numerous factors that occur before a sample is measured can influence results of blood tests. Examples include medications, venous stasis, position, and sample distribution handling. The concentration of glucose in the blood can be altered by food consumption, prolonged fast, or drill ( 8 ). It is besides important that measurements are performed in subjects in the absence of intercurrent illness, which frequently produces ephemeral hyperglycemia ( 9 ). similarly, acute try ( for example, not being able to find parking or having to wait ) can alter blood glucose concentrations.
Samples for fasting glucose analysis should be drawn after an overnight fast ( no thermal consumption for at least 8 planck’s constant ), during which clock the topic may consume water ad lib ( 10 ). The necessity that the capable be fast is a considerable practical trouble as patients are normally not fasting when they visit the sophisticate, and it is frequently inconvenient to return for venesection. For exemplar, at an HMO affiliated with an academician medical center, 69 % ( 5,752 of 8,286 ) of eligible participants were screened for diabetes ( 11 ). however, FPG was performed on only 3 % ( 152 ) of these individuals. ninety-five percentage ( 5,452 ) of participants were screened by random plasma glucose measurements, a technique not reproducible with ADA recommendations. In addition, rake draw in the good morning as FPG has a diurnal variation. analysis of 12,882 participants aged 20 years or older in NHANES III who had no previously diagnosed diabetes revealed that mean FPG in the dawn was well higher than in the good afternoon ( 12 ). prevalence of diabetes ( FPG ≥126 mg/dL ) in afternoon-examined patients was half that of participants examined in the dawn. other patient-related factors that can influence the results include food consumption when supposed to be fasting and hypocaloric diet for a workweek or more prior to testing.
Read more: Gastritis – Symptoms and causes
Glucose concentrations decrease in the test tube by 5–7 % per hour due to glycolysis ( 13 ). therefore, a sample distribution with a on-key blood glucose measure of 126 mg/dL would have a glucose concentration of ∼110 mg/dL after 2 planck’s constant at board temperature. Samples with increased concentrations of erythrocytes, white blood cells, or platelets have even greater rates of glycolysis. A coarse misconception is that sodium fluoride, an inhibitor of glycolysis, prevents glucose consumption. While fluoride does attenuate in vitro glycolysis, it has no effect on the rate of decay in glucose concentrations in the first 1 to 2 h after blood is collected, and glycolysis continues for up to 4 planck’s constant in samples containing fluoride ( 14 ). The delay in the glucose stabilizing impression of fluoride is most likely the solution of glucose metamorphosis proximal to the fluoride target enolase ( 15 ). After 4 hydrogen, fluoride maintains a stable glucose concentration for 72 h at board temperature ( 14 ). A holocene issue showed that acidification of the blood sample inhibits glycolysis in the beginning 2 henry after venesection ( 16 ), but the collection tubes used in that study are not commercially available. Placing tubes in ice rink urine immediately after collection may be the best method to stabilize glucose initially ( 2, 16 ), but this is not a practical solution in most clinical situations. Separating cells from plasma within minutes is besides effective, but impractical .
The nature of the specimen analyzed can have a big influence on the glucose concentration. Glucose can be measured in unharmed blood, serum, or plasma, but plasma is recommended by both the ADA and World Health Organization ( WHO ) for diagnosis ( 1, 2 ). however, many laboratories measure glucose in serum, and these values may differ from those in plasma. There is a miss of consensus in the publish literature, with glucose concentrations in plasma reported to be lower than ( 17 ), higher than ( 16, 18, 19 ), or the same as ( 20 ) those in serum. importantly, glucose concentrations in solid blood are 11 % lower than those in plasma because erythrocytes have a lower water content than plasma ( 13 ). The magnitude of the difference in glucose between wholly blood and plasma changes with hematocrit. Most devices ( normally handheld meters ) that bill glucose in capillary blood use hale blood. While the majority of these report a plasma equivalent glucose value ( 21 ), this leave is not accurate in patients with anemia ( 22 ) ( unless the meter measures hematocrit ) .
The beginning of the blood is another variable. Although not a substantial problem in the fast state, capillary glucose concentrations can be 20–25 % higher ( mean of 30 mg/dL ) than venous glucose during an OGTT ( 23 ). This find has practical implications for the OGTT, particularly because the WHO deems capillary blood samples satisfactory for the diagnosis of diabetes ( 2 ) .