**8. The apo-ratio in case-control CV risk studies**

#### **8.1. The INTERHEART study and risk of MI**

108 Lipoproteins – Role in Health and Diseases

the kidney and in the coronary arteries.

figures from the AMORIS study.

**7.4. The apo-ratio and risk of stroke in the AMORIS study** 

significantly stronger risk predictor than TC/HDL-C and LDL-C/HDL-C ratios.

**Figure 6.** Risk of total stroke (left) (reference 3 and 100) and ischemic stroke (right) (reference 101). Both

In a prospective follow-up study (mean observation age 11.8, range 7–17 years) based on the AMORIS population (n = 148,600). Holme et al. focused on risk of fatal and non-fatal ischaemic and haemorrhagic stroke in relation to all lipids and apos (101). Hazard ratio of

both men and women, with or without chronic kidney disease (CKD). Those with the lowest glomerular filtration rate (estimated GFR mL/min/1.73 m2, n = 5,838) had the highest aporatio. In Receiver Operator Characteristics (ROC) analysis the area under the curve (AUC) for the apo-ratio was 0.77 for men and 0.83 for women without CKD, and 0.65 and 0.74 among men and women with CKD, respectively analyses. These and other data reflect a certain advantage in the prediction of MI for the apo-ratio as compared to conventional lipids. Furthermore, the findings also indicate the presence of severe atherosclerosis both in

High LDL-C is a major risk factor for MI. However, LDL-C is rarely increased in those who suffer any type of stroke. A low HDL-C and some abnormalities in either apoB and/or apoA-I have previously been found in patients with ischaemic stroke (94-99). In 2006 Walldius et al. published the first report on risk of stroke based on the AMORIS-population (100). The relationships between different types of fatal stroke and the lipid fractions, apoB, apoA-I and the apo-ratio were examined in 98,722 men and 76,831 women followed for a mean of 10.3 years. High apoB and low apoA-I values were significantly related to risk of stroke. The odds ratio comparing the upper 10th vs. the 1st decile of the apo-ratio for all strokes adjusted for age, gender, TC and TG was 2.07 (95% CI: 1.49–2.88, p < 0.0001). The apo-ratio was linearly related to the risk of stroke although the slope was less than observed for the risk of fatal MI (**Figure 6, left)**. Low apoA-I was a common abnormality in all stroke subtypes including subarachnoidal and haemorrhagic strokes. In multivariate analyses the apo-ratio was a

> The largest case-control study which has been performed is the INTERHEART study (58) comprising 15,152 patients with a first MI compared to 14,820 subjects from 52 countries world-wide matched for age, gender, ethnicity and continent. The aim of the study was to investigate which of the nine most common risk factors had the strongest relation to risk of MI and also which of the factors was most prevalent (highest Population Attributable Risk). These factors were: lipids primarily measured as the apoB/apoA-I ratio, smoking, diabetes, hypertension, abdominal obesity, psychosocial, fruits and vegetables, exercise, and alcohol. They found that all these risk factors were statistically related to risk.

> The strongest **(Figure 7, left, (Table 1, left)** and also the most prevalent risk factor **(Table 1, right)**, was the apo-ratio both in men and women in each of the 52 countries worldwide. The apo-ratio plus smoking variables explained 70% of the entire risk which amounted to 90% for all nine risk factors taken together.

> In a subsequent paper (59) they also showed that the apo-ratio had the strongest relation to MI-risk of all other measured lipids **(Figure 7, right, top panel).** They also showed a significantly stronger relationship to MI risk for the apo-ratio than the TC/HDL-C ratio **(Figure 7, right; bottom panel).** It was also shown that apoA-I had better diagnostic power than HDL-C over a wider range of low to high values.

> Based on the findings and impact of these risk factors on risk of MI the INTERHEART Modifiable Risk Score (IHMRS) was developed based on age, the apo-ratio, smoking –

present, smoking – second hand, diabetes and hypertension with a range of points from 0-32 (102).

**Figure 7.** The INTERHEART study. Risk (Odds ratio, y-axis) versus the apoB/apoA-I ratio (left) (reference 58), and single lipids, apolipoproteins and their ratios (right) (reference 59).


**Table 1.** The INTERHEART study. Risk of myocardial infarction (AMI); Odds ratios for nine conventional risk factors (left) and Population Attributable Risk for nine conventional risk factors (right) (booth tables reprinted from reference 58).

The IHMRS was positively associated with incident MI in a large cohort of people at low risk for CV disease (12% increase in MI risk with a 1-point increase in score). The data were internally validated and the discrimination was tested (ROC c-statistic 0.69, 95% CI: 0.64-0.74) or even higher values up to 0.79 in certain global areas. Results were consistent across ethnic groups and geographic regions. A non-laboratory-based score has also been supplied. The IHMRS demonstrated clinical credibility, evidence of accuracy, and evidence of generality.

In an analysis of 15,780 patients from the INTERHEART study (103) it was shown that HbA1c was a useful diagnostic tool of risk and the levels increased with increasing apo-ratio from 0.75-0.84 for each quintile increase of HbA1c from <5.4 – >6.12% (p < 0.0001). Most of the MI patients had values in the highest HbA1c quintile. The advantage of using the aporatio in India (104), Latin America (105), Puerto Rico (106), and Africa (107) based on the INTERHEART study designs has been useful for evaluating CV risk and should be valuable in treating risk in these countries but also elsewhere in the world.

