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HannuVanhanen
TimoStrandberg

Definition and Diagnosis of Dyslipidaemias

Essentials

  • Dyslipidaemias increase the total risk of arterial disease significantly; the aim of treatment is to decrease the risk.
  • On a population level, the main health-promoting lipid values are total plasma cholesterol below 5.0 mmol/l and LDL cholesterol below 3.0 mmol/l.
  • Lipid levels should be measured:
    • in patients with arterial disease (coronary artery disease, cerebral artery disease, arteriosclerosis obliterans (ASO)), diabetes or renal failure
    • in asymptomatic people with an increased risk of arterial disease according to a locally relevant risk calculator
    • in young adults with a single significant risk factor or early-onset arterial disease in the family
    • otherwise in men by 40 years of age, at the latest, and in women by 50 years of age or by menopause, at the latest.
  • Efforts should be made to identify familial hypercholesterolaemia in patients and their family (indication for consultation of specialized care).
  • Secondary dyslipidaemia, most often due to (even subclinical) hypothyroidism, should be identified.
  • Screening lipid levels in the whole population is not the primary means of preventing arterial disease. Instead, the emphasis should be on general promotion of a healthy diet and lifestyle, complemented by action in the community (e.g. in canteens, sports facilities, etc.).

Diagnosis

  • Definition of dyslipidaemia
    • Plasma LDL cholesterol level exceeding 3.0 mmol/l or
    • triglyceride level exceeding 1.7 mmol/l or
    • HDL cholesterol level below 1.0 in men or 1.2 mmol/l in women.
  • One test is not sufficient to give a reliable idea of plasma lipid levels: test cholesterol, HDL cholesterol, LDL cholesterol and triglycerides twice.
    • Fasting is usually of minor significance for lipid tests.
      • Meals have little effect on total cholesterol levels.
      • A meal will raise triglyceride levels by about 0.3 mmol/l, if the plasma triglyceride level is < 5 mmol. If the level is higher, measure the fasting value.
    • LDL and HDL cholesterol levels are today measured by a direct method.
      • If no direct method is available, calculate using the Friedewald formula (Calculator Ldl).
    • The target level for LDL cholesterol depends on the total risk of arterial disease, see Table Treatment of Dyslipidaemias.
  • Other tests (in special cases)
    • Non-HDL cholesterol (= total cholesterol minus HDL cholesterol)
      • Shows the concentration of all atherogenic lipoproteins (VLDL, IDL and LDL).
      • Can be used whenever triglyceride levels are elevated or LDL cholesterol cannot be determined.
      • The treatment goals are 0.8 mmol/l higher than the respective LDL cholesterol levels.
    • Lipoprotein (a)
      • A lipoprotein(a) level exceeding 500 mg/l is a risk factor for atherosclerosis.
      • The distribution is skewed due to very high levels detected rarely.
      • Testing once may be indicated to investigate a strong hereditary predisposition to arterial disease or if LDL levels do not fall as expected despite statin treatment.
    • The significance of testing apolipoproteins (apoB, apoA1) is limited by the lack of standardization of the test methods.

Common hypercholesterolaemia

  • The most common form of dyslipidaemia
  • A combined effect of diet, excessive energy intake (obesity) and hereditary predisposition

Secondary dyslipidaemias

  • Consider whether elevated lipid levels could be due to some other treatable disease (Table T1) or drug (Table T2).
    • Of these, hypothyroidism is the most important cause.

Causes of secondary dyslipidaemia

HypercholesterolaemiaHypertriglyceridaemiaHypercholesterolaemia + hypertriglyceridaemia
Hypothyroidism
Nephrotic syndrome
Cholestasis
Anorexia
Acute intermittent porphyria
Hypopituitarism
Alcohol
Overweight
Insulin resistance
Diabetic ketosis
Type 2 diabetes
Uremia
Cushing's syndrome
Paraproteinaemia
Hypothyroidism
Nephrotic syndrome
Liver disease
(Type 2 diabetes)
  • Note that pregnancy may elevate plasma cholesterol and triglyceride levels significantly.
  • Acute myocardial infarction and infections lower the levels transiently.

Drugs affecting lipids

DrugEffect on lipids
Anabolic steroidsLower HDL levels greatly.
Antipsychotic drugs (e.g. quetiapine, clozapine, olanzapine, paliperidone and risperidone)May elevate lipid levels (most often triglycerides).
Certain HIV drugsElevate triglyceride levels.
IsotretinoinMay elevate triglyceride levels and lower HDL levels.
Oral oestrogen, tamoxifen, antiandrogen therapyMay cause dyslipidaemia.
Glucocorticoids, ciclosporin, several anticancer drugsMay cause dyslipidaemia.

