Diabetes Testing Flashcards
What tests your plasma glucose?
3
- Fasting plasma glucose (FPG)
- Random plasma glucose (RPG)
- Two-hour plasma glucose during an oral glucose tolerance test (2-h OGTT)
What is the normal FPG?
Increased risk for Diabetes “Pre-diabetes”:
Impaired fasting glucose?
Impaired glucose tolerance?
Diabetes Mellitus: Hem A1C ? FPG ? 2h OGTT ? Symptomatic hyperglycemia RPG ?
Normal: FPG is less than 100mg/dL
Impaired fasting glucose (IFG): 100-125
Impaired glucose tolerance (IGT): 2h OGTT of 140-199
Diabetes Mellitus: Hem A1C ≥ 6.5% FPG ≥ 126 2h OGTT ≥ 200 Symptomatic hyperglycemia RPG ≥ 200
**Critical Note: Diagnosis must be confirmed on a subsequent day by measuring any one of the criteria
What is the sensitivity and specificity of the 126 level if using the 2h OGTT ≥ 200 as the reference standard?
Specificity > 95 percent (the ability to rule it in)
Sensitivity about 50% (the ability to rule it out)
In other words, a person that has an FPG of 126 or higher highly likely has diabetes, but a person with a level of, let’s say 120, may still have diabetes when using the 2h OGTT criteria as a reference
Factors that affect blood sugar?
3
Medications
Emotional stress
Physical stress
_____released during stress increase blood sugar.
What kind of stress? 5
Hormones
Physical or emotional stress
- Surgery
- Infection
- Stroke
- MI
- Emotional stress and anxiety
What can elevate blood sugar other than diabetes, IFG, or IGT?
8
- Medications
- Stress hyperglycemia
- Cushing’s syndrome,
- acromegaly,
- pheochromocytoma,
- glucagonoma,
- liver disease,
- pancreatitis
What meds can elevate blood sugar?
4
Steroids
Beta-blockers
Nicotinic acid
Estrogens
Recommendations For Diabetes Screening?
3
- FPG screening every 3 years beginning at age 45 years
- Consider screening at an earlier age (or more frequently if >45yo) if diabetes risk factors are present
- BMI ≥ 25 + 1 or more risk factors
What are the screening tests?
If tests are normal then when should you retest?
- A1C,
- fasting plasma glucose,
- 2 h oral glucose tolerance test
If the tests are normal do it again in three years
DM Risk factors - review
14
- Age ≥ 45
- BMI ≥ 25
- FmHx of DM in a 1st degree relative
- Hx of gestational DM
- High risk ethnicity (African 6. American, Hispanic, Native American, Asian American, Pacific Islanders)
- Hypertension
- HDL less than 35
- Triglycerides ≥ 250
- A1C ≥ 5.7
- Polycystic ovarian syndrome
- Vascular disease
- Sedentary lifestyle
- IFG/IGT
For the diagnosis of diabetes ______ are necessary.
What is not recommended? 2
plasma samples
- Point of care testing for A1C is not recommended for diagnosis
- Finger stick blood glucose is not used for diagnosis
Why do we not use fingerstick for diagnosis?
2
- Venous glucose levels may be higher than capillary levels
For fasting samples and random testing (FPG) - Venous glucose levels lower than capillary
2 h after oral glucose load
AT what levels for FPG do we diagnose as DM?
ANything lower than this value we treat as what?
126 or over.
Anything lower than that and we treat it as impaired fasting glucose
(need two tests)
At what level for random glucose testing do we diagnose diabetes?
What do we follow it up with before we determine the diagnosis?
over 200
FPG
(If the RPG is 200 but FPG is less than 126 then we still treat as IFG)
The _______ is a way to measure the mean glucose level over 3 months. How does it do this? 3
hemoglobin A1C
- Hemoglobin that is formed in new red blood cells enters the circulation without any glucose attached
- Red cells are freely permeable to glucose
- Glucose becomes irreversibly attached to hemoglobin at a rate dependent upon the prevailing blood glucose
(What percent of your red blood cells are coated in sugar)
Hemoglobin A1C correlates best with mean blood glucose over what period of time?
Correlates best with mean blood glucose over the previous 8 to 12 weeks.
Hemoglobin A1C
sources of error?
2
- red blood cell turnover is low (delayed) = flasely high A1Cs
- rapid red cell turnover leads to a greater proportion of younger red cells and falsely low A1C values.
Factors that may alter A1C results:
Increase? 6
Decrease? 4
Increase:
- Iron deficiency anemia
- Alcohol toxicity
- Lead toxicity
- Late pregnancy due to the iron deficiency anemia
- Genetic variants
- Hgb S, Hgb C traits
Decrease:
- Hemolytic anemia
- Chronic blood loss
- Pregnancy
- Chronic renal failure