Interleukin-18: Interleukin-10 ratio and in-hospital adverse events in patients with acute coronary syndrome

Atherosclerosis 182 (2005) 135–143

Interleukin-18: Interleukin-10 ratio and in-hospital adverse events in patients with acute coronary syndrome Georgios K. Chalikias a , Dimitrios N. Tziakas a,∗ , Juan Carlos Kaski c , Eleni I. Hatzinikolaou a , Dimitrios A. Stakos a , Ioannis K. Tentes b , Alexandros Kortsaris b , Dimitrios I. Hatseras a a

c

University Cardiology Clinic, Democritus University of Thrace, Voulgaroktonou 23, 68100 Alexandroupolis, Greece b Department of Biochemistry, Democritus University of Thrace, Alexandroupolis, Greece Coronary Artery Disease Research Unit, Department of Cardiological Sciences, St George’s Hospital Medical School, London, UK Received 7 November 2004; received in revised form 26 January 2005; accepted 2 February 2005 Available online 26 February 2005

Abstract Introduction: Inflammatory mechanisms contribute to the development of acute coronary syndromes (ACS), and it has been suggested that an imbalance between pro- and anti-inflammatory responses may be an important determinant of recurrent cardiac events in this setting. Both increased serum levels of interleukin (IL)-18 and reduced concentrations of IL-10 have been shown to have prognostic significance in ACS. We sought to assess whether the ratio of serum IL-18/IL-10 levels has higher positive predictive value than the individual measurement of IL-10 and IL-18 in patients admitted to hospital with ACS. Methods: We recruited 107 consecutive patients (79 men, mean age 65 ± 12 years) with ACS (41 STEMI, 39 NSTEMI and 27 UA). The composite of cardiac death, recurrence of unstable angina, re-infarction, life threatening arrhythmias, and urgent revascularization during hospitalization was the pre-specified study end-point. We assessed independent predictors of the combined end-point using multiple logistic regression analysis. Serum IL-10 and IL-18 levels were measured at study entry using commercially available ELISAs. Results: During hospitalization 44 patients (41%) had events and 63 (59%) had no events. Significantly higher odd ratios were found for IL-18/IL-10 ratio (1.74 95% CI 1.09–2.78) compared to individual IL-18 (1.46 95% CI 0.93–2.27) and 1/IL-10 (1.63 95% CI 1.04–2.56) measurements. Conclusion: Serum IL-18/IL-10 ratio is an independent predictor of in-hospital adverse events in patients with ACS. Our study strongly endorses the notion that an imbalance between pro and anti-inflammatory forces predisposes to plaque disruption and recurrent cardiovascular events. © 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Acute coronary syndrome; Inflammation; Interleukin-18; Interleukin-10; ACS prognosis

1. Introduction Acute coronary syndromes (ACS) are often the clinical manifestation of a ruptured, fissured or eroded atherosclerotic plaque [1]. Atherosclerotic plaque instability leading to adverse events is the consequence of a complex inflammatory response of the vessel wall that involves the activa∗

Corresponding author. Tel.: +30 25510 35596; fax: +30 25510 35596. E-mail address: [email protected] (D.N. Tziakas).

0021-9150/$ – see front matter © 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.atherosclerosis.2005.02.002

tion of macrophages and T cells and the production of proinflammatory cytokine [2]. Pro-inflammatory cytokines such as interleukin-6 (IL-6) and interleukin-18 (IL-18) are elevated in patients with ACS and have been shown to play a role in plaque instability [3,4]. In contrast, anti-inflammatory cytokine levels such as those of interleukin-10 (IL-10) have been shown to be reduced in patients with ACS compared to stable angina patients [5] and to have a protective role in atherosclerosis [6,7]. Current evidence supports the hypothesis that ACS are associated with the development of

