Cholesterol is an essential (vital) sterol (membrane lipid) and an important component of the plasma membrane. In the body, it serves as a precursor for steroid hormones and bile acids, among other things. It enters the bloodstream in two ways. On the one hand, the liver synthesizes cholesterol, and on the other, it is ingested in the daily diet. Since lipids (blood fats) such as cholesterol are not soluble in the blood and cannot normally be transported in the blood, they must be bound to lipoproteins. The serum cholesterol level is composed of the HDL cholesterol (HDL-C; engl. : high density lipoprotein) and the LDL cholesterol (LDL-C; engl. : low density lipoprotein). The higher the lipid content in cholesterol, the lower the density and the more harmful the compound. LDL cholesterol, for example, has a total lipid content of about 75% and HDL cholesterol of just over 50%. HDL cholesterol is able to take up cholesterol from the vessels – even from pre-existing deposits – and transport it back to the liver (reverse cholesterol transport, RCT) with the aim of excreting the cholesterol; this occurs either directly or after conversion to bile acids.LDL cholesterol has a completely different effect. It transports cholesterol from the liver to the individual tissues of the body. LDL cholesterol and other lipoproteins containing cholesterol are directly involved in the development and progression of atherosclerosis (hardening of the arteries). For recommended actions for adequate diagnosis, therapy, and long-term treatment of dyslipoproteinemia, see Deutsche Gesellschaft zur Bekämpfung von Fettstoffwechselstörungen und ihren Folgeerkrankungen DGFF (Lipid-Liga) e. V..
The procedure
Total cholesterol concentration can be determined from your blood sample using a laboratory diagnostic test. Material needed
- Blood serum
- Or LiH plasma
Preparation of the patient
- For blood collection, you must appear fasting – without having eaten anything 12-16 hours before. [no longer required]Notice. According to an epidemiological study, it is irrelevant for the prognostic information of the LDL cholesterol value whether the patients are fasting or not before the blood collection. This is also confirmed by experience from Denmark, where laboratories have been accepting blood samples from postprandial (“after eating”) patients for determination of the lipid profile since 2009.
- Special diets or affecting medications will be discontinued by your physician, if necessary, three days prior to blood collection.
- A control examination will be performed by your doctor in the event of pathological results after approximately two weeks.
Interfering factors
- Avoid long jams!
- Red rice can lower serum cholesterol levels via inhibition of HMG-CoA reductase.
The following values are determined:
- Total cholesterol
- LDL cholesterol (LDL-C)
- HDL cholesterol (HDL-C)
Normal values for total cholesterol
| Age | Normal values [mg/dl] | [mmol/l] |
| > 40th year of life | < 240 mg/dl | < 6.2 mmol/l |
| 30-40 years of age | <220 mg/dl | < 5.7 mmol/l |
| 20-29 years of age | <200 mg/dl | < 5.2 mmol/l |
| < 19 years of age | < 170 mg/dl | < 4.4 mmol/l |
| Children | < 170 (-200 mg/dl) | < 4.4 (-5.2 mmol/l) |
| Infants | < 190 mg/dl | < 4.9 mmol/l |
| Newborn | < 170 mg/dl | < 4.4 mmol/l |
Conversion factor
- Mg/dl x 0.02586 = mmol/l
Normal values for LDL cholesterol
| Age | Normal values [mg/dl] | [mmol/l] |
| Adult | < 160 mg/dl | < 4,16 |
| Children | < 100 mg/dl | < 2,6 |
| Infants | 45-117 mg/dl | 1,17-3,04 |
| Newborn | 59-217 mg/dl | 1,53-5,64 |
The higher the LDL level, the higher your risk of atherosclerosis!
| LDL cholesterol[mg/dl] | [mmol/l] | Classification of the risk of atherosclerosis |
| < 100 mg/dl | < 2,6 | optimal |
| 100-129 mg/dl | 2,6-3,35 | almost optimal |
| 130-159 | 3,38-4,13 | borderline elevated |
| 160-189 mg/dl | 4,16-4,91 | Increases |
| > 190 mg/dl | > 4,94 | strongly increased |
Normal values for HDL cholesterol
| Age | Normal values [mg/dl] | [mmol/l] |
| Men | 35-55 mg/dl | 0,91-1,43 |
| Women | 45-65 mg/dl | 1,17-1,69 |
| Children | 22-89 mg/dl | 0,57-2,31 |
| Infants | 13-53 mg/dl | 0,34-1,38 |
| Newborn | 22-89 mg/dl | 0,57-2,31 |
The lower the HDL level, the higher your risk of atherosclerosis! Conversion factor
- Mg/dl x 0.02586 = mmol/l
Note: HDL levels above 60 milligrams/deciliter (1.5 mmo/L) had a nearly 50 percent increased risk of death from cardiovascular disease or myocardial infarction in one study.
Normal values for the LDL/HDL quotient
The LDL/HDL quotient (LDL divided by HDL) is a very good indicator for estimating atherosclerosis risk.
| LDH/HDL quotient | Interpretation |
| < 3,0 | Target value (ideal) |
| 3,0 – 5,0 | Increased risk |
| ≥ 5 | high risk |
Standard values for non-HDL cholesterol.
