Coagulation Flashcards
Amyloidosis - Factor, test
X (decreased) Thrombin time (increased)
Conditions affecting vWF levels
Increased: Acute phase reaction, OCPs, pregnancy, neonates
Decreased: Type O blood group
Protein S
Carrier of protein C.
In turn 60% bound to C4BP.
Reptilase time
Snake venom (Batroxobin) from Bothrops snake»_space; Directly cleaves fibrinogen. Unlike thrombin time, not sensitive to heparin.
Time-dependent prolongation on mixing study
fVIII inhibitor
Platelet aggregation - Phases
1st phase: ADP release
2nd phase: More ADP release, TXA2 release.
Bernard-Soulier
CD42 (Gp1b/V/X)»_space; Macrothrombocytopenia
Impaired aggregation with ristocetin
Decreased response to thrombin-induced aggregation
Glanzmann’s thrombasthenia
GPIIb (CD41) / IIIa (CD61) abnormality. Normal platelet count.
No aggregation except with ristocetin.
Alpha-granule deficiencies
Gray platelet (retain P-selectin) Quebec platelet (excess u-PA degrades granule) Paris-Trousseau
Dense-granule deficiencies
Chediak-Higashi
Wiskott-Aldrich
Hermansky-Pudlak
Storage pool deficiencies - Testing
No second wave on aggregation.
Diminished responses to collagen, arachidonic acid
Note: Both of above also true of aspirin effect
vWD - I, III
I - Autosomal dominant. Mild, treatable with DDAVP. Normal multimers.
III - Autosomal recessive. Total absence.
vWD - 2A, 2B, plt-type
2A - Most common after I. Very few large multimers. Low activity:antigen ratio. Acquired forms resemble this.
2B - Rare. Exon 28 abnormality»_space; increased Gp1b affinity. Few large multimers. Abnormal RIPA. DDAVP will cause thrombocytopenia.
Plt-type - Gp1b on platelet has higher affinity for vWF. Abnormal RIPA. Fewer multimers. Distinguish with cryo challenge
vWD - 2N, 2M, Plt-type
2N - Abnormal fVIII binding site, presents like Hemophilia A.
2M - Decreased Gp1b binding affinity. Very low activity.
Hemophilia A - Congenital & acquired
Congenital: Usually intron 22 inversion. XLD, can be seen in women in Turner, homozyg, lyonization
Acquired: Rare, elderly with new bruising
Minor hemophilias
Hemophilia C (factor XI, jews, autosomal. No recombinant available) fIX (anaphylaxis with repletion) f12 (maybe thrombogenic?) f7 (maybe also thrombogenic?) f13
Dysfibrinogenemias
Qualitative dysfunction, only partially corrects on mixing due to competitive inhibition.
Diagnose with thrombin time (more sensitive than reptilase time)
Alpha-2 antiplasmin deficiency
Test: SLOW euglobulin clot lysis. Normal other coags.
TTP/HUS
Normal PT, PTT, fibrinogen, D-dimer. Platelet-rich clots.
Heparin resistance
AT-III deficiency
Increased heparin clearance or binding
Homocysteinemia
Endothelial dysfunction
Lens dislocation, peripheral neuropathy, maybe low folate?
Hypercoagulability of pregnancy
General increase in all factors
Decrease in protein S
APC resistance
Venous stasis
Platelet collagen receptors
GPVI (major, plays signaling role, deficiency in Japanese) Integrin a2b1 (GpIa/IIa)
Wiskott-Aldrich
XLD
Thrombocytopenia, eczema, immunodeficiency
Cytoskeletal abnormality, impaired signal transduction
Low IgM, high IgE and IgA
VASP
Cone & Plate analysis
VASP: Flow-based method, gold-standard for P2Y12 inhibitor effect.
Cone & Plate: In vitro method studying shear-induced adhesion. Affected by Hct, plt count, meh,.
May-Hegglin
Chediak-Higashi
Fechtner
May-Hegglin - Dohle-like bodies in neutrophils. MYH9
Chediak-Higashi - Peroxidase+ granules in many leukocytes
Fechtner - May Hegglin + Alport syndrome
Congenital amegakaryocytosis
MPL gene mutation
Specimen types in coag testing
Most: Citrated plasma (3.2% NaCit)
Flow: Whole blood
Plt agg: Platelet rich and poor plasma (still collect in blue top)
PFA-100: Patterns
ASA: Col/Epi prolonged, Col/ADP normal
Plavix: Variable, both may be prolonged
BSS, GT: Both prolonged
ITP targets
Usually GpIIb/IIIa or Ib/V/X
IIb/IIIa inhibitors
Abciximab (Fab fragments)
Tirofiban (nonpeptide)
Eptifibatide (oligopeptide)
Plavix
Blocks P2Y12 (irreversibly) Prodrug, activated by 2C19
Scott syndrome
Disorder of flippase
Abnormal Annexin V on flow
Shortened PT
TXA2 metabolites
Metabolized to TxB2, then to 11-dehydroTxB2 in urine.