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cell-mediated cytotoxicity, involving specific T cells and nonantigen specific NK cells [8]. The activity of such cells is under the control of Th1 immune response, and IL-18 has been shown to be a strong co-factor in this process [9]. IL10, on the other hand, is associated with the development of the Th2 immune response, which has been shown to inhibit pro-atherogenic processes via several mechanisms [10]. It is therefore conceivable that the balance between Th1 and Th2 responses within a given individual is of crucial importance regarding the development of atherosclerosis and acute coronary events. Elevation of serum levels of proinflammatory cytokines such as IL-18 has been shown to predict unfavourable outcomes in patients with ACS [11], whereas elevation of serum levels of Th2 response cytokines such as IL-10, has been reported to be associated with a good prognosis in patients with unstable coronary artery disease [12]. Currently, little if any data exist regarding the prognostic significance of combined measurements of serum pro- and anti-inflammatory cytokine levels in patients presenting with an ACS. We therefore sought to assess whether serum IL-18/IL-10 ratio provides short term prognostic information in patients with ACS.

2. Methods 2.1. Patients This study enrolled 107 patients who were admitted to the Coronary Care Unit of the University Hospital of Democritus University of Thrace with a diagnosis of ACS. Myocardial infarction (MI) was diagnosed in the presence of prolonged (>20 min) chest discomfort in the last 24 h with ST segment changes suggestive of myocardial ischemia or necrosis on the standard 12-lead electrocardiogram (ECG), and increased serum markers of myocardial damage measured on at least two occasions during the first 24 h after the index event (>2fold increase over the upper normal range required for creatine kinase-myocardial fraction (CK-MB) and Troponin T). MI patients were considered to have ST segment elevation MI (STEMI) in the presence of ≥0.2 mV ST segment elevation at the J point in two or more contiguous ECG leads. Non-ST segment elevation MI (NSTEMI) was diagnosed in the presence of new ST segment depression (≥0.1 mV) or T wave inversion (≥0.3 mV) in two or more contiguous leads [13,14]. Patients with equivocal or uninterpretable ECGs (i.e. left bundle branch block, paced rhythm or persistent ST segment elevation after a previous MI) were not included in the study. UA was defined as anginal pain at rest fulfilling Braunwald’s IIIb criteria with transient significant ischemic ST segment or T wave changes, or both, without evidence of myocardial damage [15]. All patients underwent routine risk stratification using TIMI risk score for STEMI [16] and UA/NSTEMI [17] and the Killip classification [18].

The study was approved by the Hospital’s Ethics Committee and all patients gave written informed consent prior to study entry. All patients were monitored for in-hospital adverse cardiac events. The primary end-point of the study was the composite of cardiac death, recurrent ischemia or angina, re-infarction, life threatening arrhythmias and urgent revascularization during hospitalization. Cardiac death was defined as sudden unexplained death, death from fatal myocardial infarction or death from possible myocardial ischemia. Re-infarction was defined as prolonged angina accompanied by new ECG changes and ≥50% of previous value of CK-MB or Troponin T. Recurrent ischemia/angina was defined as rest angina with new ECG abnormalities but without elevation of CK-MB or Troponin T levels. Life threatening arrhythmias were defined as rhythm disturbances leading to hemodynamic instability that required immediate electrical or pharmacological intervention. Urgent revascularization was defined as an episode of recurrent angina prompting the performance of percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) on the index hospitalization. The present study did not include patients with a history of hematological, neoplastic, renal, liver or thyroid disease or patients receiving treatment with anti-inflammatory drugs. Furthermore patients with infectious or autoimmune diseases, familial hyperlipidemia, or those undergoing surgical procedures in the preceding 3 months were excluded from the study. 2.2. Biochemical data In all patients peripheral blood samples were drawn within 1 h from admission. After centrifugation at 3000 rpm for 10 min, serum samples were frozen and stored at −70 ◦ C until biochemical assessment. Sandwich enzyme immunoassay was performed for measuring concentrations of serum IL-10 using “Quantikine HS human IL-10, R&D Systems Inc., Minneapolis, USA” [5] commercial kits with monoclonal antibodies, with a minimum detectable concentration of <0.5 pg/ml. The intra- and inter-assay precision of the method were 8.5 and 15.6%, respectively. Sandwich enzyme immunoassay was performed for measuring concentrations of serum IL-18 using “MBL Medical and Biological Laboratories Co. Ltd., Nagoya, Japan” [4] commercial kits with monoclonal antibodies, with a minimum detectable concentration of 12.5 pg/ml. The intra-assay precision and inter-assay precision of the method were 5.61 and 10.1%, respectively. C-reactive protein (CRP) was measured using a nephelometric method using “Dade Behring, Marburg, Germany” [19] commercial kits with a lower detection limit of 0.1 mg/dl. All other biochemistry measurements were carried out by our biochemistry department using standard methods.

