Measurement performance of reagent manufacturers by Centers for Disease Control and Prevention/Cholesterol Reference Method Laboratory Network lipid standardization specified for metabolic syndrome-focused health checkups program in Japan

Heart Rate Variability, Insulin Resistance, and Insulin Sensitivity in Japanese Adults: The Toon Health Study

BACKGROUND

Although impaired cardiac autonomic function is associated with an increased risk of type 2 diabetes in Caucasians, evidence in Asian populations with a lower body mass index is limited.

METHODS

Between 2009-2012, the Toon Health Study recruited 1899 individuals aged 30-79 years who were not taking medication for diabetes. A 75-g oral glucose tolerance test was used to diagnose type 2 diabetes, and fasting and 2-h-postload glucose and insulin concentrations were measured. We assessed the homeostasis model assessment index for insulin resistance (HOMA-IR) and Gutt's insulin sensitivity index (ISI). Pulse was recorded for 5 min, and time-domain heart rate variability (HRV) indices were calculated: the standard deviation of normal-to-normal intervals (SDNN) and the root mean square of successive difference (RMSSD). Power spectral analysis provided frequency domain measures of HRV: high frequency (HF) power, low frequency (LF) power, and the LF:HF ratio.

RESULTS

Multivariate-adjusted logistic regression models showed decreased SDNN, RMSSD, and HF, and increased LF:HF ratio were associated significantly with increased HOMA-IR and decreased ISI. When stratified by overweight status, the association of RMSSD, HF, and LF:HF ratio with decreased ISI was also apparent in non-overweight individuals. The interaction between LF:HF ratio and decreased ISI in overweight individuals was significant, with the odds ratio for decreased ISI in the highest quartile of LF:HF ratio in non-overweight individuals being 2.09 (95% confidence interval, 1.41-3.10).

CONCLUSIONS

Reduced HRV was associated with insulin resistance and lower insulin sensitivity. Decreased ISI was linked with parasympathetic dysfunction, primarily in non-overweight individuals.

HDL cholesterol performance using an ultracentrifugation reference measurement procedure and the designated comparison method

BACKGROUND

Accurate high-density lipoprotein cholesterol (HDL-C) measurements are important for management of cardiovascular diseases. The US Centers for Disease Control and Prevention (CDC) and Cholesterol Reference Method Laboratory Network (CRMLN) perform ultracentrifugation (UC) reference measurement procedure (RMP) to value assign HDL-C. Japanese CRMLN laboratory (Osaka) concurrently runs UC procedure and the designated comparison method (DCM). Osaka performance of UC and DCM was examined and compared with CDC RMP.

METHODS

CDC RMP involved UC, heparin-MnCl₂ precipitation, and cholesterol analysis. CRMLN DCM for samples containing <200 mg/dl triglycerides involved 50-kDa dextran sulfate-MgCl2 precipitation and cholesterol determination.

RESULTS

HDL-C regression equations obtained with CDC (x) and Osaka (y) were y=0.992x+0.542 (R(2)=0.996) for Osaka UC and y=1.004x-0.181 (R(2)=0.998) for DCM. Pass rates within ±1 mg/dl of the CDC target value were 91.9 and 92.1% for Osaka UC and DCM, respectively. Biases at 40 mg/dl HDL-C were +0.22 and -0.02 mg/dl for Osaka UC and DCM, respectively.

CONCLUSIONS

Osaka UC and DCM were highly accurate, precise, and stable for many years, assisting manufacturers to calibrate products for clinical laboratories to accurately measure HDL-C for patients, calculate non-HDL-C, and estimate low-density lipoprotein cholesterol with the Friedewald equation.

Present status of the standardization of HDL-C, LDL-C, and TG measurement values available in Japan

BACKGROUND

Control sera used as evaluation samples in external quality control of HDL-C and LDL-C sometimes show disparities in results between direct methods differing in reaction principles. As a result, the present standardization status is unclear. In 2008, we investigated the present status of standardization of HDL-C, LDL-C, and TG measurement values available in Japan.

SUBJECTS AND METHODS

To evaluate accuracy, refrigerated fresh human serum pools used as samples were analyzed irrespective of the manufacturer's method. To evaluate precision, a questionnaire survey regarding the internal quality control status at each institution was carried out. As evaluation criteria, the permissible limits of error of BA and CVA based on JSCC proposals, and the accuracy and imprecision criterion NCEP proposals were used.

RESULTS

There were 70 participating institutions for HDL-C, 65 for LDL-C, and 71 for TG. TG values from the institutions showed 83.1-91.5% for both the JSCC BA range and the NCEP criterion range. HDL-C values within the JSCC BA range were 81.4-82.6% and within the NCEP criterion range the value was 98.6%. Similarly, LDL-C values within the JSCC BA range were 89.2% and within the NCEP criterion range the value were 81.5-83.1%, respectively. Concerning precision, a questionnaire regarding internal quality control of each institution was completed. More than 90% of the institutions showed values within the CVA range proposed by the JSCC for all of HDL-C, LDL-C, and TG.

CONCLUSION

Standardization of lipid assays used for metabolic syndrome-based health checkups has been mostly achieved.

