Indications for hemostatic evaluation:

• Suspected bleeding tendency
• Bleeding tendency discovered in any family member
• Abnormal coagulation assays report during routine/pre surgery evaluation
• Unexplained diffuse bleeding during or after surgery or following trauma

Differential Diagnosis of bleeding problems 

• No bleeding disorder- Symptoms do not reflect bleeding disorder and have another explanation. (Ex: Surgical bleed which is not due to a bleeding disorder)
• Possible bleeding disorder- The laboratory findings are non-diagnostic and bleeding history is considered equivocal Ex: Unexplained serious bleed with one surgical procedure, unexplained menorrhagia without other bleeding problems.
• Definite bleeding disorder undefined or indeterminate type- Bleeding history is consistent with a bleeding disorder however lab findings are non diagnostic or not available.
• Definite bleeding disorder with a defined cause – Symptoms and lab findings are considered diagnostic of a bleeding disorder

Classification of diseases of hemostasis

• Inherited
  • Deficiency of coagulation factor- 8, 9, 2, 5, 7, 9, 11, 13, VWF.
  • Platelet function disorders- Glanzmanthrombasthenia, Bernard Soulier syndrome, platelet granule disorders.
  • Fibrinolytic disorders- Antiplasmin deficiency, plasminogen activator inhibitor 1 deficiency.
  • Vascular- Hemorrhagic telangiectasia.
  • Connective tissue disorders – EhlerDanlos syndrome.
• Acquired
  • Liver diseases- Cirrhosis, acute hepatic failure, liver transplantation, TPO  deficiency.
  • Renal failure
  • Vitamin K deficiency- Malabsorption syndrome, hemorrhagic disease of new born, prolonged antibiotic therapy, malnutrition
  • Hemorrhagic disorders- AML particularly APML, myelodysplasia, monoclonal gammopathy, essential thrombocythemia
  • Acquired antibodies against coagulation factor- Neutralizing antibodies against F V, VIII, XII which leads to accelerated clearance of factor Ex: Acquired VWD, Hypoprothrombinemia  associated with APLA.
  • DIC- Sepsis, malignancies, trauma, obstetric complications
  • Drugs- Anti platelet agents, anticoagulants, antithrombins, thrombolytic, hepatotoxic agents, Ginkgo biloba
  • Vascular- Non palpable purpura (Senile, solar, factitious, use of steroids, vitamin C deficiency, child abuse, amyloidosis etc)
  • Massive blood transfusion
  • Hypothyroidism
  • Other conditions causing thrombocytopenia

Investigations

• Complete hemogram including peripheral smear
• Screening tests- PT, APTT, TT, Fibrinogen
  • Coagulation proteins need to decrease to different low levels before the various screening tests show an abnormality.Ex: Most commercial APTT detect decrease in factor VIII when protein level decreases to 35%-45% of normal and XII and HMWK at levels of 10-15% of normal.PT is prolonged once F VII levels are below 35%
• Mixing studies- 
  • If PT/APTT are prolonged.
  • Test correction in mixing study indicates a deficiency state
  • Lack of correction indicates specific factor inhibitor or lupus anticoagulant.
  • Factor VIII inhibitors are time and temperature dependent. Hence test must be repeated after incubating the patient plasma with normal standard plasma at 37 degree C for 1-2 hrs)
• Factor assays- Based on PT, APTT and mixing study results.
• Platelet function test
• RFT  and LFT
• D-Dimer- If DIC is suspected
• Thyroid function test-hypothyroidism can cause increased bleeding
• Bleeding time and clotting time- They are not recommended now

If asymptomatic, investigate the patient if 

• PT >5 Sec than control
• APTT >8 Sec than control
• Immediate first step is to do mixing study to differentiate factor deficiency from presence of inhibitors

Approach to diagnosis:

Note: Deficiency of factor 12, HMWK, and Prekallikrein do not have with bleeding tendency

Thrombocytopenia

Introduction:

• It is a condition in which platelet count is less than 1.5 lac/cmm.
• But abrupt drop in platelet count, with platelet count still above 1.5 lac /cm, is significant and should be investigated
• Platelet count of 1 lac-1.5 lac/cmm with patient being stable for >6 months, does not indicate disease and does not need further evaluation.
• Following are thrombocytopenic emergencies. These conditions have to be excluded first, before considering other causes of thrombocytopenia, as they can be fatal if not treated urgently.
  • Heparin induced thrombocytopenia
  • Thrombotic thrombocytopenic purpura
  • Disseminated intravascular coagulation
  • Catastrophic antiphospholipid antibody syndrome
  • Primary immune thrombocytopenia with bleeding
  • Post-transfusion purpura

