GLUCOSE AND DIABETES Flashcards
Define hypoglycemia
- abnormally low blood glucose
ie. diabetic patients being treated with insulin
Define and describe hyperglycemia
- abnormally high blood glucose
- due to hormonal imbalance
- defects in insulin secretion or action (insulin is supposed to decrease glucose levels)
Describe the OGTT procedure
- evaluates glucose clearance
PROCEDURE:
- patient ingests min 150g carbs/ day for three days
- fasting 10 to 16 hours prior to test while ambulatory
- since glucose is diurnal, test is done in the morning
- fasting glucose blood specimen is drawn
- a second sample is drawn after patient ingests 75g glucose within 5 minutes
Type I vs Type II diabetes mellitus
Type I:
- insulin-dependent AND immune-mediated
- beta cells in pancreas are destroyed by autoantibodies
- usually develops in children/ teens
- prone to ketosis
Type II (90%):
- insulin-resistance; normal levels of insulin but defective action
- beta cells produces more insulin to compensate
- more common in adults
Ref: fasting glucose serum/plasma
3.3 - 6.0 mmol/L
Ref: CRITICAL for fasting and random glucose
<2.6 OR >24.9 mmol/L
Ref: random glucose serum/ plasma
3.3 - 11.1 mmol/L
Ref: fasting OGTT serum/plasma
3.3 - 6.0 mmol/L
Ref: 2h OGTT serum/ plasma
≤ 7.8 mmol/L
Ref: CSF glucose
2.2 - 4.4 mmol/L
Ref: HbA1c
4.3 - 6.1%
Ref: lactic acid
0.5 - 2.2 mmol/L
CRITICAL: >4.0 mmol/L
Hypoglycemia in diabetic patients can be a result of what 2 things ?
- defective glucagon secretion
- glucagon is supposed to increase glucose levels - decreased epinephrine response to hypoglycemia
How is hypoglycemia differentiated in people without diabetes ?
FASTING hypoglycemia:
- starvation
- drugs ie. ethanol, salicylates
POSTPRANDIAL hypoglycemia:
- drugs ie. insulin
- antibodies to insulin (receptors)
- inborn errors of metabolism
What is the whipple triad ?
- used to diagnose hypoglycemia:
1. trembling, sweating, nausea, rapid pulse, lightheaded symptoms
2. low blood glucose
3. symptoms are relieved by glucose administration
__ is a group of diseases associated with hyperglycemia
DIABETES MELLITUS is a group of diseases associated with hyperglycemia
Describe gestational diabetes mellitus
- a temporary condition onset of pregnancy
- associated with increased morbidity
- mother and child are at an increased risk of developing diabetes
- fetal macrosomia
Define prediabetes
- individuals at high risk of developing type II diabetes
- abnormal fasting glucose, OGTT, or hA1c but do not meet criteria of diagnosis yet
- can revert to normal glycemia but at risk for cardiovascular disease
How is diabetes diagnosed ?
- same testing used to screen for disease:
a). fasting blood glucose > 7.0 mmol/L
b). HbA1c ≥ 6.5%
c). 2hr OGTT ≥ 11.1 mmol/L
Why must the patient be ambulatory when performing the OGTT ?
Inactivity decreases glucose tolerance
T or F: the OGTT has good reproducibility
FALSE; the OGTT has POOR REPRODUCIBILITY
- variables such as fasting, age, activity, illness, oral contraceptives, corticoid steroids, weight, smoking, caffeine, stress, and posture all affect the OGTT
When is prediabetes diagnosed after an OGTT ?
a). fasting glucose (<6.1 mmol/L) and 2h OGTT glucose (7.8 mmol/L) are both within range
b). fasting glucose is higher (6.1 - 6.9 mmol/L) but 2h OGTT glucose is within range (7.8 mmol/L)
c). fasting glucose (6.1 - 6.9 mmol/L) and 2h OGTT glucose are both higher (7.8 - 11.0 mmol/L)
RECALL: diabetes diagnosis requires fasting glucose ≥ 7.0 mmol/L and 2hr OGTT glucose ≥ 11.1 mmol/L
Glucose samples collected in the morning have a higher glucose concentration because of __
Glucose samples collected in the morning have a higher glucose concentration because of DIURNAL VARIATION
Specimen type for blood glucose testing
Serum* or plasma:
- should immediately be spun down to prevent glycolysis = stable for 8 hours at RT
- NaF anticoagulants can temporarily inhibit glycolysis (bacterial contamination decreases glucose)
24-hour urine:
- collected with 5 mL acetic acid to inhibit bacterial contamination
Urine:
- referigerated
CSF:
- STAT; bacteria may be present
What is the reference method for blood glucose testing ? Why ?
