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Haematology
Platelet count (PLT)
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Platelets are anucleate fragments of megakaryocytes essential for primary haemostasis. Both thrombocytopenia and thrombocytosis require a cause to be sought.
Reference interval
| Conventional (x10^3/µL) | SI (x10^9/L) | |
|---|---|---|
| Adults | 150–400 x10^3/µL | 150–400 x10^9/L |
Specimen: Whole blood (EDTA) · Conventional × 1 = SI
Causes of high values
Reactive thrombocytosis (infection, inflammation, iron deficiency, malignancy, after splenectomy, recent surgery) and essential thrombocythaemia or other myeloproliferative neoplasms.
Causes of low values
Thrombocytopenia: immune thrombocytopenia, drugs (including heparin-induced), marrow failure or infiltration, hypersplenism, DIC, TTP/HUS, pregnancy-related causes and B12 or folate deficiency. Spurious values arise from EDTA-dependent clumping.
Pre-analytical and method notes
Confirm unexpected thrombocytopenia on a blood film and in a citrate tube to exclude pseudothrombocytopenia. Reference limits vary by laboratory and ethnicity; bleeding risk depends on cause and platelet function as well as count.
References
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. Elsevier — Tier 3 (textbook)
- Loscalzo J, et al.. Harrison's Principles of Internal Medicine. McGraw-Hill, 21st edition (2022) — Tier 3 (textbook)
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