Retinal capillary rarefaction is associated with the systemic immune-inflammatory index in patients with hypertension.

Objective: Rarefaction in capillary density is a hallmark of hypertension-mediated microvascular damage. This study aimed to assess the association between clinically accessible inflammatory markers, including the systemic immune-inflammation index (SII), and retinal capillary density, as well as other indicators of microvascular damage.

Methods: We conducted a cross-sectional analysis of data from 132 consecutive patients with established primary hypertension at the Royal Perth Hospital's tertiary hypertension clinic. All patients underwent noninvasive optical coherence tomographic angiography (OCT-A) for the assessment of retinal capillary density in the foveal region (CDF) and blood sampling for inflammatory markers. We examined the association of the SII - calculated as the product of the neutrophil-lymphocyte ratio and platelet count - and its individual components with retinal capillary rarefaction and other markers of microvascular damage, such as the urinary albumin-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR). The results were adjusted for relevant co-variates, including age, sex, 24-h SBP, BMI, antihypertensive medications, lipid levels, and diabetes status.

Results: Retinal capillary rarefaction was associated with increased white cell count, particularly neutrophils, and the SII. Through predictive margin analysis, an optimal cut-off value of 600 x 109/l for SII was determined for median CDF of 34.1 mm2. The analysis showed a reduction in CDF of 1.3 mm2 for every 250 x 109/l increase in SII. Additionally, higher SII levels (≥ 600 x 109/l) were associated with elevated high-sensitivity C-reactive protein (hs-CRP) levels and markers of microvascular damage, such as increased UACR and reduced eGFR.

Conclusion: In patients with primary hypertension, SII and related inflammatory markers were associated with retinal rarefaction and renal indices of microvascular damage. SII may serve as a useful clinical marker of microvascular damage in the retinal and renal vascular bed.