagulation, leading to consumption of platelets and clotting factors and secondary activation of fibrinolysis.
94
What are the causes of acute DIC?
* Sepsis/infection
* Major trauma or burns
* Obstetric complications (e.g. placental abruption)
* Liver failure
* Malignancy
95
What are the causes of chronic DIC?
* Advanced malignancies
* Obstetric syndromes (e.g. retained dead fetus)
* Myeloproliferative disorders
* Paroxysmal nocturnal haemoglobinuria (PNH)
96
What is the pathophysiology of DIC?
Thrombin and plasmin generated simultaneously, leading to formation and breakdown of fibrin.
97
What are the consequences of fibrin-platelet thrombi in DIC?
Cause microvascular occlusion and may lead to organ failure due to ischaemia.
98
What type of end-organ damage can occur in the kidneys due to DIC?
Acute tubular necrosis and renal failure.
99
What type of end-organ damage can occur in the liver due to DIC?
Hepatic dysfunction and jaundice.
100
What type of end-organ damage can occur in the lungs due to DIC?
Respiratory distress or failure.
101
What are some other potential complications of DIC?
CNS involvement, myocardial infarction, SIRS.
102
What are the laboratory findings in DIC for PT, APTT?
↑ Prolonged.
103
What does a low platelet count indicate in DIC?
↓ Thrombocytopenia.
104
What does low fibrinogen indicate in DIC?
↓ Low.
105
What does an elevated D-Dimer indicate in DIC?
↑ Elevated.
106
What is the thrombin time result in DIC?
↑ Prolonged.
107
What are schistocytes?
RBC fragments observed in blood film in DIC.
108
What is the role of D-dimer in diagnosing DVT/PE?
Rule out; normal D-dimer excludes with high confidence.
109
What is the role of D-dimer in DIC?
Monitor coagulopathy; elevated D-dimer with low fibrinogen supports diagnosis.
