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What are the monosaccharides and disaccharides w/ components?
- Glucose, fructose, galactose
- sucrose (glucose + fructose)
- lactose (glucose + galactose)
- maltose (glucose + glucose)
- *NOTE - absorbed as monos
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BASICALLY describe the major metabolic pathways (glycolysis, tricarboxylic acid cycle, glycogenesis, pentose phosphase/HMP shunt, glycogenolysis, gluconeogenesis)
- glycolysis: anaerobic, glucose -> pyruvate <-> lactate
- TCA: aerobic, glucose -> pyruvate + CO2 + H2O + ATP
- glycogenesis: glucose -> glycogen
- pentose phosphase/HMP shunt: glucose -> ribose + CO2 + NADPH
- glycogenolysis: glycogen -> glucose
- gluconeogenesis: noncarbohydrates (AA, lipids) -> glucose
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Insulin - synthesis/production, effect, testing
- Secreted by pancreated beta cells in response to increased blood glucose
- proinsulin -> insulin + C-peptide
- facilitates uptake of glucose into cells
- inc glyogenesis, glycolysis, and lipogenesis
- inhib glycogenolysis
- only hormone to lower blood glucose
- Testing primarily concerned w/ hypoglycemia
- Testing interpretation complicated
- C-peptide testing may be a better substitute
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What is C-peptide and why might it be tested?
- proinsuling -> insulin + C-Peptide
- Better substitute for insulin testing
- evaluating insulin-induced hypoglycemia
- endogenous insulin: elevated C-peptide (normal synth)
- exogenous insulin: normal/low C-peptide (eg artificial intake)
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Glucagon - synthesis/production, effect, testing
- Secreted by pacreatic alpha cells in response to low blood glucose
- stimulates glycogenolysis and gluconeogenesis in liver
- enhances ketogenesis
- raises blood glucose
- rarely measured
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How do cortisol, epinephrine, and growth hormone interact with blood glucose?
All RAISE blood glucose
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What is the problem with peroxidase steps in testing?
Interference with bilirubin, hgb, and vitamin C
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What are the intervals for glucose. What is a challenge of processing?
- Ref: 70-100mg/dL (fasting)
- Hypo (crit): <50mg/dL, <30 life threatening
- Hyper (crit): >500mg/dL
- Levels decrease 5-7%/hr in uncentrifuged blood (higher w/ high WBC)
- Oxalate tubes not effective for 1-2 hours
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3 causes of hypoglycemia
- Reactive: overshoot following a meal
- Decreased production: severe hepatic dysfunction, Addison's disease
- Increased uptake/utilization: over-administration of insulin (dec C-peptide), insulin-producing tumors (inc C-peptide)
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BASIC info for DM1, DM2, and GDM
- DM1: insulin deficiency is primary issue (autoimmune against beta cells)
- requires insulin replacement
- 5-10% of all cases
- DM2: insulin resistance is primary issue
- not as
- 90% of all cases
- GDM: insulin resistance is primary issue
- onset/diagnosis during pregnancy
- *macrosomia and hypoglycemia in baby (response to hyperglycemic mother)
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Acute vs chronic complications of DM
- Acute: glucose deficit within cells (glucose can't get in)
- hyperosmolar hyperglycemic state (HHS)
- chronic: glucose excess over time causes damag
- acute leads to diabetic ketoacidosis (lipolysis, acetoacetate formation)
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What are the ketone bodies? Describe the testing
- Acetoacetate, Acetone, beta-hydroxybutyrate
- Acetest/ketostix: urine/serum dipsticks
- BHB enzymatic: quant and spp, automated
- AcOAc and BHB normally low, ~equal
- Excess NADH from lipolysis pushes >70% to BHB
- *NOTE - BHB dec and AcOAc inc during recovery
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How do you diagnose DM?
- ANY ONE OF THE FOLLOWING...
- Hgb A1C ≥6.5% (not using POCT)
- Fasting plasma glucose ≥126mg/dL
- 2hr plasma glucose ≥200mg/dL during oral glucose tolerance test
- Random plasma glucose ≥200mg/dL WITH symptoms of hyperglycemia
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Describe the oral glucose tolerance test (GTT) and its interpretation
- For fasting, ambulatory, non-preggos
- Given 75gm glucose
- Diabetes: fasting sample ≥126mg/dL or 2hr sample ≥200gm/dL
- Impaired glucose tolereance: 2 hr 140-199mg/dL
- Impaired fasting glucose: 101-125mg/dL ("prediabetes")
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Describe the process to diagnose GDM
- 50g 1hr GTT (non-fasting)
- if ≥140mg/dl then...100g 3hr fasting GGT
- exceeding any 2/4 cutoffs over a 3 hour period (including fasting draw) signifies GDM
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What is Hgb A1 w/ variants. Compare/contrast the 3 testing methods
- Hgb A1: glycated Hgb (A1a1, A1a2, A1b, A1c)
- A1c has an attached glucose (relevant to blood glucose levels over past 120 days)
- Normally 4-5% of HgbA
- 80% of all Hgbs
- Ion exchange chrom: separates based on charge change when glucose binds
- potential interference w/ some alt Hgbs
- Immunoassay: Ab against the glycopeptide Ag
- may require manual dilution
- potential interference w/ some alt Hgbs
- Affinity chrom: only binds glycated Hgb
- binds all glycated Hgb, calculation must reduce value to accurate A1C value
- Typical POC method
- *note - decreased RBC life underestimates the true value
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What is fructosamine?
