Yes, elevated platelet count is called thrombocytosis.
Thrombocytosis is formally defined as a platelet count ≥450 × 10⁹/L (or ≥450,000/μL) 1. This terminology is standardized and widely accepted across medical literature and clinical practice.
Understanding the Terminology
The term "thrombocytosis" specifically refers to an elevated platelet count above the normal reference range. While normal platelet counts typically range from 150-450 × 10⁹/L, thrombocytosis begins when counts exceed this upper threshold 1, 2.
Severity Classification
When thrombocytosis is present, it can be further categorized by severity:
- Mild: 450-700 × 10⁹/L
- Moderate: 700-900 × 10⁹/L
- Severe: >900 × 10⁹/L
- Extreme: >1,000 × 10⁹/L 3
Primary vs. Secondary Thrombocytosis
It's clinically important to distinguish between two main types:
Primary (Essential) Thrombocytosis represents clonal myeloproliferative disorders, most commonly essential thrombocythemia. This accounts for approximately 12-12.5% of thrombocytosis cases and is associated with higher platelet counts and increased thrombotic risk 2, 4.
Secondary (Reactive) Thrombocytosis comprises the vast majority (83-88%) of cases and results from underlying conditions including:
- Tissue injury/damage (32-42%)
- Infection (17-24%)
- Chronic inflammatory disorders (10-12%)
- Iron deficiency anemia (11%)
- Malignancy (13%) 2, 4
Clinical Significance
The distinction matters because primary thrombocytosis carries significantly higher risk of both arterial and venous thrombotic complications, while secondary thrombocytosis rarely causes vascular complications unless additional risk factors are present 4.
Note the contrast with thrombocytopenia: The opposite condition—low platelet count—is termed "thrombocytopenia" and is defined as a platelet count <150 × 10⁹/L 5.