Causes of thrombocytopenia

• Pseudo thrombocytopenia.
  • Platelet agglutination.
  • Platelet satellitism.
  • Antiphospholipid antibodies.
  • GpIIa, IIIa antibodies.
  • Giant platelets.
• Impaired platelet production
  • Congenital (Auto dominant)
    • MYH9 related- May Hegglin anomaly, Fechtner syndrome, Epstein syndrome, Sebastin syndrome.
    • Mediterranean macro thrombocytopenia
    • Familial platelet syndrome with predisportion to AML
    • Thrombocytopenia with linkage to chromosome 10
    • Paris Trousseau syndrome
    • Thrombocytopenia with radial synostosis
  • Congenital (Autosomal Recessive)
    • Congenital amegakaryocytic thrombocytopenia
    • Thrombocytopenia with absent radii syndrome
    • Bernard Soulier syndrome
    • Gray PL syndrome
    • X- Linked thrombocytopenia
    • Wiskott Aldrich syndrome
    • X-linked thrombocytopenia with dyserythrocytosis
  • Acquired
    • Marrow infiltration- leukemia, lymphoma, myelofibrosis
    • Infectious disease- HIV, Parvo virus, Dengue, viral fever, malaria, CMV, E. Coli, shigella, mycobacteria, Rickettsia
    • Radiotherapy, Chemotherapy.
    • Folic acid, Vitamin- B-12 deficiency
    • Drug induced- Sulfa antibiotics, valproic acid
    • Paroxysmal nocturnal hemoglobinuria
    • Aplastic anemia
    • MDS
    • HLH 
    • Acquired pure amegakaryocytic thrombocytopenia (May be associated with other autoimmune disorders, rarely may progress to MDS/ aplastic anemia, Treated with immunosuppressive therapy -ATG with Cyclosporine)
    • Alcoholism
• Accelerated platelet destruction
  • Immune mediated
    • Immune thrombocytopenic purpura
    • Secondary immune thrombocytopenia- Infection (Hepatitis C, H. Pylori), pregnancy related, lymphoproliferative disorders, collagen vascular disease. Ex: SLE, RA, APLA, vaccination related
    • Allo immune thrombocytopenia.
    • Neonatal thrombocytopenia purpura
    • Post transfusion purpura
    • Drug induced thrombocytopenia
  • Non immune mediated
    • Thrombotic microangiopathy – TTP, HUS, DIC, Eclampsia/HELLP syndrome, catastrophic APLA
    • Septicemia
    • Infections- Dengue, HIV, Malaria
    • Kasabach Meritt syndrome (Large Hemangioma)
    • Platelet destruction by artificial surfaces
    • Gestational thrombocytopenia
    • Splenomegaly/ hypersplenism
    • Massive transfusion (Hemodilution related)
    • Post-surgical thrombocytopenia
    • Heparin induced thrombocytopenia
    • Other drug induced thrombocytopenia
    • Extracorporeal circuit/ Intravascular devices-
      • Cardiopulmonary bypass surgery (Often platelet count falls to around 50,000/cmm, associated with platelet dysfunction, No benefit of transfusion of platelets)
      • Intra-aortic balloon pumps
      • Extracorporeal membrane oxygenation
    • Decreased platelet survival associated with cardiovascular disease- congenital cyanotic disease, valular heart disease, cardiomyopathy  
    • Hypothermia related thrombocytopenia

Clinical manifestations of thrombocytopenia (Spontaneous bleeding is seen only when platelet count drops to less than 20,000/cmm)

• Purpura- skin (Dry purpura), Oral mucosal bleeding (Wet purpura). Wet purpura is a sign of impending serious internal bleeding such as intracranial bleeding.
• Increased PV bleeding, hematochezia, malena, epistaxis, hemoptysis, hematemesis