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3. Statistical analysis All values are expressed as mean values with 95% confidence intervals or median values and interquartile ranges. Patients were divided in two groups according to the presence or absence of one or more adverse events during hospitalization (combined end point of cardiac death, recurrent ischemia, re-infarction, life threatening arrhythmias and urgent revascularization). Unpaired Student’s t-test was used to evaluate differences in continuous variables between the two groups, whereas comparisons between categorical variables were performed by chi-square test or Fischer’s exact test when required. The Kolmogorov–Smirnof test was used to examine the normality of the variables distribution. IL-10 levels, IL-18 levels and the ratio IL-18/IL-10 were not normally distributed therefore were transformed logarithmically as required to approach normal distribution and obtain equal variances. We assessed independent predictors of the combined end-point using multiple logistic regression analysis with independent variables being those with p < 0.05 in a univariate logistic regression analysis. In these analysis inflammatory markers were considered in quartiles. Correlation analysis between variables of the study was made by means of Spearman’s correlation coefficient r for continuous variables with non-normal distribution and Kendal’s correlation coefficient tau-b for nominal/ordinal variables. A p value <0.05 was considered statistically significant.

4. Results Forty-four patients (41%) had one or more adverse events during hospital admission and 63 (59%) were event free during hospitalization. During the study, six cardiac deaths occurred, 26 patients had recurrent episodes of myocardial ischemia and five had a re-infarction. Furthermore, in 13 patients life threatening arrhythmias were documented and nine patients were referred for urgent revascularization procedures. Overall, in patients with ACS baseline levels for IL-10 were 4.7 pg/ml (IQ 1.9 pg/ml), for IL-18 were 236.2 pg/ml (IQ 195 pg/ml), for 1/IL-10 were 0.22 pg/ml−1 (IQ 0.09 pg/ml−1 ) and for IL-18/IL-10 ratio were 51.51 (IQ 51.23). Baseline demographic, clinical and treatment data are presented in Table 1. No differences were found between patients with adverse in-hospital events and those without, with the exception of higher TIMI risk scores in patients with adverse in-hospital events and a history of coronary artery disease. IL-18, ratio IL-18/IL-10, CRP, and fibrinogen levels were significantly higher among patients with adverse events. Conversely IL-10 levels were significantly higher among those who did not have adverse events during admission to hospital (Table 1 and Fig. 1). Correlation analysis among IL-10, 1/IL-10, IL-18, ratio IL-18/IL-10 and presence or absence of in-hospital

