The Neutrophil-Lymphocyte Ratio and Atherosclerotic Events

Posted on by

The neutrophil-lymphocyte ratio and incident atherosclerotic events: analyses from five contemporary randomized trials.

Adamstein NH, MacFadyen JG, Rose LM, Glynn RJ, Dey AK, Libby P, Tabas IA, Mehta NN, Ridker PM.

Eur Heart J. 2021 Mar 1;42(9):896-903. [Full text]

Summary by Amit Dey

Atherosclerosis is a multifactorial disease with profoundly altered lipoprotein metabolism. Elevated LDL cholesterol (LDL-C) is implicated, as are a fairly large number of proinflammatory molecules, and various cell types in the vascular wall but also in the peripheral circulation. Circulating white blood cells (WBCs) are predictive of cardiovascular diseases such as myocardial infarction and stroke. Yet there are clearly many other factors effecting WBCs such as corticosteroids, vasoactive substances, and pathological determinants such as bacterial products and complement activation. Specific WBC subtypes may be more reliable predictors of cardiovascular risk, and in particular the neutrophil–lymphocyte ratio (NLR) has shown promise in a number of different patient populations (after PCI or CABG, during ACS, or in decompensated HF), albeit in relatively small populations. In the following study, five prior studies were retrospectively analyzed to see how the NLR correlated to major adverse cardiovascular events (MACE).

Patient population and Design

Four studies were included. These are:

  1. CANTOS randomized 10,061 patients with prior myocardial infarction (MI) and a baseline high‐sensitivity CRP (hsCRP) ≥2mg/L to placebo or canakinumab in doses of 50 mg, 150 mg, or 300 mg subcutaneously once every 3 months. Subjects were followed up for a primary CV endpoint of three-point major adverse cardiovascular events (MACE), defined as the composite of non-fatal MI, non-fatal stroke, or CV death (median follow-up 3.7 years). A secondary endpoint was defined as the primary CV endpoint plus hospitalization for unstable angina requiring urgent revascularization (MACE+). 
  2. Justification for the Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) randomized 17 802 healthy patients with LDL-cholesterol (LDL-C) of less than 130 mg/dL and hsCRP ≥2.0 mg/L to 20 mg of rosuvastatin or placebo.16 The primary endpoint was the composite of MI, stroke, arterial revascularization, hospitalization for unstable angina, or CV death (median follow-up: 1.9 years). 
  3. Studies of PCSK9 Inhibition and the Reduction of Vascular Events (SPIRE) in two separate trials (SPIRE-1 and SPIRE-2) collectively randomized 27 438 patients (16 817 and 10 621 respectively) with prior CV events or at high risk to 150 mg of bococizumab subcutaneously every two weeks or placebo.17 The LDL-C cut-offs were greater than or equal to 70 mg/dL in SPIRE-1 and greater than or equal to 100 mg/dL in SPIRE-2. Patients were followed up for a primary endpoint of MACE+ (median follow-up 7 months in SPIRE-1 and 12 months in SPIRE-2). 
  4. The Cardiovascular Inflammation Reduction Trial (CIRT) randomized 4786 patients with previous MI or multi-vessel coronary disease and either type 2 diabetes or metabolic syndrome to low-dose methotrexate (15–20 mg weekly) or placebo. Patients were followed up for a primary endpoint of MACE+ (median follow-up 2.3 years).

Timing and Measurement of the ANC, ALC, and NLR

In all trials, the baseline NLR was computed from the ANC and ALC from complete blood count data obtained at randomization. In CANTOS, follow-up complete blood counts were measured at 3, 6, 9, 12, 24, 36, and 48 months, allowing us to address stability over time. In JUPITER, follow-up samples were collected only at the final visit, the timing of which varied for each participant. In SPIRE-1 and SPIRE-2, complete blood counts are available from the 14, 26, 40, and 52-week follow-up visits; the largest sample of follow-up measurements was obtained at 52 weeks. In CIRT, follow-up measurements were acquired at 4 and 8 months.

Randomized trial analyses and incident cardiovascular events

We first divided CANTOS subjects into quartiles according to baseline ANC, ALC, and NLR. Cox proportional-hazard models stratified by time since index infarction estimated the relative hazards for MACE, MACE+, all-cause mortality, and CV death across quartiles. P-values for the test of trend were calculated across these four groups. Multivariable-adjusted models included treatment group, age, sex, body mass index, hypertension, diabetes, smoking, LDL-C, and CRP. To address the ANC and ALC together, sixteen groups were formed from all combinations of ANC and ALC quartiles and hazard ratios were computed comparing each group to those in the lowest quartile of both ANC and ALC. Within CANTOS, Spearman correlation coefficients assessed the magnitude of association between the NLR, traditional CV risk factors, and inflammatory markers. 

