Can H. pylori Cause Elevated White Blood Cell Count?
Yes, H. pylori infection is independently associated with elevated white blood cell (WBC) count, though the increase is typically modest and reflects the chronic inflammatory response to the infection rather than acute bacterial infection.
Evidence for the Association
The relationship between H. pylori and leukocytosis is supported by both recent research and clinical observations:
A 2024 cross-sectional study of 864 patients demonstrated that H. pylori-positive individuals had significantly higher WBC counts compared to H. pylori-negative individuals 1. The study found that the prevalence of H. pylori infection increased progressively across WBC count quartiles, from 38.89% in the lowest quartile to 54.67% in the highest quartile 1.
H. pylori infection showed an independent positive correlation with WBC count (β=0.398,95% CI 0.170-0.625, p<0.001), even after adjusting for other variables 1. This indicates that the infection itself contributes to the elevated WBC count.
The effect varies with infection severity: The relationship between H. pylori bacterial load (measured by disintegration per minute in urea breath testing) and WBC count is non-linear, with different effects at different stages of infection 1. This suggests distinct immunological responses depending on the chronicity and intensity of infection.
Specific Leukocyte Changes
The elevation in WBC count involves multiple cell types:
Total leukocyte count, lymphocytes, and basophils are significantly increased in H. pylori-positive patients 2. The presence of basophilia suggests involvement of allergic mechanisms in H. pylori gastritis 2.
Platelet counts are also elevated in H. pylori-positive individuals 1, reflecting the systemic inflammatory response.
The total WBC count correlates with the severity of gastric mucosal inflammation, specifically with the numbers of neutrophils, eosinophils, and mononuclear cells in the gastric mucosa 2.
Clinical Context and Interpretation
While H. pylori can cause leukocytosis, it's important to understand the clinical context:
The WBC elevation is typically mild to moderate and reflects chronic inflammation rather than acute infection 1, 2. This is consistent with H. pylori causing chronic, persistent inflammation of the gastric mucosa 3.
H. pylori is recognized for multiple hematologic manifestations beyond leukocytosis, including iron-deficiency anemia, idiopathic thrombocytopenic purpura (ITP), and vitamin B12 deficiency 4, 5. These are well-established associations included in international consensus guidelines 4.
Severe leukocytosis (>70,000/μL) is NOT typical of H. pylori infection itself but may indicate complications of treatment, such as Clostridioides difficile colitis following eradication therapy 6.
Common Pitfalls to Avoid
Do not attribute marked leukocytosis (WBC >15,000-20,000/μL) solely to H. pylori infection without investigating other causes, as the typical elevation is modest 1, 2.
Consider that H. pylori testing may be indicated in patients with unexplained hematologic abnormalities, particularly thrombocytopenia or iron-deficiency anemia, as these have stronger evidence-based associations 4, 7.
Remember that the immune response to H. pylori involves both local gastric mucosal inflammation and systemic effects 2, which explains why peripheral blood changes occur.
Be aware that phagocytes may be relatively ineffective at eliminating H. pylori 8, contributing to the chronic nature of the infection and sustained inflammatory response.