Non-HDL cholesterol is the difference between the measured values of total cholesterol and HDL cholesterol. Thus, it also includes the atherogenic VLDL , IDL , and small-dense-LDL fractions. Risk category and non-HDL target values for triglyceride levels >200 mg/dl (>2.28 mmol/l).
| Non-HDL target values | Risk category |
| < 100 mg/dl (< 2.59 mmol/l) | At very high risk documented coronary artery disease (CAD) or diabetes mellitus or eGFR < 60 ml/min or HeartScore > 10% (www.heartscore.org) |
| < 130 mg/dl (< 3.37 mmol/l) | At high risk, prominent individual risk factors (eg, familial hypercholesterolemia, severe hypertension) or HeartScore >5% to <10%. |
| < 145 mg/dl (< 3.75 mmol/l) | Moderate-risk and low-risk HeartScore <5 |
Indications
- As a routine parameter to determine the risk of atherosclerosis.
- In children and adolescents whose parents or first-degree relatives have cardiovascular disease before the age of 60 years
- In children of parents, some of whom have familial hyperlipidemia or cholesterol > 300 mg/dl (> 7.8 mmol/l)
- In patients with a triglyceride level of > 200 mg/dl and metabolic dyslipoproteinemias (eg, type 2 diabetes mellitus, metabolic syndrome, android body fat distribution, that is, abdominal/visceral, truncal, central body fat (apple type), etc.).
- Therapy control during treatment with lipid-lowering drugs.
Interpretation
Interpretation of elevated values
1. hereditary primary or pure hypercholesterolemia, respectively:
- Polygenic hypercholesterolemia, type IIa, very common, high risk of atherosclerosis.
- Familial hypercholesterolemia, type IIa, frequency heterozygous 1: 500, homozygous 1: 1,000,000, very high risk (heterozygous) or extremely high risk (homozygous).
- Combined hyperlipidemia type IIa, IIb or IV, frequency 1: 300, high risk.
- Familial defective Apo B100 (FDB), type IIa, frequency 1: 100 – 1: 300, high risk.
Screening of children, adults, and families for suspected familial hypercholesterolemia (FH) is required if:
- Total cholesterol is higher than 310 mg/dl (8 mmol/l) in an adult and higher than 230 mg/dl (6 mmol/l) in a child
- FH has been diagnosed in a family member
- An early onset coronary artery disease (CAD) or xanthomas (lipid deposits) on the tendons exist
- sudden cardiac death (PHT) has occurred at a relatively early stage of life
2. secondary hypercholesterolemia:
- Obesity (overweight)
- Diet – too much saturated fat and cholesterol.
- Lack of exercise
- Smoking
- Pregnancy
- Hyperuricemia (gout)
- Hypothyroidism (hypothyroidism)
- Poorly adjusted diabetes mellitus
- Chronic diseases of the liver, kidneys or gallbladdersuch as hepatoma – benign or malignant neoplasm of liver cells,Nephrotic syndrome – clinical symptom complex associated with:
- Proteinuria (excretion of protein in the urine).
- Hypo- and dysproteinemia (deviations in the ratio of the protein bodies of the blood plasma).
- Hyperlipidemia (lipid metabolism disorder).
- Hypocalcemia (calcium deficiency)
- Accelerated ESR (erythrocyte sedimentation rate).
- Edema formation (water retention)
- Anorexia nervosa (anorexia)
- Acute intermittent porphyria – hereditary enzyme defect with impaired porphyrin synthesis in the liver.
- Some medications may contribute to LDL cholesterol elevation:
- Androgens
- Beta-receptor blockers (beta-blockers)
- Diuretics
- Glucocorticoids (cortisol)
- Hormonal contraceptives (estrogens/gestagens)
Interpretation of decreased values
- Hyperthyroidism (hyperthyroidism).
- Consumptive diseases such as cancer or chronic infections.
- Liver diseases such as cirrhosis – remodeling of liver tissue with loss of function.
- Malabsorption – disruption of the absorption (absorption) of food in the intestine.
- Malnutrition – malnutrition or malnutrition.
- Operations
- Protein deficiency (lack of protein)
Other notes
- Elevated serum cholesterol is one of the most important risk factors for atherosclerosis (hardening of the arteries). This in turn leads to a significantly increased risk of cardiovascular events such as myocardial infarction (heart attack) or apoplexy (stroke).
- At a total cholesterol above 200 mg / l is already an increased coronary risk!
- Total cholesterol and HDL cholesterol, when not fasting, vary by less than 2% (compared to a collective with fasting blood sampling). LDL cholesterol levels are altered by approximately 10% with a meal.
- HDL cholesterol:
- The relationship between HDL cholesterol (HDL-C) and the risk of coronary artery disease (CAD; coronary artery disease) is not linear; above an HDL-C of about 60 mg/dl (1.5 mmol/l), no further improvement in prognosis is seen.
- HDL levels above 60 milligrams/deciliter (1.5 mmo/L) had a nearly 50 percent increased risk of death or myocardial infarction from cardiovascular disease in one study.
- Studies show that very high levels of HDL-C may again be associated with an increase in CHD (coronary heart disease) risk.
Further laboratory diagnostics
The following lipid status is required to accurately assess risk:
- Total cholesterol, LDL cholesterol, HDL cholesterol (see above).
- Lipoprotein (a)
- Triglyceride
- Lipid electrophoresis