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adverse events showed a linear association between number of adverse events and quartiles of IL-10 (Kendal’s tau-b = −0.197, p = 0.022), quartiles of 1/IL-10 (Kendal’s tau-b = 0.193, p = 0.024), quartiles of IL-18 (Kendal’s taub = 0.192, p = 0.025) and quartiles of ratio IL-18/IL-10 (Kendal’s tau-b = 0.255, p = 0.002) (Fig. 2). We observed more adverse events in the higher quartiles of 1/IL-10, IL-18 and IL-18/IL-10 ratio compared to the lower quartiles. Conversely more adverse events occurred in patients in the lower quartiles of IL-10 compared to those in the higher quartiles. After checking for co-linearity, we performed logistic regression analysis for each continuous and categorical variables that on univariate analysis were shown to have a significant difference or a trend to a difference between patients with adverse in-hospital events and patients without (Table 2). We also performed multivariate logistic regression analysis on IL-10, 1/IL-10, IL-18 and ratio IL-18/IL-10 adjusted for all the continuous and categorical variables that were shown to predict adverse events on univariate logistic regression analysis (Table 3). We observed higher odd ratios for the combined end-point for IL-18/IL-10 ratio compared to odd ratios for 1/IL-10 and IL-18 in unadjusted analysis. Furthermore IL-18/IL-10 ratio remained an independent significant predictor of in-hospital adverse events with higher odd ratios compared to 1/IL-10 and IL-18, when other predictors of in-hospital mortality and morbidity, were entered into the analysis (Fig. 3). We also performed logistic regression analysis in subgroups of patients who were considered to be at low, and high risk for in hospital mortality based on bio markers such as CRP, fibrinogen and Troponin T. Arbitrarily we used the median value of the above risk markers as a cut off value. Logistic regression analysis in both unadjusted and adjusted models showed the ratio IL-18/IL-10 to be a predictor of adverse events in the low risk patient subgroup (Table 4). Furthermore IL-18/IL-10 ratio added predictive information in patients who were at a high risk, as assessed by established biomarkers, and after adjustment for confounding prediction variables (Table 5). Finally, we analysed subgroups of patients who were considered to be at low and high risk for in hospital adverse events using novel markers such as IL-10 and IL-18. We used the median value of the risk markers as a cut off value. Logistic regression analysis in the high risk subgroup (IL-18 levels >236.2 pg/ml median value of the study population) showed that both IL-10 (OR 0.48 95% CI 0.28–0.85, p = 0.012) and IL-18/IL-10 (OR 3.29 95% CI 1.47–7.35, p = 0.004) were predictors of adverse cardiac events. In contrast, IL-18 levels failed to further stratify patients considered to be at low risk based on the presence of high levels of IL-10. Logistic regression analysis in the low risk subgroup of patients (IL-10 levels >4.7 pg/ml median value of the study population) showed that neither IL-18 (OR 1.16 95% CI 0.65–2.06, p = 0.615) nor IL-18/IL-10 (OR 1.15 95% CI 0.66–2, p = 0.608) were

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Table 1 Baseline characteristics of patients in both groups Variable

Patients with adverse events (n = 44)

Patients with no adverse events (n = 63)

p

Age (years) Lipid profile Total cholesterol (mg/dl) LDL cholesterol (mg/dl) HDL cholesterol (mg/dl) Triglycerides (mg/dl)

66 (62–69)

66 (62–68)

0.728

210 (196–224) 138 (127–150) 44 (41–47) 153 (131–174)

211 (199–224) 134 (124–145) 43 (41–46) 167 (147–188)

0.907 0.604 0.804 0.347

Risk factors of CAD Gender Male Female Hypertension Diabetes Dyslipidaemia Smoking Family history of CAD Prior history of CAD

36 (82%) 8 (18%) 26 (59%) 14 (32%) 22 (50%) 20 (45%) 12 (27%) 28 (64%)

43 (68%) 20 (32%) 43 (68%) 18 (29%) 33 (52%) 21 (33%) 8 (13%) 25 (40%)

0.221 0.831 0.846 0.230 0.078 0.019a

Treatment Aspirin Clopidogrel Lipid lowering agent B-blocker ACE inhibitor

17 (39%) 5 (11%) 13 (29%) 11 (25%) 12 (27%)

19 (30%) 7 (11%) 19 (30%) 14 (22%) 20 (32%)

0.409 1 1 0.818 0.672

Admission to hospital with STEMI NSTEMI UA

19 (43%) 12 (27%) 13 (29%)

22 (35%) 27 (43%) 14 (22%)

Hospital treatment. Thrombolysis IIb/IIIa GP antagonists LMW Heparin

12 (27%) 13 (29%) 44 (100%)

16 (25%) 9 (14%) 63 (100%)

0.126

0.254

0.827 0.087 1

Risk stratification markers Killip class stratification Killip class 1 Killip class 2–4 TIMI risk score stratification TIMI risk score 0–5 TIMI risk score >6

33 (75%) 11 (25%)

52 (82%) 11 (17%)

22 (58%) 16 (42%)

48 (83%) 10 (17%)

Hospitalization days

9 (3)