We sought to externally validate any observations made in CANTOS in the independent JUPITER, SPIRE-1, SPIRE-2, and CIRT trials. Using parallel methods, participants in each trial were divided into quartiles of baseline NLR. Hazard ratios comparing baseline NLR quartiles for the same outcomes were computed using cox regressions. To allow for broader clinical application, this analysis was repeated dividing participants into four NLR groups (<1.5, 1.5–<2.5, 2.5–<3.5, and >3.5). These cut-off points were determined by selecting values similar to the NLR quartiles from CANTOS but rounded for ease of use and generalizability across trials. Multivariable analyses adjusted for treatment group, age, sex, hypertension, diabetes, LDL-C, and CRP. Multivariable analyses from JUPITER did not include LDL-C or diabetes (both exclusion criteria) as covariates. The CIRT models were not adjusted for diabetes, as the cox proportional-hazards model was stratified by diagnosis of diabetes vs. metabolic syndrome. 

The effect of each randomized drug (canakinumab in CANTOS, rosuvastatin in JUPITER, bococizumab in SPIRE-1 and SPIRE-2, and methotrexate in CIRT) on the NLR was determined by computing the median change in NLR from randomization to follow-up. Wilcoxon two-sample t-tests were used for comparison of two groups of numerical data, Kruskal–Wallis tests for three or more groups of numerical data, and χ2 tests for comparison of categorical data. All P-values are two-sided and all confidence intervals (CIs) computed at the 95% level. All statistical analysis was performed using SAS version 9.4. 

Results

The NLR modestly correlated with interleukin-6, C-reactive protein, and fibrinogen levels but minimally with lipids. In all five randomized trials, baseline NLR predicted incident CV events and death; the per-quartile increase in risk of MACE was 20% in CANTOS [95% confidence interval (CI) 14-25%, P < 0.0001], 31% in SPIRE-1 (95% CI 14-49%, P = 0.00007), 27% in SPIRE-2 (95% CI 12-43%, P = 0.0002), 9% in CIRT (95% CI 0.2-20%, P = 0.045), and 11% in JUPITER (95% CI 1-22%, P = 0.03). 

Effects of pharmacotherapy on ANC, ALC, and NLR

In JUPITER, SPIRE-1, and SPIRE-2, lipid-lowering therapy with rosuvastatin and bococizumab, respectively, had no significant effect on the NLR. In CIRT, methotrexate increased the NLR by 15.3% compared to 0% in the placebo group at eight months (P < 0.0001) due to a decrease in the ALC. By contrast, canakinumab significantly reduced the NLR in a dose-dependent manner; the median change in NLR at three months was −1.62%, −11.3% (P < 0.0001), −16.7% (P < 0.0001), and −23.6% (P < 0.0001) in the placebo and canakinumab 50, 150, and 300 mg groups, respectively. These changes were dependent on reductions in the ANC of 0%, −9.26%, −15%, and −21.4%. Canakinumab did not significantly influence the ALC. The dose-dependent reductions in the NLR with canakinumab mimic that for CRP and IL-6. 

Discussion

The findings indicate that the NLR (i) may represent a readily available inflammatory biomarker which predicts cardiovascular outcomes and (ii) may aid to guide anti-inflammatory treatment. How did canakinumab, which targets IL-1β, lower blood neutrophils? Neutrophils, the inflammatory granulocytes, are constantly produced in the bone marrow from which they are released into the circulation to ultimately extravasate and accumulate at sites of inflammation. IL-1β depletion could potentially impacty neutrophils via decrease in (i) production in the bone marrow; (ii) release into the blood; and/or (iii) uptake into tissues. In that light, we recently showed—in experimental myocardial infarction—that canakinumab indeed lowered blood neutrophil numbers by damping bone marrow myelopoiesis (i.e. the production of monocytes/macrophages and neutrophils). The intriguing findings will motivate future basic research studies to explore the underlying biological basis of their observations. For the time being it is ucnlear how to incorporate the NLR into clinical practice.

F: Follow upYes
R: RandomizationYes
I: Intention to treatYes
S: Similar at baselineYes
B: BlindingYes
E: Equal treatmentNo
S: Source (funding)The CANTOS, JUPITER, SPIRE, and CIRT trials were funded by Novartis, AstraZeneca, Pfizer, and the National Heart Lung and Blood Institute, respectively.
  1. Ridker PM, Everett BM, Thuren T, et al.; CANTOS Trial Group. Antiinflammatory therapy with canakinumab for atherosclerotic disease. N Engl J Med. 2017; 377:1119–1131
  2. Ridker PM, Danielson E, Fonseca FA, et al.; JUPITER Study Group. Rosuvastatin to prevent vascular events in men and women with elevated C-reactive protein. N Engl J Med. 2008 Nov 20;359(21):2195-207.
  3. Ridker PM, Revkin J, Amarenco P, et al.; SPIRE Cardiovascular Outcome Investigators. Cardiovascular Efficacy and Safety of Bococizumab in High-Risk Patients. N Engl J Med. 2017 Apr 20;376(16):1527-1539.
  4. Ridker PM, Everett BM, Pradhan A, et al.; CIRT Investigators. Low-Dose Methotrexate for the Prevention of Atherosclerotic Events. N Engl J Med. 2019 Feb 21;380(8):752-762.