Lipid profile-GTT

• Serum Cholesterol Level
• i. In 1970s, data from the Framingham epidemiological study demonstrated that increase in serum cholesterol level is associated with and increased risk of death from CHD. For every 10% lowering of cholesterol, CHD mortality was reduced by 13%. Reduction of cholesterol may not only decrease the lipid content of the plaque, but can also reduce the accumulation of monocytes and macrophages.
• ii. In healthy persons, cholesterol level varies from 150 to 200 mg/dL. If other risk factors are present, cholesterol level should be kept preferably below 180 mg/dL. Values around 220 mg/dL will have moderate risk and values above 240 mg/dL will need active treatment.
• iii. Females have a lower level of cholesterol which affords protection against atherosclerosis.
• iv. Plasma cholesterol levels would tend to slowly rise after the 4th decade of life in men and postmenopausal women.

LDL-Cholesterol Level

• In 1988, the National Cholesterol Education Program (NCEP) identified elevated LDL-C as a primary risk factor for CHD.
• Blood levels under 130 mg/dL are desirable. Levels between 130 and 159 are borderline; while above 160 mg/dL carry definite risk. Hence LDL is “bad” cholesterol.
• Oxidized LDL initiates fatty streaks, which is the starting point of atheroma formation. Plaque instability and rupture are also associated with oxidised LDL.
• Plasma concentrations of small dense LDL (sd-LDL) are associated with the prevalence of cardiovascular events. Recently, simple homogeneous assay for sd-LDL-cholesterol has been developed.

HDL-Cholesterol Level

• The HDL level above 60 mg/dL protects against heart disease. Hence, HDL is “good” cholesterol. A level below 40 mg/dL increases the risk of CAD.
• For every 1 mg/dL drop in HDL, the risk of heart disease rises 3%.
• If the ratio of total cholesterol/HDL is more than 3.5, it is dangerous. Similarly, LDL:HDL ratio more than 2.5 is also detrimental.
• In some cases, even though patient may have high HDL, but may have dysfunctional HDL.
• Thus low lecithin-cholesterol acyl transferase activity is a strong positive risk marker for ischemic heart disease, independent of HDL-cholesterol. Hence, importance is for HDL activity and not for HDL concentration.

• Apoprotein Levels and Ratios Apo A-I is a measure of HDL-cholesterol (good) and apo B measures LDL-cholesterol (bad). Ratio of Apo B : A-I is the most reliable index. The ratio of 0.4 is very good; the ratio 1.4 has the highest risk of cardiovascular accidents.
• Lp(a) Lp(a) inhibits fibrinolysis. Levels more than 30 mg/dL increase the risk 3 times; and when increased Lp(a) is associated with increased LDL, the risk is increased 6 times. Nicotinic acid will reduce serum Lp(a) level
• Serum Triglyceride Normal level is 50–150 mg/dL. Blood level more than 150 mg/dL is injurious to health.

High Sensitivity C Reactive Protein (hsCRP)

• It is also called ultra sensitive CRP. It measures low levels of CRP using nephelometry or immunoturbidimetry technique. Since the method has high sensitivity, even small quantity (1–10 ng/dL) could be measured.
• It is a marker for risk for atherosclerosis and is used as a predictor for future myocardial infarction within the next 12 months.
• Because half of heart attacks and strokes happen in patients who do not have high levels of cholesterol in their blood, measurement of hs-CRP may help to identify patients who are at risk and may need medical treatment. The hs-CRP test clearly adds to the predictive value.
• Less than 1 mg/L (0.1 mg/dL) is considered as low risk and single measurement is sufficient.
• Levels between 1–3 mg/L are border line, indicating some risk, and will need assessment of serial samples at 1 week intervals.
• Levels more than 3 mg /L is having high risk for future MI, and will need active medical intervention.

Glucose tolerance test

• The ability of a person to metabolize a given load of glucose is referred to as glucose tolerance.
• Types
• OGTT (oral glucose tolerance test) commonly used
• GTT (intravenous glucose tolerance test) rarely used
• Conducting the Glucose Tolerance Test
• 1. At about 8 am. a sample of blood is collected in the fasting state. Urine sample is also obtained. This is denoted as the "0" hour sample.
• 2. Glucose load dose: The dose is 75 g anhydrous glucose (82.5 g of glucose monohydrate) in 250-300 m L of water. This dose is fixed for an adult, irrespective of body weight. (When the test is done in children, the glucose dose is adjusted as 1.75 g/kg body weight). In order to prevent vomiting, patient is asked to drink it slowly (within about 5 minutes). Flavoring of the solution will also reduce the tendency to vomit.
• 3. Sample collection: As per current WHO recommendations. 2 samples are collected, one at fasting ("0" hr sample) and 2-hour post-glucose load. Urine samples may also be collected along with these blood samples.
• Impaired Glucose Tolerance (IGT) It is otherwise called as Impaired Glucose Regulation (IGR). Here blood sugar values are above the normal level, but below the diabetic levels. This is sufficient to get a correct assessment of the patient. Normal Values and Interpretations
• In IGT. the fasting plasma glucose level is between 110 and 126 mg/dL and 2-hour post-glucose value is between 140 and 200 mg/dL Such persons need carcful follow-up bccausc IGT progresses to frank diabetes at the rate of 2% patients per year.