P5332Magic mirror on the wall, can we reach our LDL-C goal? Comparison of calculated LDL-C and direct measured LDL-C levels in atherogenic dyslipidemia condition

Background

LDL-C represents the primary lipoprotein target for reducing cardiovascular risk. LDL-C can either be calculated or measured directly. Friedewald equation has certain limitations especially with high triglyceride and low LDL-C levels. Although a number of automated direct LDL-C assays are commercially available, non of them is considered to be equivalent to the “gold standard” of direct LDL-C, beta quantitation, a complex and expensive process that is unavailable in routine clinical practice. In atherogenic dyslipidemia condition (ADC) (triglycerides≥2.3 mmol/L and HDL-C<1.0 mmol/L) non-HDL-C and remnant cholesterol are proven additional risk factors.

Purpose

We compared one of the direct homogeneous assays with the widely used Friedewald's and the new Martin/Hopkins methods of estimation of LDL-C to see the differences in average LDL-C, remnant cholesterol and non-HDL-C levels and in availability of less than 1.8 mmol/L of LDL-C in atherogenic dyslipidemia condition.

Methods

We investigated 14 906 lipid profiles from fasting blood samples of Hungarian individuals with triglycerides <4.5 mmol/L. Total cholesterol (TC), HDL-C, triglycerides (TG) and direct LDL-C (D-LDL-C) were measured directly by the enzimatic assays. We also estimated calculated LDL-C by the Friedewald's formula (F-LDL-C) and by using the new Martin/Hopkins estimation (MH-LDL-C). We have now prepared first a variant of Martin/Hopkins table in mmol/L, in which the modified adjustable factors of 2.2 are included. We determined also non-HDL-C and remnant cholesterol (RC) as a difference of non-HDL-C and F-LDL-C (F-RC), MH-LDL-C (MH-RC), D-LDL-C (D-RC).

Results

In the investigated population 19.25% was F-LDL-C, 15.48% MH-LDL-C and 7.92% D-LDL-C below 1.8 mmol/L. ADC occurred at 8.12%. For ADC, when F-LDL-C<1.8 mmol/L (A), mean values for F-LDL-C, MH-LDL-C, D-LDL-C and non-HDL-C were 1.23±0.4; 1.65±0.39; 2.06±0.4 and 2.46±0.5 mmol/L respectively. These mean levels were 1.01±0.36; 1.4±0.3; 1.83±0.3 and 2.15±0.34 mmol/L for MH-LDL-C<1.8 mmol/L (B). For D-LDL-C<1.8 mmol/L (C), mean values were 0.79±0.35; 1.13±0.26; 1.54±0.19 and 1.83±0.25 mmol/L respectively. The average RC values (in mmol/L) for A were F-RC: 1.23±0.36; MH-RC: 0.81±0.18; D-RC: 0.4±0.17, for B 1.14±0.33; 0.74±0.14; 0.32±0.13, and for C 1.04±0.27; 0.70±0.1; 0.29±0.12 respectively.

Conclusions

The Friedewald equation tends to underestimate and the homogeneous enzimatic direct LDL-C assays to overestimate the LDL-C levels compared to the new, accurate, calculated LDL-C values in atherogenic dyslipidemia condition. Based on the data presented in our investigation we should like to propose that more realistic vasculo-protective lipid status can be attained if we calculate LDL-C using the Martin/Hopkins estimation.

Frequency of the R3500Q mutation of the apolipoprotein B-100 gene in a sample screened clinically for familial hypercholesterolemia in Hungary

Familial hypercholesterolemia (FH) and familial defective apolipoprotein B-100 (FDB) cause early onset of coronary heart diseases (CHD). According to the recommendations of the international MEDPED program, we tried to find FH cases. We analyzed 73 FH probands and their 304 first-degree relatives. A total of 39 probands were found from the 21000 subjects screened (1:538) from family doctors' registers recording all citizens, while the remaining 34 were derived from screened patients from lipid clinics. In our FH probands, four cases of FDB (R3500Q mutation) were diagnosed with allele-specific PCR, and the mutation was also detectable in five cases out of seven living family members. In the remaining 69 FH families, 156 people were diagnosed clinically with FH, and 31.8% of the males (against 13% of the not clinically diagnosed FH males, P<0.01), and 32.4% of the females (against 13.5% of the not clinically diagnosed FH females, P<0.01) suffered from early onset CHD. The plasma total cholesterol level of the FDB patients, especially in the younger patients, was very close to normal values. Therefore, the FDB patients seem to be under-represented in this type of survey. Because FDB is one of the independent causes of early onset CHD, the R3500Q mutation should be considered in families with a high frequency of cardiovascular diseases.

