Clinical diagnosis of dyslipidaemia
Increased levels of serum triglycerides and decreased HDL are the characteristic lipid results in people with type II diabetes and in those with impaired glucose tolerance. These lipid abnormalities are a major contributor to the increased risk of vascular disease in these patients and lipid-lowering treatment has a significant impact on morbidity and mortality. Regular assessment of lipid profile is therefore an important aspect of addressing vascular risk in people with diabetes.
Dyslipidaemia is often detected during routine screening of a patient with increased vascular risk and is commonly found in patients with diabetes. While diabetes is a major secondary cause of dyslipidaemia, it must be remembered that other forms of dyslipidaemia may co exist with diabetes. All modifiable risk factors for atherosclerosis must be addressed in the assessment of the patient with dyslipidaemia (smoking, hypertension, glycaemic control). Personal and family history of premature coronary heart disease should be assessed including relatives’ age of onset of coronary heart disease, lipid concentrations and smoking history. For deceased relatives, the age and cause of death, and smoking history is important. Any personal history of other vascular disease (cerebrovascular and/or peripheral vascular disease) should be noted.
Clinical stigmata of hyperlipidaemia should be documented. These include early onset of corneal arcus (age <50 years), xanthelasma around the eyes and tendon xanthomata (more specific sign of Familial Hypercholesterolaemia). Cardiovascular and peripheral vascular examinations should be performed along with baseline electrocardiogram to detect evidence of cardiac ischaemia.
It is essential to exclude other secondary causes of dyslipidaemia (see Classification of dyslipidaemia. Alcohol intake and drug history are vital because excess alcohol consumption and a variety of medications are associated with hyperlipidaemia. Obesity is a further major secondary cause of dyslipidaemia; dietary and exercise advice is important in the management of dyslipidaemia in combination with pharmacological measures. Assessment of renal, liver and thyroid function should also be undertaken.
Full lipid profile is clearly crucial to the diagnosis (Fasting vs non-fasting lipid samples). In the patient with diabetes, a fasting lipid profile is preferred. If there is suspicion of co-existing inherited hyperlipidaemia, then genetic testing may help in some patients (Genetic assessment of dyslipidaemia).