Diabetes Testing Flashcards
What are the tests used for diabetes testing?
- fasting plasma glucose
- random plasma glucose
- two hour plasma glucose during an oral glucose tolerance test
- glycosylated hemoglobin (hgA1C)
- Fructosamine
- Urine dipstick testing
- self monitoring blood glucose
- continuous glucose monitoring
Plasma Glucose values
normal (FPG)
Pre-diabetes (IFG, IGT)
DM (A1C, FPG, OGTT, RPG)
normal: FPG less than 100 mg/dL
Pre-diabetes:
- impaired fasting glucose: 100-125
- impaired glucose tolerance: 2h OGTT of 140-199
DM:
- A1C: less than or equal to 6.5%
- FPG greater than or equal to 126
- 2h OGTT greater than or equal to 200
- symptomatic hyperglycemia RPG greater than or equal to 200
**dx MUST be confirmed on a subsequent day by measuring any one of the following criteria
Plasma glucose-
specificity
sensitivity
specificity: more than 95% (the ability to rule in)
sensitivity: about 50% (the ability to rule out)
meaning- if a person has a positive test, they likely have DM. If a person has a negative test, they may still have DM
Factors that affect blood sugar
What do hormones do during stress?
- medications (beta blockers, nicotinic acid, estrogens)
- emotional stress
- physical stress (surgery, infection, stroke, MI)
- Stress hyperglycemia** (also called stress diabetes or diabetes of injury) is a medical term referring to transient elevation of the blood glucose due to the stress of illness. It usually resolves spontaneously
- Cushings, acromegaly, pheochromocytoma, etc.
During stress, hormones increase blood sugar as part of the flight or fight response
What are the ADA recommendations for screening?
- FPG screening every 3 years beginning at age 45 for people without risk factors
- consider screening earlier or more frequently if DM risk factors are present
DM risk factors
- age >45
- BMI > 25
- fmHX of DM
- Hx of gestational DM
- race (african american, hispanic)
- HTM
- HDL less than 35
- Tg greater than 250
- A1C greater than 5.7
- PCOD
- Sedentary lifestyle
- IFG/IGT
What type of samples are necessary for the dx of DM?
PLASMA samples
- point of care testing is not recommended
- finger stick blood glucose is not used for dx
Why is a finger stick not used for dx?
venous glucose levels may be higher than capillary levels for fasting samples and random testing
venous levels may be lower than cap 2h after oral glucose load
Glycosylated Hemoglobin (Hemoglobin A1C)
- what does it measure?
- how/why does it work?
- levels for normal, abnormal, diabetes
- measures the mean glucose level over 3 months
- Hb that is formed in new rbcs enters the circulation without any glucose attached… rbcs are freely permeable to glucose… glucose becomes irreversibly attached to hb at a rate dependent upon the prevailing blood glucose
- normal less than 5.7%
- abnormal 5.7-6.4%
- diabetes greater than 6.5%
Sources of Error for Hb A1C
*A1C is influenced by red cell survival!
- when rbc turnover is low (iron, B12, folate deficiency anemia), A1C can be falsely HIGH
- when rbc turnover is rapid (hemolysis, pregnancy), A1C can be falsely low
When to test A1C
- if meeting DM treatment goals, twice yearly
- if not meeting goals or medication change, test every 3 months
Fructosamine
- tells you how many weeks of average blood glucose control?
- when would values need to be adjusted?
- when is this test useful?
- shows 1-2 weeks of average blood glucose control
- if albumin level is abnormal, fructosamine values mist be adjusted (falsely low levels with rapid albumin turnover)
- useful in any change in treatment instead of waiting 3 months to have a test or to avoid frequent sticks
Urine Glucose
- what does glucose in the urine mean?
- where is glucose typically reabsorbed?
-glucose in the urine signifies that the filtered load is exceeding the absorptive capability of the proximal tubule
(blood glucose levels at which glucose appears in the urine varies, but usually greater than 180)
-Usually, all the glucose is reabsorbed at the proximal tubule
How are ketones produced?
When do do ketones levels increase?
MOre common in what type of diabetes?
Are there ketones in the serum and urine normally?
Ketones are produced in the liver as part of fatty acid metabolism.
Ketones increase when not enough insulin to use glucose for energy
more common in Type 1 because there is no insulin to be used
There are normally small amounts of ketones present in the serum and urine but are not detectable by conventional testing, so a positive test for ketones indicated considerable excess in the blood
Why MIGHT a pt with DKA have urine negative for ketones?
- If severe renal insufficiency exists, kidneys may be unable to filter ketones.
- tests react strongly to acetoacetic acid, but not beta-hydroxybutyrate. In DKa, most of the ketones are in the form of beta-hydroxybutyrate
