Causes of Lipemic Blood Samples
A lipemic blood sample results primarily from elevated triglyceride-rich lipoproteins in plasma, most commonly due to postprandial lipemia (recent fatty meal intake) or pathological hypertriglyceridemia from metabolic disorders. 1
Primary Causes
Postprandial (Non-Fasting) State
- Recent fatty meal consumption is the most common cause of lipemic samples in clinical practice, occurring when elevated numbers of lipoproteins are present after eating, causing plasma to lose its transparency and appear milky or opaque 1
- Donors who consume a fatty meal before blood collection demonstrate increased plasma triglyceride concentrations for several hours, directly contributing to the milky-white appearance 2
- The postprandial state elevates chylomicrons (triglyceride-rich lipoproteins produced by the intestine that transport dietary lipids), which are the largest lipoprotein particles and create visible turbidity 1, 3
Pathological Hypertriglyceridemia
Familial/Genetic Disorders:
- Lipoprotein lipase (LPL) deficiency (familial type I hyperlipoproteinemia) causes severe lipemia with triglyceride-to-cholesterol ratios of 10:1 and triglycerides >1000 mg/dL, presenting with lipemia retinalis, hepatosplenomegaly, and eruptive xanthomas 1
- Apolipoprotein C-II deficiency produces similar severe chylomicronemia due to absence of the cofactor needed for LPL function 1
- Familial combined hyperlipidemia (FCHL) results from hepatic overproduction of apoB-containing VLDL, IDL, and LDL particles 1
- Type III dysbetalipoproteinemia and familial hypertriglyceridemia (FHTG) also cause elevated triglyceride-rich lipoproteins 1
Secondary Metabolic Conditions:
- Diabetes mellitus (particularly poorly controlled Type 1 or Type 2) causes elevated VLDL triglycerides and reduced HDL-cholesterol, with Type 2 diabetes often accompanied by high triglyceride levels and smaller cholesterol ester-depleted LDL particles 1
- Chronic kidney disease produces dyslipidemia with triglyceride levels ≥200 mg/dL in 50% of patients, especially pronounced in nephrotic syndrome and peritoneal dialysis 1
- Pregnancy physiologically increases triglycerides, total cholesterol, HDL-C, and LDL-C, with women having pre-pregnancy overweight/obesity showing significantly higher concentrations that can exceed the physiological range 1
- Obesity and metabolic syndrome are associated with hypertriglyceridemia driven by elevated triglyceride-rich lipoproteins like chylomicrons and VLDL 1
Lipoprotein Composition in Lipemic Samples
The lipemic appearance reflects specific lipoprotein particles:
- Chylomicrons (largest particles, 75-1200 nm diameter) transport dietary lipids and contain apolipoprotein B-48 1, 3
- Very low-density lipoproteins (VLDL) (30-80 nm diameter) are secreted by the liver and contain apolipoprotein B-100 1, 3
- These triglyceride-rich lipoproteins are by far the most abundant colloid particles in blood when elevated, classified by density and size with specific apolipoprotein compositions 1
Important Clinical Pitfalls
Distinguish lipemia from other plasma discoloration:
- Hemolysis produces orange or red plasma due to disrupted red blood cell membranes releasing hemoglobin, typically from poor venipuncture or excessive vacuum in collection tubes 1
- Normal plasma is clear and transparent yellow fluid 1
- Clotted samples appear turbid and non-transparent as a gel when anticoagulation is insufficient, with fibrinogen converting to insoluble fibrin polymers 1
Competition for lipolytic pathways:
- Elevated chylomicrons impede normal lipolytic degradation of VLDL through competition for the same lipolytic pathway (lipoprotein lipase), causing accumulation of large VLDL particles and potentially generating atherogenic remnant lipoproteins 4
- This explains why postprandial lipemia can cause accumulation of both chylomicrons and VLDL particles simultaneously 4
Severe hypertriglyceridemia (>1000 mg/dL) requires urgent attention due to risk of acute pancreatitis, which can lead to chronic pancreatitis or death 1