Diabetes testing

Question 1

Levels of plasma glucose?

Answer 1

• normal: FPG: less than 100 mg/dL
• increased risk for diabetes “pre-diabetes”:
  impaired fasting glucose (IFG) - 100-125
  impaired glucose tolerance (IGT) - 2 hr OGTT 140-199
• DM:
  A1C greater or equal to 6.5%
  FPG greater or equal to 126
  2 hr OGTT is greater or equal to 200
• sx hyperglycemia RPG greater or equal to 200

*** dx must be confirmed on a subsequent daby by measuring any one of the criteria

Question 2

What is the sensitivity and specificity of 126 level if usuing the 2 hr OGTT greater or equal to 200 as a reference standard?

Answer 2

• specificity: greater than 95% (ability to rule in)
  sensitvity about 50% (ability to rule it out)
• a person that has a FPG of 126 or higher highly likely to have diabetes but a person with level of 120 may still have diabetes when using 2 h OGTT criteria as reference

Question 3

What factors affect blood sugar?

Answer 3

• medications
• emotional stress
• physical stress

Question 4

When are hormones relesased to increase blood sugar?

Answer 4

• in times of stress
• part of fight or flight response
• physical or emotional stress: surgery, infection, stroke, MI, emotional stress and anxiety

Question 5

What can elevated blood sugar other then diabetes, IFG, or IGT?

Answer 5

meds: **steroids, beta-blockers, nicotinic acid, and estrogents
- **stress hyperglycemia: usually seen in acutely ill pt
- others: cushing’s syndrome, acromegaly, pheochromocytoma, glucagonoma, liver disease, and pancreatitis

Question 6

What are the ADA recommendations for screening?

Answer 6

• FPG screening every 3 years beginning at age 45 years
• consider screening at an earlier age ( or more frequently if older than 45) if diabetes risk factors are present
• w/o risk factors: can start to screen all persons age 45 and older
• BMI greater or equal to 25 + 1 or more risk factors
• screening tests: A1C, fasting plasma glucose, 2 hr OGTT
• if normal (A1C less than 5.7, FPG less or equal to 100) retest in 3 years

Question 7

Risk factors of DM?

Answer 7

• age: greater or equal to 45
• BMI: greater or equal to 25
• FmHx of DM in 1st degree relative
• Hx of gestational DM
• high risk ethnicity (African american, hispanic, native american, asian american, pacific islanders)
• HTN
• HDL less or equal to 35
• TGs greater or equal to 250
• A1C greater or equal to 5.7
• PCOS
• vascular disease
• sedentaray lifestyle
• IFG/IGT

Question 8

What should be done for dx of diabetes?

Answer 8

• plasma samples
• point of care testing for A1C not recommended for dx
• finger stick blood glucose isn’t used for dx
• if significantly elevated finger stick glucose - draq a serum sample to confirm

Question 9

Difference b/t fingerstick vs plasma glucose?

Answer 9

• venous glucose levels may be higher than capillary levels : for fasting samples and random testing
• venous levels lower than capillary: 2 hr after oral glucose load

Question 10

What is the A1C measuring?

Answer 10

• plasma glucose only gives us snapshot in time. In reality there are many fluctuations with blood sugar throughout the day
• the hemoglobin A1C is way to measure the mean glucose level over 3 months.
• hemoglobin that is formed in new RBCs enters circulation without any glucose attached
• RBCs are freely permeable to glucsoe
• glucose becomes irreversibly attached to heomoglobin at a rate dependent upon prevailing blood glucose
• correlates best with mean blood glucose over the previous 8 to 12 weeks

Question 11

How was mean glucose levels measured before the A1C?

Answer 11

• est. with frequent blood glucose levels during the day:
  before and 90 minutres after:
  breakfast, lunch, dinnerand at bedtime
  (7 sticks per day)

Question 12

Hemoglobin values?

Answer 12

• greater or equal to 6.5% diabetes
• 5.7-6.4% abnormal
• less than 5.7% is normal

Question 13

Sources of error in A1C?

Answer 13

• A1C values are influenced by A1C survival
• whe RBC turnover is low (delayed) such as with iron, vitamin B12, or folate deficiency anemia, there are a disproportionate number of older RBCs which can lead to falsely high values
• In rapid cell turnover leads to greater proportion of younger RBCs and falsely low A1C values. Examples include pts with hemolysis and those tx for iron, Vit B12, or folate deficiency

Question 14

Whta are factors that could increase an A1C?

Answer 14

• iron deficiency anemia
• alcohol toxicity
• lead toxicity
• late pregnancy due to iron deficiency anemia
• genetic variants: Hgb S, Hgb C traits

Question 15

What are factors that could decrease A1C?

Answer 15

• hemolytic anemia
• chronic blood loss
• pregnancy
• chronic renal failure

Question 16

How often should a routine hemoglobine A1C be done?

Answer 16

• at least 2x yearly if meeting DM tx goals (usually around 7)
• test q 3 months if previous medication change or not meeting tx goals

Question 17

What is a fructosamine test and when is it useful?

Answer 17

• many proteins other than hemoglobin also undergo glycosylation
• 1-2 weeks of avg blood glucose control
• serum sample needed
• not very widely used

Question 18

What should be considered when doing a fructosamine test?

