Lab Med - Endo Pancreas Flashcards
What is the purpose of the urine albumin-to-creatine ration (UACR)
Detect early kidney disease in those with diabetes or other risk factors such as HTN
What factors affect the results of UACR
- Blood in the urine, UTI, vigorous exercise, other acute illness may cause false positive (not related to kidney disease)
- Infection, fever, CHF, marked hyperglycemia, and marked HTN can all increase albumin levels
- Repeat testing after conditions have resolved
What is normal UACR range
0-30 mg/g albumin excretion/day
What is abnormal UACR range
UACR > 30 mg/g
*marker for CKD
Explain the results of UACR
- Moderately increased albumin levels in initial and repeat tests indicate person likely to have early kidney disease
- Very high levels indicate kidney disease is present in a more severe form
- Undetectable levels are an indication kidney function is normal
Purpose of A1C
- Screen or dx diabetes or prediabetes in an adult
- Monitor response to therapy
What does A1C test?
- Percent of glycated hemoglobin in the blood
- Glycated hemoglobin is hemoglobin to which glucose is bound. It is increased with poorly controlled DM. Glucose stays attached to hemoglobin for the life of the red blood cell – level of glycosylated hb reflects average blood glucose level over the past 3 months
When to order A1C
- Screening adults at risk for DM or preDM
- Pt presents with sx of hyperglycemia
- All adults >45 yo
- Monitor response to therapy
A1C range for
- non-DM
- pre-DM
- DM
- Non-diabetic <5.7%
- Prediabetes 5.7-6.4%
- Diabetes >6.5%
What factors affect A1C results?
- Hemoglobinopathies
- Abnl hemoglobin turnover rate (sickle cell, hemolytic anemia)
- Conditions associated with increased cell turnover (pregnancy)
- Hemodialysis
- Recent blood loss or transfusion
- Erythropoietin therapy
What is purpose of oral glucose test?
- To screen for or diagnose DM or preDM
- Screen for gestational DM during pregnancy
When order an OGTT
- 24-28 weeks gestation
- If screening for DM or pre-DM and fasting plasma glucose and A1c are not available or produce equivocal results
Patient test prep for OGTT
- Pt should be active and eat a regular diet that includes at least 150 g of CHO daily for 3 days prior to the test
- Fast 8-14 hours prior to test
- Discontinue any nonessential meds that affect glucose metabolism min 3 days before test
Describe the 2-step 2-hour OGTT for gestational diabetes
- First, perform the glucose challenge test as a screen
• 50 g glucose drink, measure blood glucose in 1 hour - If abnl, then perform 3 hour oral glucose tolerance test
• Msr fasting glucose then drink 100 g glucose
• Measure glucose at 1 hr, 2 hr, 3 hr
• If 2 or more of the measurements (fasting, 1, 2, 3 hr) are abnl, dx of gestational DM
What is patient prep for c-peptide test
14-16 hour fast to get basal level
What does c-peptide test?
- When insulin’s precursor molecule, proinsulin, is cleaved to make insulin, C-peptide is formed as a byproduct
- Insulin and c-peptide as secreted in equimolar amounts and released into circulation via the portal vein
Explain the c-peptide results
- Elevated levels of c-protein indicate insulin resistance
- Levels in the normal range in the face of hyperglycemia indicate a dysfunctional insulin release that cannot keep blood glucose in physiologic range
- Expect to see levels at the low end of normal or less than normal in early DMI
Normal osmolality range for people < 61 yo
275 – 295 mOsm/kg
What lab findings might be found in a person who is dehydrated and has hyperglycemia?
high serum osmolality
Three ketone bodies
- acetone
- acetoacetate
- beta-hydroxybutyrate
Why are ketones produced?
- Ketones are produced by the body as an alternative to glucose
- When the body has too little insulin, cells cannot take in enough glucose from the blood. To compensate, the body will break down fat to produce ketones (ketosis)
When should ketones be ordered or patient advised to check for ketones
- Screen for, detect, and monitor DKA
• Beta-hydroxybutyrate is the predominant ketone in severe DKA
• Pts with DM are at higher risk for DKA when pregnant or sick - In pt without DM to detect ketoacidosis dt a non-DM cause such as excessive ingestion of alcohol
- Order when glucose levels remain above 250-300 mg/dL (can be done at home with a urine strip)
What is creatinine and why is it a good surrogate marker for estimating GFR
- Creatinine is the dehydrate product of creatine (once formed, cannot be turned back into creatine).
- Creatinine is formed at a relatively constant rate in muscle, it is freely filtered through the glomerulus, not appreciably reabsorbed or secreted by the renal tubules
- Serum concentration of creatinine represents a balance between production and glomerular filtration rate. Assuming the production rate is constant, the clearance of creatinine is a good surrogate for GFR which can’t be directly measured
What must be monitored in pts taking metformin long-term
B12
What is the usual reference range for serum potassium
3.5-5.1 mEq/L
What meds increase serum potassium
ACE inhibitors
ARBs
What meds decrease serum potassium
diuretics
What is the impact of acidosis on serum K levels and total body K
- In acidosis, the H ion moves intracellularly, displacing potassium, which moves into the blood. Once in the blood, the kidneys excrete the potassium.
- If long term acidosis, can lose a sig portion of the body’s potassium
- If a person is in DKA and has normal serum potassium, a major potassium loss has occurred
What are the sources of ALT
Liver and kidney
What are the sources of AST
- Liver and heart mostly
- Also muscle, RBC, pancreas, kidney, brain
Why are AST and ALT monitored in people with DM?
due to risk of NASH and NAFLD
What is normal serum glucose range
70-99 mg/dL
What is a fasting glucose
no caloric intake in 8 hours
State the ranges for
- hypoglycemia
- normal bs
- hyperglycemia
- Hypoglycemic is <70 mg/dL
- Normal is 70-99 mg/dL
- Hyperglycemic is >99 mg/dL
What is the purpose of using fructosamine
- Evaluate DM control over a shorter time period (1-3 weeks) than A1C (8-12 weeks)
- Index of longer-term control than glucose levels, especially in pts with DM and abnormal hemoglobin
When should fructosamine be ordered
- When can’t order A1C
- When need shorter term assessment of glycemic control