Investigations

• CBC- To know whether patient has isolated thrombocytopenia or pancytopenia.
• Peripheral smear examination:
  • Pseudo thrombocytopenia (EDTA induced platelet clumping, giant platelets, platelet satellitism etc)
  • RBC fragments suggest microangiopathy- TTP, HUS, or DIC
  • Moderately enlarged platelets- Seen in ITP and other conditions with accelerated platelet destruction
  • Small platelets- Seen in Wiskott aldrich syndrome
  • Macrocytosis and hypersegmented neutrophils are seen in megaloblastic anemia
  • Target cells are seen in liver diseases
  • Abnormal WBCs are seen in acute leukemias and MPN
  • Dysplastic changes such as Pelger Huet anomaly suggest myelodysplastic syndrome
  • Leucoerythroblastic reaction is suggestive of bone marrow infiltration or myelofibrosis
  • Toxic changes and granulocyte "left shift" suggest septicemia
  • Atypical lymphocytes suggest viral infection such as dengue
  • Parasites Ex: malaria
  • White cell inclusions (Dohle bodies) suggest hereditary macrothrombocytopenia (MYH9 related)
• LFT
• RFT
• LDH
• Blood cultures- Bacteremia, fungemia
• ANA test
• Direct antiglobulin test- To exclude immune hemolysis accompanying ITP (Evans syndrome)
• Coagulation assays- APTT,PT (INR), TT, fibrinogen, D-dimer assay- To rule out DIC
• Lupus Anticoagulant assay (nonspecific APL antibody syndrome inhibitor), anticardiolipin and anti beta2 Glycoprotein I assays- For APLA
• Serum protein electrophoresis, IgG,IgM,IgA levels: Monoclonal in case of  ITP associated with lymphoproliferative disorder and polyclonal in case of chronic hepatitis
• HIV serologic study
• BM aspiration, biopsy- Assesses megakaryocyte  numbers and morphology; exclude primary BM disorder, Metastasis, Goucher disease, leukemia, megaloblastic anemia
• USG abdomen- to rule out chronic liver disease and to check for organomegaly and enlarged abdominal/pelvic lymph nodes

Specialized tests

• Platelet associated IgG- It is not useful due to high prevalence in normal population as well
• Drug dependent increase in  platelet associated IgG- It is specific assay for drug induced ITP
• Drug dependent platelet activation test (e. g.  Platelet serotonin release assay) or PF4 heparin (or PF4 –polyanion) ELISA- Done for diagnosis of heparin induced thrombocytopenia
• Radionuclide platelet lifespan study with imaging (Ex: ¹¹¹In platelet survival study)- Helps in defining the mechanism of thrombocytopenia, also helps to  identify an accessory spleen  in post-splenectomy patients)
• Reticulated platelet count: 
  • Counting of newly released circulating platelets which have RNA
  • Helps in discriminating between thrombocytopenia due to BM failure (RPC is decreased) and hyperdestructive thrombocytopenia (RPC is increased.
  • Normal -3-20%

Diagnostic algorithm (For neonatal thrombocytopenia- Refer consultative hematology section)

General principles of management

• Avoid drugs that impair hemostasis –Ex: Alcohol, antiplatelet agents, anticoagulants
• Avoid invasive procedure including IM injections
• Stop suspected drug causing thrombocytopenia
• If life threatening bleed – Transfuse platelets irrespective of mechanism of thrombocytopenia
• Do not give prophylactic platelets to patients who are stable (ITP, aplastic anemia, MDS etc)
• Keep a cut-off PL count > 50000/cmm for invasive procedures like – Thoracentesis, paracentesis and liver biopsy.
• No platelets should to be given in patients strongly suspected or confirmed HIT, TTP, or HUS (As thrombotic complications may increase)

Causes of thrombocytopenia with anemia

• TTP
• Evan syndrome
• DIC
• HELLP syndrome
• HUS
• Drugs - Quinine, Simvastatin, interferon, calcineurin inhibitors, clopidogrel
• Malignant hypertension.
• Infections
• Viral-CMV, Adeno, HSV, AIDS, HCV
• Bacterial: Meningococcus, Pneumococcus, H. Pylori
• Fungal 
• Autoimmune: Lupus nephritis, acute scleroderma, Autoimmune hepatitis
• Malignancy
• Catastrophic APLA
• Progressive systemic sclerosis
• Heparin induced thrombocytopenia
• Lymphoma – HD, CLL
• Liver disease
• MDS, leukemia, Myelofibrosis, aplastic anemia, megaloblastic anemia

Causes of thrombocytopenia with thrombosis

• Heparin induced thrombocytopenia
• Malignancies          
• DIC
• TTP
• HUS
• SLE
• Warfarin induced gangrene
• Sepsis
• APLA
• PNH

Figures:

Figure 12.10.1- Pseudothrombocytopenia due to platelet clumps