fasting specimen

fasting specimen

Lab medicine A blood specimen drawn from a Pt who has not eaten for 12 hrs; fasting is an absolute requirement for a limited number of tests–eg, GTT; prolonged fasting causes a marked–240% ↑ in bilirubin, ↑ plasma TGs, glycerol and free fatty acids, and a marked–± 50% ↓ in glucose. See Glucose tolerance test.
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Serum testosterone should be checked on a first-morning fasting specimen. Low testosterone concentrations need to be confirmed before making the diagnosis and should be followed by checking FSH and LH.
In contrast, the 2013 guidelines released by the American College of Cardiology/American Heart Association (ACC/AHA) preferred a fasting specimen for lipid testing.
The first subquestion asks, "What is the basis for basal-state fasting for 10 to 12 hours?" A basal-state lipid profile fasting specimen determined by fasting overnight for nine to 12 hours is recommended for collection of a specimen for measurement of the lipid profile of total cholesterol, triglyceride, and HDL cholesterol, mainly because of the highly variable triglyceride diurnal variation.
Because nonfasting specimens often contain traces of chylomicrons, calculation requires a fasting specimen (ideally >12 h).
We collect the specimen early in the day to get as close to a fasting specimen as possible.
Fasting specimens must be collected after a 10- to 12-hour complete dietary restriction of everything except water and medications.
Triglyceride values are also used to calculate LDL cholesterol (LDL-C) by difference using the Friedewald equation, which was derived using fasting specimens. Hence, the equation might require revision and validation for specimens collected under nonfasting conditions.
Obtaining SPLs only on fasting specimens can help improve test accuracy.
Our study was designed to determine the magnitude of changes induced by deviating from the recommended and standardized procedures of collecting fasting specimens early in the morning.
The Friedewald formula provides an adequate estimate of LDL-cholesterol for most fasting specimens but is known to be less reliable as triglyceride concentration increases [5].
With plasma, only fasting specimens should be used for assessing AA status.