Answer 18

• if albumin level is abnormal than fructosamine values must be adjusted, falsely low levels with rapid albumin turnover
• increased vit C or hyperthyroidism can interfere with fructosamine levels
• may be useful if you want to know more recent blood sugars, don’t have to wait 3 months and also more accurate in pregnant, anemic, blood loss, abnorm RBCs: sickle cells (not measuring RBCs - hemoglobin)

Question 19

What do you measure in the urine?

Answer 19

• glucose
• ketones
• proteins

Question 20

Urine glucose significance

Answer 20

• glucose in blood is normally filtered at glomerulus with almost complete reabsorption taking place in proximal tubule
• glucose in urine signifies that filtered load is exceeding the absorptive capability of proximal tubule- it will continue on to collecting duct and show on the urine dipstick
• blood level at which glucose appears in urine varies from individual to individual, but usually occurs at levels greater than 180 mg/dL

Question 21

WHat is glucosuria?

Answer 21

noted when blood glucose exceeds 180

• leads to osmotic diuresis
• overall this isn’t normal, and needs a follow up blood sugar

Question 22

Ketones in urine?

Answer 22

• produced in liver
• part of fatty acid metabolism
• increase when not enough insulin to use glucose for energy
• more common in type 1 because there isn’t any insulin so breaking down fatty acids into ketones (DKA)

Question 23

What are the 3 types of ketones?

Answer 23

• beta-hydroxybutrate (in DKA most are in this form)
• acetoacetate
• acetic acid
• there are normally small amts of ketones present in serum and urine (which are not detected by conventional testing)
• positive test for ketones indicates considerable excess in the blood

Question 24

Urine ketones and DKA?

Answer 24

• in a pt with DKA, urine may be negative for ketones if severe renal insufficiency exists (kidneys may be unable to filter ketones)
• test reacts strongle to acetoacetic acid but not with beta-hydroxybutyrate. In DKA most of ketones present are in the form of beta-hydroxybutyrate (negative or weakly positive urine ketone shouldn’t sway clinician from possibility of ketoacidosis if presentation is suggestive

Question 25

- where else might you see ketonuria in absence of DKA?

Answer 25

- in low carb diets, starvation or vomiting

Question 26

When should you test

Answer 26

- pregnancy - elevated blood sugars greater than 300 - when suspicious for DKA

Question 27

When will ketones be detectable in the urine?

Answer 27

- poorly controlled DM - DKA - starvation - strict Atkins diet - poisoning - certain types of anesthesia - alkalosis - some metabolic disorders

Question 28

When will ketonuria be false positive?

Answer 28

- meds: levodopa, phenazopyrine, and valproic acid | - Vit C

Question 29

What is albuminuria?

Answer 29

- show up on regular urine dipstick as + for protein needs to be greater or equal to 300 mg (proteinuria) - moderately increased albuminuria (microabluminuria) albumin excretion 30-300 mg/g

Question 30

Screening for albuminuria?

Answer 30

- 5 years after dx of type 1 - upon dx of type 2 - then annually for all diabetics

Question 31

What is an albumin to creatinine ratio (ACR)?

Answer 31

- spot urine albumin/creatinine ratio: preferably first morning void, correlates well with 24 hr urine sample, microalbuminuria = 30-300 mg albumin/g of creatinine - 24 h urine collection is the std

Question 32

Dx of diabetic nephropathy?

Answer 32

- confirm a positive result with additional tests over next 3-6 months - 2 out of 3 samples that are abnormal within 6 month period = diabetic nephropathy

Question 33

Why should SMBG be done?

Answer 33

- to maintain good glucose control - allow adjustments of insulin and diet content to be made based on immediate feedback of glucose results - allows timely intervention for low glucose readings to avert serious hypoglycemic events

Question 34

When should SMBG be done?

Answer 34

- frequency of testing depends on many factors - fasting AM - before and after meals - before, during and after exercise - before bedtime - periodically 2-3 AM (Somogyi?)

Question 35

How often should SMBG be done in type 1 and type 2 DM?

Answer 35

- type 1 DM: at least 3x daily - type 2 DM: depends on degree of control and what meds the person is taking - should be done fasting AM, before and after meals, before, during and after exercise, and before bedtime

Question 36

Helpful ways to get good drop of blood from fingertip?

Answer 36

- rinse fingers with warm water - shaking hand below the waist - squeezing or milking fingertip

Question 37

Sources of error in SMBG?

Answer 37

- operator error: failure to calibrate the meter correctly, dirty meters, inadequate hand washing, improper storage of test strips - with decreasing blood sugars there is less accuracy - use of multiple sites (fingertips and forearms)

Question 38

levels of blood glucose in forearm and fingerstick?

Answer 38

- initially in first 120 minutes: fingerstick will have higher glucose levels - 120-210 minutes glucose levels higher from forearm stick

Question 39

What is continuous glucose monitoring?

Answer 39

- real-time monitoring - can be coupled with insulin pump - measures interstitial fluid by: needle sensor inserted subq or whole device implanted subq - expensive - not as accurate as fingerstick

Question 40

Data on CGM?

Answer 40

- group that had access to continuous display had less time with hypoglycemia and hyperglycemia, more time at target glucose range and less nocturnal hypoglycemia, although there wasn't a difference in A1C levels - another study compared SMBG and CGMS in poorly controlled insulin tx pts, improvement in A1C was same in both groups after 12 weeks, but those who used CGMS had less hypoglycemia