The relationship between hematological parameters such as eosinophil-basophil levels, eosinophil-to-basophil ratio, monocyte-to-basophil ratio, and the coronary slow flow phenomenon.

Coronary slow flow phenomenon (CSFP) is characterized by delayed coronary artery filling in the absence of significant obstructive coronary artery disease. It typically presents with angina-like chest pain and is defined by delayed opacification of the coronary arteries despite the absence of obstructive lesions. Although the pathophysiology of CSFP remains poorly understood, microvascular dysfunction, endothelial impairment, and systemic inflammation have been proposed as contributing factors. Hematological parameters, such as eosinophil and basophil counts, along with the eosinophil-to-basophil ratio (EBR) and monocyte-to-basophil ratio (MBR), have emerged as potential indicators of inflammation and cardiovascular pathology. This study aimed to investigate the association between these hematological markers and CSFP to enhance understanding and guide the development of diagnostic and therapeutic strategies. In this retrospective study, eosinophil, basophil, and monocyte counts, as well as derived ratios (EBR and MBR), were analyzed in 233 patients with CSFP and 229 controls who underwent coronary angiography but had normal coronary arteries. Blood samples were processed using an automated hematology analyzer. Group comparisons were performed using the independent samples t-test and Mann-Whitney U test (P < .05). Spearman correlation and logistic regression analyses were conducted to assess associations among variables. There was no statistically significant difference in the median age between the CSFP group (56.0 [IQR: 15.0]) and the control group (57.0 [IQR: 15.0]; P = .905). The CSFP group consisted predominantly of males (161 males, 72 females), whereas the control group had a higher proportion of females (152 females, 77 males), with a statistically significant difference in sex distribution (P < .001). Patients with CSFP exhibited significantly higher monocyte counts (P < .001), eosinophil counts (P = .012), EBR (P = .010), and MBR (P = .008) than controls. This study demonstrated significant differences in hematological parameters between patients with CSFP and controls. These findings suggest that specific hematological indices, particularly immune cell ratios, could serve as accessible, cost-effective biomarkers for CSFP. Further studies are needed to clarify their mechanistic roles and therapeutic relevance.