Unit Converter
Platelets (Thrombocytes)
Synonyms
- Platelets
- Thrombocytes
- PLT
- Platelet count
- Thrombocyte count
- Platelet number
Units of Measurement
- 10⁹/L
- G/L
- Gpt/L
- cells/L
- 10³/µL
- 1000/µL
- 10³/mm³
- 1000/mm³
- K/µL
- K/mm³
- cells/µL
- cells/mm³
Universal Conversions
1 ×10⁹/L=1000 cells/µL=1 K/µL1\ \text{×10⁹/L} = 1000\ \text{cells/µL} = 1\ \text{K/µL}1 ×10⁹/L=1000 cells/µL=1 K/µL
Examples:
- 250 ×10⁹/L = 250 K/µL = 250,000/µL
- 50 ×10⁹/L = 50 K/µL = thrombocytopenia
- 800 ×10⁹/L = 800 K/µL = thrombocytosis
Description
Platelets are small anucleate cytoplasmic fragments derived from megakaryocytes in the bone marrow.
They are essential for:
- Primary hemostasis
- Clot formation
- Wound repair
- Inflammation & immunity
- Vascular integrity
Platelet counts are part of the complete blood count (CBC) and used in almost every medical specialty.
Physiological Role
- Adhesion to damaged endothelium
- Activation & shape change
- Aggregation to form platelet plug
- Release of granule contents (ADP, serotonin, thromboxane)
- Support of coagulation cascade (factor V, VIII interactions)
Life span: 7–10 days
Destroyed in spleen, liver, and reticuloendothelial system.
Clinical Significance
HIGH Platelets (Thrombocytosis)
Types
1. Reactive (Secondary) Thrombocytosis - most common
- Infection
- Inflammation
- Trauma
- Post-surgery
- Iron deficiency
- Malignancy
- Splenectomy
- Hemolysis
2. Primary (Clonal) Thrombocytosis
Due to myeloproliferative neoplasms (MPNs):
- Essential thrombocythemia (ET)
- Polycythemia vera (PV)
- Primary myelofibrosis (PMF)
- CML (less commonly)
Complications
- Thrombosis
- Stroke
- MI
- Pregnancy complications (ET)
- Microvascular symptoms (erythromelalgia)
LOW Platelets (Thrombocytopenia)
Major Causes
1. Decreased Production
- Aplastic anemia
- Leukemia
- Myelodysplastic syndrome
- Chemotherapy
- HIV/Hep C
- Alcoholism
- Nutritional deficiency (B12, folate)
2. Increased Destruction
- Immune thrombocytopenia (ITP)
- Drug-induced (heparin, antibiotics, antiepileptics)
- DIC
- TTP/HUS
- Hypersplenism
3. Dilutional
- Massive transfusion
- Major surgery
Bleeding Risk
- >100 ×10⁹/L: safe for most procedures
- 50–100 ×10⁹/L: mild bleeding risk
- <50 ×10⁹/L: bleeding with trauma/surgery
- <20 ×10⁹/L: high risk of spontaneous bleeding
- <10 ×10⁹/L: medical emergency
Reference Intervals
Adults
- 150 – 400 ×10⁹/L
(= 150–400 K/µL)
Newborns
- 150 – 450 ×10⁹/L
Pregnancy
- Mild decrease is common (gestational thrombocytopenia).
Critical Values
- < 10 ×10⁹/L → risk of intracranial hemorrhage
- > 1000 ×10⁹/L → thrombosis / bleeding paradox (MPNs)
Diagnostic Uses
1. Bleeding Disorders
Evaluate thrombocytopenia, ITP, DIC, liver disease.
2. Thrombosis Risk
High levels in MPNs or inflammation.
3. Chemotherapy Monitoring
Platelets fall earliest in marrow suppression.
4. Pre-operative Assessment
Ensure safe levels before procedures.
5. Infections & Inflammation
Platelet elevation is part of the acute phase response.
6. Splenic Disorders
Splenomegaly → low
Splenectomy → high
Analytical Notes
- Automated CBC counters; confirm low counts with manual smear
- Platelet clumping in EDTA can cause pseudothrombocytopenia
- Repeat with citrate tube if platelet clumps seen
- Cold agglutinins may falsely lower counts
- Large platelets (MPV high) seen in ITP & MPNs
Clinical Pearls
- Always correlate platelet count with MPV (size indicates production).
- EDTA-induced clumping can mimic thrombocytopenia - always rule out.
- In CKD, mild thrombocytopenia is common but function also impaired.
- Pregnancy thrombocytopenia is often benign unless <80 ×10⁹/L.
- Iron deficiency commonly causes reactive thrombocytosis.
- High platelets do NOT always mean increased clotting - MPNs cause paradoxical bleeding.
Interesting Fact
Platelets contain no nucleus, but carry RNA and mitochondria, allowing them to synthesize proteins and participate in immune functions beyond coagulation.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Hematology
- World Health Organization (WHO) Hematology Standards
- Mayo Clinic Laboratories - Platelet Count
- ARUP Consult - CBC Interpretation
- American Society of Hematology (ASH)
- MedlinePlus / NIH - Platelet Count Test