Platelet

Platelet Result

(Reference range: 140-400 ×10⁹/L)

 

What is Thrombocytopenia?

Thrombocytopenia refers to a platelet count < 150 ×10⁹/L. It may be caused by reduced production, increased destruction, or splenic sequestration.

  • Mild: 100-150 ×10⁹/L
  • Moderate: 50-99 ×10⁹/L
  • Severe: < 50 ×10⁹/L (higher bleeding risk)

Common Causes

  • Viral infections (e.g. EBV, hepatitis, HIV)
  • Drugs (e.g. heparin, carbamazepine, sodium valproate)
  • Alcohol excess or liver disease
  • Immune thrombocytopenia (ITP)
  • Bone marrow suppression or infiltration
  • Disseminated intravascular coagulation (DIC)
  • Hypersplenism

Stepwise Clinical Approach

Step 1: Confirm and Repeat

Exclude spurious results from platelet clumping or poor sampling.

If mild and asymptomatic, repeat FBC in 1-2 weeks.

Also request:

  • Blood film: to assess platelet morphology, clumping, or abnormal cells
  • Liver function tests (LFTs): to assess for liver disease or alcohol-related thrombocytopenia
  • Clotting screen: to check for DIC or other coagulopathies
  • HIV and hepatitis screen: viral causes of thrombocytopenia
  • Vitamin B12 and folate: deficiency may cause bone marrow suppression

These tests help identify reversible or serious underlying causes early.

Step 2: Identify Red Flags

  • Platelets < 50 ×10⁹/L
  • Bleeding or bruising
  • Recent heparin use (possible HIT)
  • Concurrent anaemia or neutropenia
  • Splenomegaly or unexplained systemic illness

Urgent referral to haematology is warranted if any red flags are present.

Step 3: Review Medications and History

  • Check for recent viral illness or vaccination
  • Review current and recent medications
  • History of liver disease, alcohol intake, or autoimmune conditions?

Drug-induced or viral thrombocytopenia is common and often transient.

Step 4: Interpret Repeat Results

  • If platelets normalise: no further action needed
  • If persistent < 100 ×10⁹/L: refer to haematology for further investigation

Step 5: Monitor or Refer

  • If platelets 100-150 ×10⁹/L and asymptomatic: monitor 3-6 monthly
  • If count falls or symptoms appear: expedite referral
  • Always refer urgently if bleeding or platelets < 50 ×10⁹/L
 

What is Thrombocytosis?

Thrombocytosis refers to a platelet count > 450 ×10⁹/L. It may be reactive (secondary) or primary due to a myeloproliferative disorder.

Common Causes

  • Recent infection or inflammation (e.g. pneumonia, sepsis)
  • Iron deficiency anaemia
  • Post-splenectomy
  • Malignancy
  • Myeloproliferative disorders (e.g. essential thrombocythaemia)

Stepwise Clinical Approach

Step 1: Confirm and Repeat

Confirm isolated thrombocytosis and review blood film if available.

If mild and asymptomatic, repeat FBC in 4-6 weeks.

Also request:

  • CRP and ESR: to check for underlying inflammation or infection
  • Iron studies (Ferritin, Iron, TIBC): to exclude iron deficiency anaemia
  • Liver and renal function tests: to check for chronic disease states
  • Blood film: to assess platelet morphology and rule out myeloproliferative features

These tests help determine if thrombocytosis is reactive or suspicious for a primary cause.

Step 2: Identify Reactive Causes

  • Recent infections or inflammatory illnesses?
  • Evidence of iron deficiency anaemia?
  • History of surgery, trauma, or splenectomy?

If a reactive cause is likely, repeat bloods after recovery or iron treatment.

Step 3: Interpret Repeat Results

  • If platelets normalise: reactive cause confirmed
  • If persistently elevated: investigate further for primary thrombocytosis

Step 4: Monitor or Refer

  • If platelets < 600 ×10⁹/L and reactive cause identified: monitor 3-6 monthly
  • If platelets persistently > 600 ×10⁹/L without cause: refer to haematology for JAK2/MPL/CALR mutation testing

Step 5: Red Flags Requiring Urgent Action

  • Platelets > 1000 ×10⁹/L
  • Thrombosis or ischaemic symptoms (e.g. headache, erythromelalgia)
  • Splenomegaly
  • Other cytopenias or abnormal blood film

Urgent referral to haematology is indicated if any red flags are present.

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