#### **8.2. The INTERSTROKE study**

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(102).

present, smoking – second hand, diabetes and hypertension with a range of points from 0-32

**Figure 7.** The INTERHEART study. Risk (Odds ratio, y-axis) versus the apoB/apoA-I ratio (left)

**Table 1.** The INTERHEART study. Risk of myocardial infarction (AMI); Odds ratios for nine

(booth tables reprinted from reference 58).

conventional risk factors (left) and Population Attributable Risk for nine conventional risk factors (right)

The IHMRS was positively associated with incident MI in a large cohort of people at low risk for CV disease (12% increase in MI risk with a 1-point increase in score). The data were internally validated and the discrimination was tested (ROC c-statistic 0.69, 95% CI: 0.64-0.74) or even higher values up to 0.79 in certain global areas. Results were consistent across ethnic groups and geographic regions. A non-laboratory-based score has also been supplied. The IHMRS demonstrated clinical credibility, evidence of accuracy, and evidence of generality.

(reference 58), and single lipids, apolipoproteins and their ratios (right) (reference 59).

The standardized INTERSTROKE case-control study was performed in 22 countries worldwide (108). Cases were patients with acute first stroke (within 5 days of symptoms onset and 72 hours of hospital admission). Controls had no history of stroke, and were matched with cases for age and sex. In 3,000 cases (n = 2,337, 78%, with ischaemic stroke; n = 663, 22% with intracerebral haemorrhagic stroke) and 3,000 controls, significant risk factors for all stroke were: history of hypertension, current smoking, waist-to-hip ratio, diet risk score, regular physical activity, diabetes mellitus, alcohol intake, psychosocial stress and depression, cardiac causes, and the apo-ratio in falling order. Together, these risk factors accounted for 88.1% of the population attributable risk for all stroke. Increased concentration of non-HDL-C was not associated with risk of ischaemic stroke, but was associated with reduced risk of intracerebral haemorrhagic stroke, whereas increased concentration of apoB was associated with increased risk of ischaemic stroke, but was not associated with risk of intracerebral haemorrhagic stroke. The apo-ratio was a stronger predictor of ischaemic stroke than was ratio of non-HDL-C/HDL-C.

#### **8.3. Other studies on stroke and atherosclerosis in the carotid arteries**

Kostapanos et al. (109) studied 163 patients aged 70 years (88 men) with a first-ever acute ischemic/non-embolic stroke and 166 volunteers (87 men) with no history of CV disease. Compared with subjects with an apo-ratio in the lowest quartile, those within the highest quartile had a 6.3-fold increase in the odds of suffering an ischemic stroke (p<0.001). This association remained significant after controlling for sex, age, smoking status, body mass index, waist circumference, glucose and insulin levels, the presence of hypertension and diabetes mellitus, and lipid profile parameters (adjusted OR = 3.02; 95% CI 5.16-7.83; p = 0.02). The findings support elevated apo-ratio as an independent predictor of ischemic stroke in individuals over age 70.

Park et al. (110) studied 464 statin or fibrate naïve Korean patients with acute ischemic stroke: intracranial (ICAS, n = 236), extracranial (n = 44), and no cerebral atherosclerotic stenosis (n = 184). The ICAS group showed a significantly higher apo-ratio than the other two groups. The apo-ratio of 0.93 was substantially increased in patients with advanced ICAS (3 or more intracranial stenoses), the highest quartile of the apo-ratio was an independent predictor of ICAS (OR, 2.13; 95% CI, 1.05 - 4.33). A dose–response relationship (multivariate analysis) was observed between the presence of advanced ICAS and the apo-ratio quartiles (ORs, 4.03, 4.88,

and 7.79, for the fourth quartile versus the first quartile). Patients having more metabolic syndrome components indicating MetS were more likely to have ICAS, advanced ICAS, and a higher apo-ratio (p < 0.001 for all). Thus, a higher apo-ratio is a predictor of ICAS rather than of extracranial atherosclerotic stenosis or no cerebral atherosclerotic stenosis. The apo-ratio might be a biomarker for ICAS in Asian patients with stroke.

### **8.4. The ISIS-study relating the apo-ratio to risk of MI**

This ISIS case–control study was conducted among 3,510 acute MI patients (without prior vascular disease, diabetes, or statin use) in UK hospitals and 9,805 controls (60). Relative risks (age, sex, smoking, and obesity-adjusted) were more strongly related to apoB than to LDL-C and, given apoB, more strongly negatively related to apoA-I than to HDL-C. The apo-ratio was substantially more informative about risk than LDL-C/HDL-C, TC/HDL-C, non-HDL-C, and TC. Relative risks within several subgroups of patients showed no clear heterogeneity of effect with respect to sex, smoking, or BMI. The strongest effects were seen in those aged 30-49 years but even at ages 70-79, a 2SD higher apo-ratio was associated with a highly significant (P < 0.00001) relative risk. Furthermore, the apo-ratio, if untreated, is stable over time. Given the usual value of apoB, the usual value of LDL-C (indicating sdLDL particles) the risk was significantly higher. They concluded that single measurements of apoB and apoA-I are more predictive than single measurements of LDL-C and HDL-C and that the apo-ratio is the single best predictor of all lipid fractions is consistent with previously reviewed results including the AMORIS study (3,44).