[Cholesterol controversy: cutoff point of low-density lipoprotein cholesterol level in Guidelines by Japan Atherosclerosis Society]

In 2007, the Japan Atherosclerosis Society published the Guidelines for prevention of atherosclerotic cardiovascular diseases. However, the guidelines have several flaws with regard to the cutoff level of serum low-density lipoprotein cholesterol (LDL-C). First, LDL-C level is used instead of serum total cholesterol (TC) level in the guidelines. In this case, they must show at least some basic data on the relationship between LDL-C level and mortality or morbidity from coronary heart disease (CHD). Second, it was recommended that the LDL-C level be below 140 mg/dL or 3.6 mmol/L (corresponding to a TC level of 220 mg/dL or 5.7 mmol/L, respectively). These levels are unreasonable considering that the TC levels of 240-260 mg/dL are optimal in terms of all-cause mortality for the Japanese population. Third, although there are big differences in mortality and morbidity from CHD between sexes, they discussed the matter without considering these differences. Last but not least, the conflict of interest of the editors of the guidelines has never been disclosed. The Japanese population has a lower CHD mortality and incidence than populations from other industrialized countries despite an increase in serum TC level in the former. In populations with a markedly lower coronary mortality or morbidity such as the Japanese population, it is still important to determine the optimal cutoff level of LDL-C to prevent the development of CHD and other atherosclerotic diseases.

Ten-year evaluation of homogeneous low-density lipoprotein cholesterol methods developed by Japanese manufacturers. Application of the Centers for Disease Control and Prevention/Cholesterol Reference Method Laboratory Network lipid standardization protocol

AIM

The risk index for atherosclerotic cardiovascular diseases in the Japanese metabolic syndrome-focused health checkup program was changed from total cholesterol (TC) to low-density lipoprotein cholesterol (LDL-C). We discuss the validity of this change with respect to standardization.

METHODS

The beta-quantification procedure of the Centers for Disease Control and Prevention (CDC) uses the LDL-C reference value as a target. Clinical laboratories and commercial manufacturers use homogeneous LDL-C methods for standardization. (A) For clinical laboratories, LDL-C in 648 samples requested from 108 hospitals was analyzed. (B) Manufacturers participated in the CDC/Cholesterol Reference Method Laboratory Network LDL-C standardization protocol. The standardization was conducted with a performance follow-up for the 10-year period from 1998 to 2008 at 2-year intervals, 6 times.

RESULTS

(A) In clinical laboratories, acceptable LDL-C levels within ±4% of the CDC's criteria remained 70.4%, 456 of 648 subjects. Negative maximum bias deviating from the LDL-C target value was -35.8%, -52.5 mg/dL, and positive maximum bias was +24.5%, +32.3 mg/dL. (B) For manufacturers, the standardization achievement rate of the analytical reagent/instrument/calibrator system in the last four standardizations from 2002 to 2008 remained on average 66.6%, far lower than the level required.

CONCLUSIONS

The standardization achievement rate of homogeneous LDL-C methods was much low-er than that of TC. TC should still be used as a risk index for atherosclerotic cardiovascular diseases. The standardization achievement rate of homogeneous LDL-C should be maintained at 100%, at least using samples with normal lipoprotein profiles. The accuracy and specificity of LDL-C should be further improved before practical and clinical use.

More intensive lipid lowering is associated with regression of coronary atherosclerosis in diabetic patients with acute coronary syndrome--sub-analysis of JAPAN-ACS study

AIM

We have shown that aggressive lipid lowering by pitavastatin and atorvastatin results in marked regression of atherosclerotic coronary lesions after acute coronary syndrome (ACS). The purpose of this study was to address the association of lipid levels after statin therapy with regression of atherosclerotic coronary lesions and major cardiovascular events in patients after ACS.

METHODS

JAPAN-ACS is a prospective, randomized open-label study performed at 33 centers in Japan. Patients with ACS undergoing intravascular ultrasound (IVUS)-guided percutaneous coronary intervention (PCI) were randomly assigned to receive either 4 mg/day pitavastatin or 20 mg/day atorvastatin within 72 hours after PCI. IVUS image was obtained in 251 patients, including 73 diabetic patients. Lipid profiles at the end of the study were divided into quartiles and the association with the percent change in non-culprit coronary plaque volume (PV) was assessed in total and diabetic patients. We also studied whether baseline and follow-up levels of HDL-cholesterol are associated with restenosis after PCI.

RESULTS

Decreasing LDL-cholesterol, non-HDL-cholesterol, LDL-C/HDL-C ratio, apolipoprotein B quartiles were associated with a progressively smaller plaque burden in total and diabetic patients. In diabetic patients, further reduction of these parameters was associated with a significantly greater reduction in PV. We also found that patients with lower HDL-cholesterol had a significantly higher incidence of target lesion revascularization.

CONCLUSIONS

Early intensive statin therapy in patients after ACS results in remarkable regression of coronary PV. Diabetic patients can have a benefit with more intensive therapy to achieve a lower target level in Japanese.

Dyslipidemia and cardiovascular disease: a series of epidemiologic studies in Japanese populations

Although the causal relationships of high serum levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) with coronary artery disease (CAD) are well established, there have been few community-based epidemiologic studies of these relations in Japan. Furthermore, even when analysis is restricted to ischemic stroke, the relationship between dyslipidemia and stroke is very weak. Accordingly, it is difficult to perform cohort studies of dyslipidemia and cardiovascular disease. A series of studies, such as the NIPPON DATA (National Integrated Project for Prospective Observation of Non-communicable Disease and Its Trends in the Aged) cohort study of a representative sample of Japanese, have greatly increased existing evidence. NIPPON DATA80 revealed a clear positive relationship between TC and CAD, and indicated that reverse causality between hypocholesterolemia and liver disease may increase all-cause mortality in hypocholesterolemic Japanese. NIPPON DATA90 showed that serum high-density lipoprotein cholesterol (HDL-C) was inversely associated with all-cause mortality, even when HDL-C was very high. NIPPON DATA80 revealed that low-normal levels of serum albumin and TC are associated with a decline in activity during old age, especially in women. The Suita study-a unique cohort study of urban residents-showed that LDL-C and non-HDL-C were equally accurate in predicting the incidence of myocardial infarction. Further research of this quality is needed to ascertain the public health burden of dyslipidemia in Japan.