Hemoglobin–Albumin–Lymphocyte–Platelet (HALP) Score as a Novel Biomarker for Predicting Coronary Slow Flow in Patients with Angina and/or Ischemia and Nonobstructive Coronary Arteries

Background: The coronary slow flow phenomenon (CSFP) is an angiographic entity increasingly recognized in patients with angina and/or ischemia but non-obstructive coronary arteries (ANOCA/INOCA), associated with systemic inflammation, endothelial dysfunction, and microvascular abnormalities. The hemoglobin, albumin, lymphocyte, and platelet (HALP) score is a novel immunonutritional index that may reflect this multifactorial risk profile. Methods: This retrospective single-center case–control study included 122 patients with CSFP and 126 age- and sex-matched controls with normal coronary flow, all presenting with symptoms of chronic coronary syndrome. CSFP was diagnosed via corrected TIMI frame count. HALP and other inflammatory indices (NLR, PLR, SII, SIRI) were calculated from baseline laboratory values. Associations were evaluated using multivariable logistic regression, ROC analysis, and restricted cubic spline (RCS) modeling. Results: The HALP score was significantly lower in CSFP patients (mean 56.2 vs. 65.9, p < 0.001). In multivariable analysis, HALP was independently associated with CSFP (adjusted OR: 0.951; 95% CI: 0.930–0.972; p < 0.001), whereas NLR lost significance. PLR, SII, and SIRI remained independently associated. HALP showed the highest diagnostic performance (AUC: 0.698), significantly outperforming all other indices (DeLong p < 0.001). A HALP cutoff ≤ 56.4 provided 58.2% sensitivity and 77.0% specificity. RCS analysis demonstrated a significant non-linear inverse relationship (p for non-linearity = 0.034). Subgroup analyses confirmed consistent associations across age, sex, hypertension, and diabetes strata. Conclusions: The HALP score is independently associated with CSFP and outperforms traditional inflammatory indices. Its low cost and accessibility make it a promising tool for clinical risk stratification in ANOCA/INOCA patients, pending validation in multicenter prospective studies.