Study design and subjects
The current study was cross-sectional observation study. Four hundred and eighty-five previously diagnosed T2D patients aged between 30 and 70 years attending the University Kebangsaan Malaysia Medical Center, Kuala Lumpur, Malaysia were randomly recruited into the study after obtaining their informed consent. Ethical approval was obtained from the National University of Malaysia Research and Ethics committee.
Sample and data collection
Waist circumference was measured midway between the lower rib margin and the superior iliac spine at the end of gentle expiration in a standing position. Blood pressure (BP) measurements were taken from each patient’s right arm in the seated position by using an Omron IntelliSense Automatic Blood Pressure Monitor after 10 min rest in a quiet room. Two to three successive BP readings were obtained at 5 minutes intervals and averaged. Fasting blood (5ml) was collected from each subjected and divided into two tubes, EDTA tube for HbA1c measurement and plain tubes for biochemical investigations. The plain tubes were centrifuged for 10 minutes at 3000 × g within 30 minutes of blood collection and the serum from each sample was separated into two Eppendorf tubes and immediately kept at −20°C until analysis. The treatment for each participant was collected from the patient data record at the University Kebangsaan Malaysia Medical Center,
Biochemical analyses and Glycated hemoglobin (HbA1c) measurements
Kits for the measurement of glucose, triglyceride and HDL cholesterol (reference number 10260, 10724, 10028 and 10018 respectively) were purchased from Human Company (Human GmbH, Wiesbaden, Germany). Human company elevated control sera (Humatrol P Reference number 13512) was used as quality control for these parameters. C-peptide was measured in an automated quantitative immunoassay analyzer (Immulite, DPC, Los Angeles, USA) using IMMULITE C-peptide kit (catalogue number LKPE1). Glycated hemoglobin (HbA1c) levels were determined by high performance liquid chromatography (VARIANT Hemoglobin A1c Reorder Pack, catalog no. 270-0003, Bio-Rad Laboratories, Inc., Richmond, California, USA) with lyphochek diabetes Bi-level controls (Catalogue number 740) as quality control. Insulin resistance was calculated using the Homeostasis Model Assessment (HOMA2) Calculator v2.2 available from Oxford Center for Diabetes, Endocrinology and Metabolism. This program used fasting C-peptide or insulin and blood glucose levels to calculate insulin resistance.
Assessment of metabolic syndrome
Metabolic syndrome was diagnosed based on the IDF and NCEP-R criteria. All subjects included in this study were previously diagnosed with T2D and therefore blood glucose was excluded from the five MetS criteria. The MetS in T2D was diagnosed according to NCEP-R that included two or more of the following abnormalities:
- Central obesity: waist circumference ≥102 cm for men or ≥ 88 cm for women
- Raised blood pressure: systolic blood pressure ≥ 130 mmHg or diastolic blood pressure ≥ 85mmHg or treatment of previously diagnosed hypertension
- Raised triglyceride level: ≥ 7 mmol/l or specific treatment for this lipid abnormality
- Reduced HDL cholesterol: men <1.03 mmol/l, women <1.29 mmol/l or HDL cholesterol treatment.
While according to the IDF criteria, MetS was defined by the presence of central obesity (waist circumference in Asian male ≥ 90 cm and female ≥ 80 cm) together with one of the other MetS criteria which includes; blood pressure, triglyceride, and HDL cholesterol with the same cut off point as NCEP-R.
Statistical analysis
The analyses were assessed by SPSS version 11.5 software (SPSS, Inc, Chicago, USA). The fasting blood glucose, glycated hemoglobin, C-peptide, and insulin resistance were log transformed as they were not normally distributed. Mean and 95% confidence intervals were transformed back and reported. The Cohen's Kappa (κ) test was used to evaluate the concordance between the IDF and NCEP-R criteria. The general linear model adjusted for age, sex, race and history of diabetes (as covariates) was used to study the correlation of MetS with glycemic control; fasting blood glucose, glycated hemoglobin, C-peptide and insulin resistance (as a set of dependent variables).