Plt aggregation - Types, agonists
Types: Turbidometric (gold standard), impedance, lumiaggregometry
Agonists: Col, ADP, Epi, AA, Thrombin, TRAP, Ristocetin, U44619
Aggregometry - Aspirin, plavix
Aspirin: Impaired TXA2 production. No second wave after ADP/Epi agonism.
Plavix: No first wave with ADP agonist.
Falsely elevated plt count on hematology analyzer
Red cell fragments (schistocytes, AML)
Microorganisms
NAIT
Usually due to HPA-1a > 4b (Asian) antibodies. Treat with maternal platelets.
Ddx: Maternal ITP with placental transfer (mom should be thrombocytopenic)
Fonio method
To estimate platelet count, multiply the number of platelets seen on a 1000x field by 20.
Plt histogram
Right skew
ITP Tx
Steroids, IVIG
Second-line: Rituximab, other immunosuppressants
PAR-1
PAI-1
PAR-1 - Thrombin receptor on platelets
PAI-1 - Plasminogen activator inhibitor (serpine antifibrinolytic protein on…endothelium?)
Jackass platelet trivia
10^11 produced per day
7-10d lifespan
Clinical presentation of platelet-type and coagulation-type bleeding
Platelet-type: Mucocutaneous bleeding, excessive bleeding from minor trauma
Coagulation-type: Deep or delayed bleeding, bruising, hemearthroses
TPO agonists
eg Romiplostim, eltrombopag
May cause bone marrow fibrosis (reticulin deposition)
Weibel-Palade bodies
Contain vWF, P-selectin
VitK dependent factors.
What conditions affect these?
2, 7, 9, 10, C, S
Warfarin, antibiotics, IBD
Factor half-lives
fVII - 6hrs (shortest)
fVIII - 12hrs
fIX - 24hrs
fXIII - week (longest)
NovoSeven
Activated factor 7, can be used as bypass agent. Very short lived.
Factor dosing
fVIII - Bw(kg) x %change, divided by 2.
fIX - Bw(kg) x %change
Pharmacogenetics of warfarin
VKORC polymorphisms may confer resistance
Metabolized by CYP2C9
Early activators of intrinsic pathway
HMWKgen activates fXII which activates pre-kallikrein.
HMWKgen deficiency does NOT correct on mixing aPTT.
fXIII treatment
Cryoprecipitate
Corifact (recombinant fXIII)
Brill-Edwards regression
Relates aPTT to anti-Xa activity (0.3-0.7 goal)
Indications for thrombophilia testing
Thrombosis <50yo
Unusual thromboses
Recurrent thromboses
Primary family member with thrombophilia
APC resistance
Protein C assay (functional)
Protein S assay (functional)
APC resistance: Spike APC into patient plasma, look for expected prolongation of clotting
Protein C assay: Use protein C activator (not APC itself)
Protein S assay: Also spikes APC, looking for expected prolongation of clotting
AT3 Testing
Chromogenic reagent is normally generated by thrombin. Add heparin and patient sample (AT). Normally, chromogenic substance should not be generated.
Causes of decreased AT3
Liver disease
Nephrotic syndrome
Thrombosis? IBD? Pregnancy?
L-asparaginase
APCR elevation
Factor V leiden Any inhibitors (LAC, heparin) Factor deficiencies
DRVVT
Protac snake venom activates protein C. More protein C prolongs clotting time.
Used as screening test for LAC.
Purpura fulminans
Deficiency of protein C, as seen in DIC, newborns, warfarin without bridging, and homozygous C deficiency.
INR calculation
ISI calculation
(PT / geomean) ^ ISI
ISI is slope of reference PT means to lot PT means
Heparin side effects
Bleeding
Osteoclast activation, osteoblast suppression»_space; osteoporosis
Protamine
Arginine rich, positively charged antidote to UFH > LMWH
Liver transplant phases
Anhepatic stage: Activation of fibrinolysis, loss of factors»_space; BLEEDING
Postreperfusion: Correction o fibrinolysis, slow replenishment of factors, but plt sequestration
Postoperative: HYPERCOAGULABLE
Heparin cofactor II
Minor target of heparin (adjunctive to AT3). Inactivates only IIa.
Factors produced exclusively in liver, or not in liver at all
Only made in liver: PAI-1, Plasminogen
Not made in liver: vWF,
Josso loop
In vivo activation of factor IX by TF-VIIa complex
At what dilution would an 8-bethesda inhibitor reduce activity by 75%?
1: 4 - 25% residual ***
1: 8 - 50% residual
1: 16 - 75% residual
TFPI
Thrombomodulin
TFPI - Inhibits TF-VIIa complex
Thrombomodulin - Activates protein C, has minor procoagulant and anti-inflammatory functions
Germline RUNX1 mutation
Thrombocytopenia, increased risk of AML
Chromogenic factor X
For warfarin monitoring of patients with LAC.
Activated clotting time (ACT)
Uses whole blood and a contact activator.
For very high heparin levels (eg, bypass)
Takes >100 sec to result
Heparin assay
Titrate heparin using protamine