8 (2)

0.034b

Biomarkers. IL-10 (pg/ml) 1/IL-10 (pg/ml−1 ) IL-18 (pg/ml) Ratio IL-18/IL-10 CRP (mg/dl) Fibrinogen (mg/dl) Troponin T (ng/ml)

4.33 (2.24) 0.38 (0.18) 285 (286) 65.14 (73.45) 1.78 (1.36) 393.35 (18.28) 0.5 (0.69)

5.14 (2.07) 0.25 (0.08) 212 (159.5) 46.1 (31.53) 0.96 (0.04) 385.31 (0.04) 0.4 (0.59)

0.028b 0.037b 0.011b 0.002b <0.001b 0.001b 0.559

0.466

0.01a

Values are expressed as means and 95% CIs for quantitative variables with normal distribution, as medians and interquartile ranges for quantitative variables with non-normal distribution, and as number of patients and % for qualitative variables. a For chi-square test. b for Mann–Whittney U test.

predictors of adverse cardiac events. However, both IL-18 and IL-18/IL-10 ratio were useful to further stratify patients at high risk (low IL-10 levels). Logistic regression analysis showed that both IL-18 (OR 2.27 95% CI 1.3–3.93, p = 0.004) and IL-18/IL-10 (OR 2.14 95% CI 1.15–3.96, p = 0.016) were predictors of adverse cardiac events in patients with IL10 levels <4.7 pg/ml median value of the study population.

5. Discussion Our study showed for the first time that serum ratio of IL-18/IL-10 levels is an independent predictor of short-term prognosis in patients with ACS. The study also showed that serum ratio of IL-18/IL-10 adds predictive information regarding in-hospital morbidity and mortality over and above

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Fig. 1. Patients with in-hospital adverse events had higher levels of pro-inflammatory markers such as IL-18, 1/IL10 and ratio IL-18/IL-10. In contrast, patients without in-hospital adverse events had higher levels of the anti-inflammatory cytokine IL-10.

Table 2 Logistic regression analysis of continuous and categorical variables that on univariate analysis were shown to have a significant difference or a trend to a difference Variable

OR

95% CI

p

IL-10 1/IL-10 IL-18 IL-18/IL-10 CRP Fibrinogen Hospitalization days Time to treatment TIMI risk score Prior history of CAD Family history of CAD Use of IIb/IIIa GP antagonists

0.66 1.48 1.48 1.71 2.15 1.75 1.27 0.89 1.24 2.66 2.57 2.51

0.46–0.96 1.03–2.13 1.03–2.13 1.17–2.47 1.43–3.23 1.18–2.6 1.05–1.55 0.81–0.98 1.01–1.53 1.2–5.89 0.95–6.97 0.96–6.55

0.028 0.031 0.031 0.005 <0.001 0.005 0.014 0.026 0.04 0.016 0.062 0.059

that of serum IL-18 and 1/IL-10 levels. In addition, the IL18/IL-10 ratio remained a significant predictor of prognosis in both patients at low and high risk (as assessed by conventional risk markers). However, when IL-18 or IL-10 were used to stratify patients as low or high risk, the added predictive value of IL-10, IL-18 and IL-18/IL-10 ratio was restricted to patients at high risk. These results are in agreement with previous studies that have demonstrated that elevated IL-10 serum levels are associated with a significantly improved outcome of patients with acute coronary syndromes [12], and results that indicated that IL-18 provides powerful information for future fatal cardiovascular events in patients with unstable coronary artery disease [11]. Consistent with findings from studies of Heeschen et al. [12] and Blankenberg et al. [11], our study did not show any correlation between pro- or anti-inflammatory cytokines and markers of myocardial necrosis such as Troponin T. Thus extent of myocardial necrosis seems not to have influence our results.

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Fig. 2. More in-hospital adverse events (combination of cardiac death, recurrent ischemia or angina, re-infarction, life threatening arrhythmias and urgent revascularization) were observed in the highest quartiles of IL-18, 1/IL-10 and IL-18/IL-10 ratio. On the contrary more in-hospital adverse events were observed in the lowest quartiles of IL-10.