Familial hypercholesterolaemia (FH)

  • Autosomal dominant inheritance
    • Estimated prevalence: 1:500 and 1:1 000 000 for heterozygous and homozygous FH, respectively (estimates vary by source)
  • Suspect FH in an adult with:
    • plasma cholesterol 8 mmol/l (LDL 5 mmol/l) or
    • early-onset coronary artery disease (men < 55 years, women < 60 years) in the patient or a first-degree relative or
    • early sudden cardiac death of a first-degree relative or
    • tendinous xanthomas in the patient or a first-degree relative.
  • The clinical probability of FH can be classified based on Dutch Lipid Clinic Network scoring http://www.mdcalc.com/dutch-criteria-familial-hypercholesterolemia-fh.
  • Typical clinical pictures include:
    • tendinous xanthomas in Achilles tendons, knees and finger extensor tendons
    • arcus lipoides and xanthelasmas (Picture 1).

Familial combined dyslipidaemia

  • Is fairly common.
  • Increases the risk of arterial disease as much as common dyslipidaemia of an equivalent level.
  • Family history of arterial disease is common.
  • Typically both cholesterol and triglycerides, as well as the apoB concentration, are elevated.

Other hereditary dyslipidaemias

Hypertriglyceridaemia

  • Mild hypertriglyceridaemia (2.0-5.0 mmol/l) is often only a result of genetic and environmental factors in combination with lifestyle factors (overweight, alcohol) or with poor glycaemic control in patients with diabetes.
  • About 1% of the population have autosomal dominantly inherited primary hypertriglyceridaemia.
  • Greatly elevated triglyceride levels (> 5-10 mmol/l) carry a risk of pancreatitis and eruptive xanthomatosis. Some patients have joint symptoms that may be due to gout.

Metabolic syndrome

  • Metabolic syndrome is a cluster of risk factors significantly increasing the risk of arterial disease and diabetes; see Metabolic Syndrome.
  • Metabolic syndrome involves:
    • increased waist circumference
    • elevated triglyceride levels
    • low HDL levels
    • hypertension
    • elevated fasting glucose levels.

Risk calculators

Workup in patients with lipid levels requiring treatment

History

  • Family history of atherosclerotic disease and any known cholesterol levels
  • Diagnosis or symptoms of arterial disease or findings suggesting arterial calcification in previous imaging studies
  • Smoking, dietary and exercise habits, alcohol consumption, weight development in overweight patients

Clinical exam

  • Blood pressure
  • Auscultation of the heart and large arteries
  • Doppler stethoscopy of the lower limbs if there is reason to suspect ASO Doppler Stethoscopy in Diagnostics
  • Inspection of the skin for any tendinous xanthomas or xanthelasmas (particularly in the Achilles tendon region or around the eyes)
    • If FH is suspected, ultrasonography may show Achilles tendon xanthomas.

Laboratory tests

  • Cholesterol, HDL cholesterol, LDL cholesterol and triglycerides
  • ALT, creatinine (GFR Gfr Calculator)
  • Fasting plasma glucose and HbA1c (diabetes)
  • Chemical urinalysis, urine albumin/creatinine ratio (proteinuria)
  • TSH as necessary

References

  • Mach F, Baigent C, Catapano AL et al. 2019 ESC/EAS Guidelines for the management of dyslipidaemias: lipid modification to reduce cardiovascular risk. Eur Heart J 2020;41(1):111-188. [PubMed]
  • Piepoli MF, Hoes AW, Agewall S et al. 2016 European Guidelines on cardiovascular disease prevention in clinical practice: The Sixth Joint Task Force of the European Society of Cardiology and Other Societies on Cardiovascular Disease Prevention in Clinical Practice (constituted by representatives of 10 societies and by invited experts)Developed with the special contribution of the European Association for Cardiovascular Prevention & Rehabilitation (EACPR). Eur Heart J 2016;37(29):2315-2381. [PubMed]
  • Wilkins JT, Ning H, Berry J et al. Lifetime risk and years lived free of total cardiovascular disease. JAMA 2012;308(17):1795-801. [PubMed]
  • Gooding HC, Ning H, Gillman MW et al. Application of a Lifestyle-Based Tool to Estimate Premature Cardiovascular Disease Events in Young Adults: The Coronary Artery Risk Development in Young Adults (CARDIA) Study. JAMA Intern Med 2017;177(9):1354-1360. [PubMed]
  • Alberti KG, Eckel RH, Grundy SM et al. Harmonizing the metabolic syndrome: a joint interim statement of the International Diabetes Federation Task Force on Epidemiology and Prevention; National Heart, Lung, and Blood Institute; American Heart Association; World Heart Federation; International Atherosclerosis Society; and International Association for the Study of Obesity. Circulation 2009;120(16):1640-5. [PubMed]