Cholesterol (T513) [Back]
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| RISK ASSESSMENT VALUE: |
This test, the quantitative analysis of serum cholesterol, measures the total circulating levels of free cholesterol and cholesterol esters. Cholesterol, a structural component in cell membranes and plasma lipoproteins, is both absorbed from the diet (10-20%) and synthesized (80%) in the liver. It is the parent compound for synthesis of steroid hormones, glucocorticoids, and bile acids. Both LDL and HDL are included in total cholesterol.
Higher cholesterol values are generally associated with higher atherosclerotic risk mainly because they are associated with higher LDL values. Studies in various populations suggest a 1% increase in total long term mortality for every 2 mg/dL increase in total cholesterol. This association in son valid if the elevation of total cholesterol is instead caused by an exceptionally high HDL component. Cholesterol rather than LDL is often used in calculating cardiac risk because, unlike LDL, it is a directly measured value and unaffected by fasting state which is difficult to confirm in the insurance setting. See Cholesterol/HDL ratio.
One limitation in all lipid results is the high test to test variability much of which reflects biologic variability over time and some reflects the precision of testing which is lower for lipids than for some chemistries. If multiple values are available, better risk selection is obtained by averaging them.
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| NORMAL RESULTS: |
Statistical normal range:
Female 120 - 260 mg/dL
Male 140 - 280 mg/dL
Optimal values (assuming average HDL levels) are < 200 with unfavorable values being > 240 mg/dL.
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| ABNORMAL RESULTS: |
Values above 240 mg/dL are typically associated with higher LDL levels and higher long term mortality risk.
Values at the lower end or the normal range in older adults are associated with excess mortality but the cause of this association is most likely concurrent illness even if not recognized clinically. This association also holds true for insurance applicants but it is unknown if it also exist in those actually issued life insurance.
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| ADDITIONAL TESTS: |
HDL and Cholesterol/HDL ratio
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| SAMPLE NEEDED: |
Separated serum from a red-stopper tube or dried blood spot.
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| SAMPLE STABILITY: |
10 days at room temperature; 2 weeks when refrigerated; indefinitely when frozen.
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| METHOD & INSTRUMENT: |
Cholesterol esters present in serum or plasma are hydrolyzed quantitatively into free cholesterol and fatty acids by microbial cholesterol esterase, Hitachi 717, 736, 747
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| INTERFERING FACTORS: |
None, but day to day biologic variability of all lipid values is high. Averaging values on different days should be used for risk assessment if values are available.
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| PURPOSE: |
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| PROFILE INCLUDES: |
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| RISK RANGE & UNITS: |
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