Glucose Hexokinase method; suitable for blood, urine and CSF !
Interferences for Glucose Hexokinase method
severe HIL = falsely decreased blood glucose levels
Specimen types for Glucose oxidase method
Blood and CSF ONLY
- NOT URINE
Interferences of Glucose Oxidase method
- Hemolysis (hemoglobin)
- Icterus (bilirubin)
- Ascorbic acid/ vitamin C
- Uric acid
ALL INHIBIT REACTION
POCT devices typically use which 2 glucose methods for quantitative results ?
- Glucose oxidase
- Glucose dehydrogenase
Specimen types for POCT devices
Whole blood; has lower glucose levels than plasma/ serum
Interferences for POCT devices
- incorrect specimen application
- temperature
- humidity
Why is CSF glucose tested ?
Differentiates between viral vs bacterial meningitis:
Bacterial/ carcinomatous = LOW glucose
Viral = normal glucose
T or F: A positive urine test is NOT diagnostic for diabetes mellitus
TRUE; a urine test is ONLY used as a SCREENING tool to MONITOR diabetes
Is glucose normally found in urine ?
NO; GLUCOSE IS NOT NORMALLY FOUND IN URINE
Define glycosuria
- glucose in urine
- associated with uncontrolled diabetes mellitus, advanced renal disease, and pregnancy
- glucose exceeds renal threshold >11.0 mmol/L
What test is used for management of diabetes ?
HbA1C:
- determined using HPLC or immunoassays
- used to diagnose or monitor diabetes mellitus
- hemoglobin A becomes irreversibly bound to glucose = glycated
- proportional (%) to average glucose over an RBC’s lifespan (120 days)
- measured every 3-4 months EXCEPT for pregnant women
What is the urine albumin: creatinine ratio (ACR) used for ?
- used to monitor kidney function of people with diabetes AND screen for early kidney damage
- ACR > 3 mg/mmol is clinically significant
Why is urine albumin:creatinine ratio (ACR) used instead of a 24-hour urine collection ?
- 24-hour urine specimens fluctuate depending on hydration status; ACR accounts for variation
- first-morning void specimens are ideal for ACR
What are ketones ?
- fatty acids are metabolized during prolonged starvation = excess acetyl-coA
- also seen in impaired carbohydrate metabolism ie. diabetes mellitus
If metabolic acidosis is suspected, a quantitative test for __ is ordered.
If metabolic acidosis is suspected, a quantitative test for β-HYDROXYBUTYRATE is ordered
Specimen type and stability for β-hydroxybutyrate
Unspun whole blood (lithium heparin or EDTA)
- stable for 2 hours at RT or 48 hours refrigerated
How is β-hydroxybutyrate detected ?
- Colorimetric method
- GC-MS
T or F: ketones are NOT normally found in urine
TRUE; KETONES ARE NOT NORMALLY FOUND IN URINE
Fatty acid metabolism in the liver produce ketone bodies. Identify the 3 types. Which is the ONLY one detected by urine reagent strips ?
- Acetoacetic acid* IS THE ONLY ONE DETECTED BY URINE REAGENT STRIPS
- β-hydroxybutyric acid
- Acetone
Describe the principle behind lactic acidosis
- lactic acid is mainly produced in muscle, the medulla of the kidney, and RBCs
- oxygen deprivation leads to blockage of aerobic oxidation of glucose; pyruvate is reduced to lactate, instead of acetyl CoA
- lactate: pyruvate ratio increases and blood lactate levels rise
Differentiate the 2 types of lactic acidosis
Type A*:
- respiratory; severe tissue hypoxia (more common)
ie. anemia, shock, pulmonary insufficiency, cardiac failure
Type B:
- metabolic
ie. diabetes mellitus, liver disease, drugs (ethanol, methanol, salicylates), inborn errors of metabolism
Ref: lactic acid
0.5 - 2.2 mmol/L
CRITICAL: >4.0 mmol/L
Specimen type for lactic acid testing
- potassium oxalate OR heparin ON ICE
- DO NOT USE TOURNIQUET
- specimen is immediately cooled and spun to prevent glycolysis (false increase)
What method is used to test for lactic acid ?
Lactate dehydrogenase; oxidizes lactate back to pyruvate = increase in absorption