Interleukin-10 has anti-inflammatory properties including inhibition of the pro-inflammatory transcription factor nuclear factor kappa B leading to suppressed cytokine production [20], reduced matrix metalloproteinase production [21], reduced tissue factor expression [22] and promotion of the phenotypic switch of lymphocytes to Th2 phenotype [23]. IL-10 expression has been demonstrated in advanced human atherosclerotic plaques with high levels of expression associated with significantly decreased cell death and iNOS ex-

pression again suggesting a protective anti-atherogenic role [24]. Interleukin-18 on the other hand may aggravate the pro-inflammatory response through interferon-gamma (IFN␥) production [25], increased expression of cell adhesion molecules [26] and pro-inflammatory mediators particularly tumour necrosis factor ␣, interleukin-1␤ [27], as well as to promote the development of T helper-1 (Th1) responses [28]. Moreover IL-18 has been identified in human atherosclerotic

Table 3 Multivariate logistic regression analysis incorporating assumed variables, unadjusted, lipid adjusted, and fully adjusted Variable

IL-10 1/IL-10 IL-18 IL-18/IL-10

Unadjusted

Lipid adjusted

Fully adjusted

OR

95% CI

p

OR

95% CI

p

OR

95% CI

p

0.66 1.48 1.48 1.71

0.46–0.96 1.03–2.13 1.03–2.13 1.17–2.47

0.028 0.031 0.031 0.005

0.69 1.42 1.5 1.69

0.48–1.03 0.98–2.06 1.04–2.16 1.15–2.47

0.052 0.061 0.029 0.007

0.56 1.63 1.46 1.74

0.35–0.88 1.04–2.56 0.93–2.27 1.09–2.78

0.014 0.033 0.09 0.02

Lipid adjusted model additionally controlled for total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides. Fully adjusted model additionally controlled for CRP levels, TIMI risk score, fibrinogen levels, history of prior CAD, hospitalization days and time to treatment. Inflammatory markers were analyzed as ordinal variables in quartiles.

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Table 4 Low risk patients according to classical risk markers, subgroup logistic regression analysis of IL-10, 1/IL-10, IL-18 and ratio IL-18/IL-10 Low risk subgroup

Variable

Unadjusted

Fully adjusted

OR

95% CI

p

OR

95% CI

p

Low (<0,97mg/dl) CRP levels

IL-10 1/IL-10 IL-18 IL-18/IL-10 IL-10

0.46 1.92 2.02 3.04 0.70

0.23–0.92 0.99–3.72 1.02–4.01 1.37–6.74 0.39–1.24

0.027 0.051 0.043 0.006 0.226

0.81 0.75 1.73 2.82 0.54

0.20–3.31 0.20–2.87 0.85–3.49 1.18–6.75 0.26–1.10

0.774 0.681 0.128 0.02 0.092

Low (<0.5 ng/ml) Troponin T levels

1/IL-10 IL-18 IL-18/IL-10 IL-10

1.41 1.75 1.84 0.32

0.79–2.48 1.02–3.02 1.06–3.21 0.13–0.75

0.241 0.044 0.029 0.009

1.83 1.70 2.12 0.30

0.91–3.71 0.96–3.02 1.13–3.99 0.09–1.04

0.092 0.069 0.019 0.059

Low (<385.32 mg/dl) fibrinogen levels

1/IL-10 IL-18 IL-18/IL-10 IL-10

3.15 1.49 2.03 0.63

1.33–7.44 0.83–2.69 1.06–3.87 0.41–0.98

0.009 0.178 0.031 0.043

3.18 1.79 2.32 0.46

0.91–11.13 0.77–4.18 0.90–5.99 0.26–0.82

0.070 0.176 0.081 0.009

Low (<6) TIMI risk scores

1/IL-10 IL-18 IL-18/IL-10

1.54 1.37 1.62

0.99–2.39 0.90–2.09 1.03–2.54

0.057 0.137 0.034

1.93 1.39 1.72

1.09–3.39 0.86–2.26 1.01–2.92

0.022 0.175 0.046

Fully adjusted model controlled for lipid levels, CRP levels, TIMI risk score, fibrinogen levels, history of prior CAD, hospitalization days and time to treatment. Inflammatory markers were analyzed as ordinal variables in quartiles.

