Diagnosis
The diagnosis of hyperlipidemia is made by taking a blood sample. Patients should be fasting for 12 hours before taking the blood sample in order not to falsify the blood lipid values by ingested food. A screening is carried out by the family doctor from the age of 35.
The screening includes the determination of total cholesterol and HDL cholesterol. Regular screening is also performed in patients with risk factors for atherosclerosis, for example diabetics. The determination of a complete lipid status goes beyond the normal screening: In addition to HDL cholesterol and total cholesterol, the neutral fats in the blood are also determined.
The amount of LDL cholesterol can then be calculated from these values. The quotient total cholesterol/HDL cholesterol is then calculated: Values below 4 indicate a low risk of atherosclerosis, values between 4 and 4.5 are within the normal range. Values above 4.5 indicate an increased risk of atherosclerosis.Hypertriglyceridemia (increase in neutral fats in the blood) is said to occur at levels above 150mg/dl (1.7mmol/l).
Hypercholesterolemia (increased cholesterol levels) is defined by cholesterol levels above 200mg/dl (5.2mmol/l). If one wants to find out more about the patient’s hyperlipidemia, an electrophoresis (examination of the blood in an electric field) can be performed. In this procedure, the different fats in the blood are divided.
If hyperlipidemia is suspected to be hereditary, genetic tests can be performed. Hyperlipidemias are classified either clinically or by electrophoresis according to Frederickson. The clinical classification is based on the respective elevated fat type.
A distinction is made between hypercholesterolemia, hypertriglyceridemia, combined hyperlipidemia and lipoprotein disorders. The classification according to Frederickson is based on the lipoproteins involved (protein particles that transport fats in the blood), which can be identified by electrophoresis. The lipoproteins differ in composition and function from neutral fats and cholesterol.
According to Frederickson, 5 types are distinguished (type I, type IIA, type IIB, type III and type IV):
- Type I: In type I according to Frederickson, there is a significant increase in neutral fats in the blood, in addition the chylomicrons are increased. Chylomicrons transport the fat absorbed with food from the intestine via the lymph into the bloodstream. Here the neutral fats are split and then absorbed into fat and muscle cells.
Type I according to Frederickson is very rare.
- Type IIA: In type IIA the total cholesterol levels are elevated. The LDL lipoproteins are particularly involved here. LDL lipoproteins transport cholesterol from the liver to the other parts of the body, where it is absorbed into the cells by LDL receptors.
The cholesterol is built into cell walls and serves as the basis for bile acid or steroid hormones. Elevated LDL lipoproteins represent a significant risk factor for atherosclerosis. About 10% of all patients with hyperlipidemia have type IIA according to Frederickson.
- Type IIB: In type IIB, both total cholesterol and neutral fats are elevated.
Involved lipoproteins are the LDL-lipoprotein (transports mainly cholesterol) and the VLDL-lipoprotein. The VLDL-lipoprotein transports mainly neutral fats produced in the liver from the liver to the fat and muscle cells of the body. Increases in VLDL (as well as increases in LDL) are a risk factor for atherosclerosis.
Type IIB according to Frederickson comprises about 15% of all hyperlipidemias.
- Type III: Type III describes an increase in total cholesterol and neutral fats. The lipoproteins involved are so-called VLDL remnants or IDL lipoproteins. They are degradation products of the VLDL lipoproteins and, if increased, are also a risk factor for atherosclerosis.
About 5% of patients with hyperlipidemia have type III according to Frederickson.
- Type IV: This type is the most common with 70%. In type IV, neutral fats are elevated, and VLDL lipoproteins (which mainly transport neutral fats) are involved, which are a risk factor for atherosclerosis.
The ICD-10, the currently valid diagnostic classification system of the WHO, classifies the different forms of hyperlipidemia according to the respective elevated components. Different codes summarize different clinical pictures in one diagnosis: E78.
0 describes a pure cholesterol increase, E78. 1 a pure hypertriglyceridemia (increase in neutral fats). E78.
2 describes mixed forms, E78. 3 an increase in chylomicrons. Chylomicrons consist mainly of neutral fats and transport the fats taken in with food from the intestine via the lymph into the bloodstream.
E78. 4 and E78. 5 describe other or unspecified hyperlipidemia.
E78. 6 describes deficiencies of various lipoproteins, E78. 8 and E78. 9 describe a different or an unspecified disorder of lipoprotein metabolism.
