Does a thrombocytosis (platelet count of 607) in a patient with ulcerative colitis, currently on prednisone, indicate ongoing inflammation?

Thrombocytosis in Ulcerative Colitis: Interpretation and Clinical Significance

Yes, a platelet count of 607 × 10⁹/L in a patient with ulcerative colitis indicates ongoing chronic inflammatory response, though it is not specific enough to guide treatment decisions on its own. 1

Understanding Thrombocytosis as an Inflammatory Marker

• Thrombocytosis (platelet count >450 × 10⁹/L) is a recognized manifestation of chronic inflammatory response in ulcerative colitis, appearing as part of the acute phase reaction to ongoing intestinal inflammation. 1

• The European Crohn's and Colitis Organisation guidelines explicitly state that full blood count may reveal thrombocytosis as a result of the chronic inflammatory response in UC patients. 1

• However, thrombocytosis alone cannot distinguish between active UC and other causes of inflammation, and it is not specific enough to differentiate UC from infectious or other causes of colitis. 1

Clinical Context and Limitations

• While your platelet count of 607 suggests ongoing inflammation, laboratory markers of chronic inflammation may be normal in mild or moderate UC, so the absence of other inflammatory markers doesn't rule out active disease. 1

• The presence of thrombocytosis should prompt assessment of other inflammatory markers, particularly CRP, which broadly correlates with clinical severity in UC (except in proctitis). 1

• In patients with severe clinical activity, elevated CRP is generally associated with elevated ESR, anemia, and hypoalbuminemia, which together provide a more complete picture of disease activity. 1

Prednisone Effect Consideration

• Corticosteroids like prednisone can themselves cause thrombocytosis independent of disease activity, which complicates interpretation in your case. This is a critical pitfall when evaluating platelet counts in patients on steroid therapy.

• The thrombocytosis may represent: (1) ongoing UC inflammation despite prednisone, (2) a medication effect from prednisone itself, or (3) both factors combined.

Superior Biomarkers for Assessing Disease Activity

Rather than relying on platelet count, fecal calprotectin is the preferred biomarker for assessing intestinal inflammation in UC:

• Fecal calprotectin >150 μg/g in patients with moderate to severe symptoms has only a 4.6% false positive rate, meaning 95.4% of such patients have true moderate-to-severe endoscopic inflammation. 1, 2

• In symptomatic patients, fecal calprotectin >150 μg/g reliably suggests moderate to severe endoscopic inflammation, potentially obviating the need for immediate endoscopic assessment. 1

• CRP has lower sensitivity (63%) and specificity (77%) compared to fecal calprotectin for detecting endoscopic inflammation, making it a less reliable marker. 1

Recommended Clinical Approach

Given your thrombocytosis and current prednisone therapy, the following algorithm should guide management:

1. Measure fecal calprotectin immediately to objectively assess intestinal inflammation independent of steroid effects. 1, 2

2. If fecal calprotectin >150 μg/g with moderate-to-severe symptoms (frequent rectal bleeding, significantly increased stool frequency): Consider empiric treatment adjustment without requiring endoscopy first. 1, 2

3. If fecal calprotectin >150 μg/g with mild symptoms (infrequent rectal bleeding, mildly increased stool frequency): Proceed with endoscopic assessment before treatment adjustment. 1

4. If fecal calprotectin <150 μg/g in symptomatic remission: This reliably rules out active inflammation, and the thrombocytosis is more likely medication-related. 1, 2

Thrombotic Risk Consideration

• Patients with severe UC and thrombocytosis have increased risk of venous thromboembolism, requiring screening and potentially prophylactic anticoagulation during acute flares. 3

• Platelets play a role in amplifying inflammatory and immune responses in chronic inflammation, creating a bidirectional relationship between thrombocytosis and UC activity. 3

• Biologic therapies (particularly infliximab) significantly reduce platelet aggregability, which may reduce cardiovascular and thrombotic risk beyond their anti-inflammatory effects. 4

Key Clinical Pitfalls to Avoid

• Do not use platelet count alone to guide UC treatment decisions – it lacks specificity and is confounded by corticosteroid therapy. 1

• Do not assume thrombocytosis resolution means disease control – use objective measures like fecal calprotectin or endoscopy to confirm mucosal healing. 1, 2

• Do not ignore persistent thrombocytosis after achieving clinical remission – consider thrombotic risk assessment, especially if platelet count remains >600 × 10⁹/L. 3