lesions with significantly higher levels of IL-18 mRNA in unstable plaques [29]. One of the limitations of our study is that it was not powered to analyze ORs for each one of the four quartiles of the variables under investigation. Even though linear association analysis between the number of adverse events and quartiles for IL-18/IL-10 ratio showed strong and positive associations (Fig. 2) ORs of 1/IL-10 were more consistent across the four quartiles compared to ORs IL-18/IL-10. Further ad hoc studies are needed to elucidate what is the true predictive ability of the studied variables (across the four quartiles).

Two studies have previously shown that in patients with unstable coronary artery disease there is an imbalance between pro-inflammatory and anti-inflammatory cytokines [30,31]. However the present study is the first study to show an association between pro- and anti-inflammatory cytokines imbalance and short term prognosis in patients with ACS. The results of the present study endorse the concept that the balance between pro-inflammatory and anti-inflammatory cytokines may be an important determinant of patient outcome. The independent prognostic ability of IL-18/IL-10 ratio in our study warrants investigation in larger patient cohorts to determine its clinical usefulness. Our results also support the

Table 5 High risk patients according to classical risk markers, subgroup logistic regression analysis of IL-10, 1/IL-10, IL-18 and ratio IL-18/IL-10 High risk subgroup

Variable

Unadjusted

Fully adjusted

OR

95% CI

p

OR

95% CI

p

High (≥0.97 mg/dl) CRP levels

IL-10 1/IL-10 IL-18 IL-18/IL-10

0.69 1.50 1.23 1.51

0.46–1.04 0.99–2.27 0.82–1.86 1–2.26

0.078 0.054 0.321 0.049

0.71 1.46 1.24 1.59

0.43–1.16 0.88–2.40 0.74–2.06 0.96–2.62

0.963 0.138 0.410 0.07

High (≥0.5 ng/ml) Troponin T levels

IL-10 1/IL-10 IL-18 IL-18/IL-10

0.56 1.74 1.43 1.81

0.36–0.86 1.13–2.66 0.92–2.21 1.14–2.87

0.008 0.011 0.107 0.012

0.39 2.46 1.33 2.23

0.21–0.71 1.34–4.50 0.77–2.31 1.16–4.27

0.002 0.004 0.303 0.016

High (≥385.32 mg/dl) fibrinogen levels

IL-10 1/IL-10 IL-18 IL-18/IL-10

0.78 1.30 1.57 1.65

0.52–1.16 0.87–1.94 1.01–2.45 1.06–2.55

0.218 0.205 0.045 0.025

0.69 1.35 1.52 1.77

0.42–1.14 0.82–2.27 0.88–2.61 1.02–3.06

0.150 0.242 0.132 0.041

High (≥6) TIMI risk scores

IL-10 1/IL-10 IL-18 IL-18/IL-10

0.86 1.24 1.58 1.65

0.52–1.43 0.74–2.06 0.91–2.74 0.95–2.87

0.565 0.416 0.105 0.074

0.65 1.78 1.63 2.19

0.29–1.42 0.76–4.15 0.78–3.41 0.95–5.01

0.282 0.183 0.193 0.064

Fully adjusted model controlled for lipid levels, CRP levels, TIMI risk score, fibrinogen levels, history of prior CAD, hospitalization days and time to treatment. Inflammatory markers were analyzed as ordinal variables in quartiles.

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Fig. 3. Higher odd ratios for the combined end point of cardiac death, recurrence of angina, re-infarction, life threatening arrhythmias and urgent revascularization were observed for IL-18/IL-10 compared to odd ratios for IL-18 and 1/IL-10 both in crude and adjusted analysis.

notion that therapeutic interventions to transpose the imbalance in favor of anti-inflammatory cytokines may represent a useful therapeutic strategy for stabilizing atherosclerotic plaques and improving clinical outcome after acute coronary syndromes.

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