Attaining United States and European guideline LDL-cholesterol levels with simvastatin in patients with coronary heart disease (the GOALLS study)

The effectiveness and safety of simvastatin in reducing low-density lipoprotein cholesterol (LDL-C) to target levels in patients with coronary heart disease (CHD) were evaluated in the GOALLS (Getting to Appropriate LDL-C Levels with Simvastatin) study. This multinational, multicentre, prospective, open-label, study consisted of a six-week diet washout period followed by a 14-week titrate-to-goal treatment period with simvastatin. One hundred and ninety-eight men and women with documented CHD and a fasting LDL-C level between 115 mg/dl (3.0 mmol/l) and 180 mg/dl (4.7 mmol/l) and triglycerides (TGs) < or = 400 mg/dl (4.5 mmol/l) were enrolled. The patients were started on 20 mg simvastatin with dose titration up to 80 mg if the LDL-C remained above 100 mg/dl at weeks 6 and 10. The key efficacy parameters were the percentage of patients achieving US and European LDL-C goals [< or = 100 mg/dl (2.6 mmol/l) and < or = 115 mg/dl (3.0 mmol/l), respectively]. Safety was evaluated by monitoring laboratory tests and recording adverse events. After 14 weeks of simvastatin (20-80 mg) treatment, approximately 90% of the patients achieved LDL-C goals according to US (87%) and European (94%) guidelines. Most patients (72-93%) achieved target LDL-C levels on 20 mg simvastatin. An estimated 14% of the patients required titration to the 80 mg dose. Treatment with simvastatin (20-80 mg) produced statistically significant improvements in all measured lipid variables by the end of the study. The mean reductions in total cholesterol and LDL-C, and the median reduction in TG, were 28%, 41% and 16%, respectively. The increase in high-density lipoprotein cholesterol and apolipoprotein A-1 were 5% and 4%, respectively. Simvastatin was well tolerated across the dosage range. In conclusion, simvastatin, 20-80 mg/day, was safe and highly effective at reducing LDL-C levels. The recommended US and European LDL-C treatment goals were achieved in approximately 90% of the patients. These goals were similarly achieved for a variety of high-risk sub-groups (hypertensives, diabetics and elderly patients).

[Incidence of familial defective apolipoprotein B-100 in cases of patients diagnosed with familial hypercholesterolemia]

Familial Hypercholesterolemia (FH) and Familial Defective Apolipoprotein B-100 (FDB) are monogenic, autosome, dominantly inherited diseases appearing as type II/a primary hypercholesterolemia. The frequency of the heterozygositic forms is 1:700-1:500 in European population. Both forms of hypercholesterolemia causes early onset coronary heart diseases (CHD). According to the recommendations of the international MED-PED program (Make Early Diagnoses--Prevent Early Death), we found 73 FH cases and their 377 first relatives (parents, siblings, children) were also assessed. 156 patients were diagnosed clinically FH (131 alive and 25 deceased), and 31.8% of the males and 32.4% of females suffered from early onset CHD. One family with FH consists of 5.46 members on the average and there are 2.39 FH patients in one family. In our FH cohort four patients with FDB (R3500Q mutation) were diagnosed with allelspecific PCR, and the mutation was detectable also in 9 cases out of 11 living family members. The plasma total cholesterol level of the FDB patients--especially at younger age--was very close to the normal values, which is in contrast to the findings in FH patients. Nevertheless, FDB can be one of the independent causes of the early onset CHD. Therefore, in families with high frequency of cardiovascular diseases the R3500Q mutation has to be considered.

[Reducing low density lipoprotein-cholesterol levels by apheresis]

The predominate number of homozygote familial hypercholesterolemic and approximately 20% of heterozygotes are resistant to low cholesterol diet and lipid lowering pharmacological treatment even in combination of 2 or more drugs. In such cases, the selective lipoprotein apheresis has become a promising alternative and indicated absolute (homozygotes) or relative (heterozygotes). The combination of low density lipoprotein apheresis, together with diet and drugs, should allow a maximal lowering of low density lipoprotein-cholesterol (-60-70%). Besides low density lipoprotein, various apheresis procedures may also eliminate other potentially atherogenic factors, such as lipoprotein(a) and fibrinogen and acutely improve the haemo-rheological status of the patient. The authors review several lipoprotein apheresis procedures with varying degrees of selectivity, those have and furthermore analysis the advantages and disadvantages and cost of each procedure.