- Generic name for glycated plasma proteins (ketoamine adducts)
- These can be measured, and indicated a more narrow timeframe than A1c
- Useful for hemoglobinopathies, anemia, and GDM
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What is the purpose of the microalbumin test?
- Demonstrates minimal (initial) glomerular damage from diabetes
- *note- small amounts of albumin in urine, not detected by dipstick
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How is iron transported and stored? (3 subs + general info)
- FREE IRON IS TOXIC
- Transferrin: binds 2x Fe3+ ions in serum
- in excess, normally 20-50% saturation
- special receptor for tissue uptake
- Ferratin: binds up to 4500 Fe3+ in most cells
- Readily mobilized if needed
- Hemosiderin: insoluble complex derived from ferritin
- releases iron less readily than ferratin
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Serum iron measurement test basics
- Fe3+ is released from binding proteins (not heme/Hgb) by acidification
- Reducing agent (vit c?) = Fe3+ -> Fe2+
- binds to a dye and is measured
- tests should include iron-binding capacity
- iron shows diurnal variation (highest in AM)
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transferrin measurement test basics
- Direct: immunoassay against transferrin
- TIBC: total iron binding capacity
- add excess Fe3+ to sample (equilibrate)
- complex non-bound iron and separate it
- measure Trf-bound iron
- UIBC: unsaturated iron binding capacity
- add excess Fe3+ to sample (equilibrate)
- measure unbound iron only*NOTE - tferrin sat = Fe/TIBC x 100%
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Ferritin test basics
- Measured directly by immunoassay (sandwich)
- ferritin is proportional to stored iron levels
- *NOTE - acute phase reactant! Inflammation will artificial inflate the result.
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3 stages of iron deficiency anemia
- Iron depletion: depletion of stores (ferritin decrease)
- normal serum iron and TIBC
- No anemia or abnormal RBCs
- Iron-deficient erythropoiesis: decreased iron for erythropoeisis (stores depleted)
- decreased ferratin, serum iron, transferrin saturation
- increased TIBC, transferrin
- No anemia
- slightly microcytic RBCs, increased RDW
- Iron deficiency anemia: Decrease in ferritin, iron, transferrin saturation
- Increase in TIBC, transferrin
- decrease in Hgb, MCV, MCH, MCHC
- increased RDW
- microcytic, hypochromic anemia
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What are porphyrias? How might they manifest?
- Rare disorders of partial enzyme deficiency for creation of porphyrin rings (heme, cytochromes)
- *NOTE - could not be full deficiency or life could not exist (cytochromes)
- buildup of ALA since heme does not inhibit -> symptoms
- Acute neurologic presentations
- Chronic photosensitivity
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Copper - function, transport, deficiency symptoms, excess symptoms
- function: enzyme cofactor
- transport: bound to ceruloplasmin (α2 globulin)
- deficiency: microcytic, hypochromic anemia
- neutropenia
- excess: Wilson's disease (copper deposition in tissues, esp liver/brain)
- decreased ceruloplasmin and serum Cu, with elevated urine Cu
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compare/contrast Fat soluble vitamins vs water soluble vitamins
- Fat soluble: A, D, E, K
- readily stored in body, deficiency develops slowly
- Water soluble: Thiamine (B1), Niacin (B3), Pyridoxine (B6), Cobalamin (B12), Ascorbic acid (C)
- Not stored (except B12), require continuous intake
- Toxicity uncommon (except B6)
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Vitamin B12 - structure, absorption/storage, testing, deficiency symptoms
- AKA Cobalamin
- structure: ring with Co+ (not Fe) coordination atom
- abs/stor: absorption requires low pH to dissociate B12 from food and intrinsic factor to absorb
- stored in liver (5 year supply)
- testing: immunoassay OR intrinsic factor binding assay
- def: megaloblastic anemia, irreversible neuropathy
- treat w/ intramuscular injections if necessary
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Folate: what is the problem?
- Serum folate can be skewed by a single salad before the test
- Not representative of that actual picture
- RBC better reflects body stores
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Why does macronutrition revolve around protein?
- We cannot synthesize essential AA
- We do not recycle nitrogen well
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What is nitrogen balance and what is the best marker?
- Reltionship of nitrogen intake vs excretion
- Prealbumin is the most common marker due to it's fast half life (2 days)
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Describe a basic electrophoresis setup (charges, pH, application, etc)
- Cathode: negative
- Anode: positive
- gel pH 8.6 (makes all proteins neg charge)
- application of sample at cathode (moves toward anode)
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What is electroendosmosis?
- A net solvent flow toward the cathode that occurs during electrophoresis
- Uncharged/low charge proteins will migrate toward cathode w/ the solvent (charged proteins migrate toward anode)
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How is isoelectric focusing different from other electrophoretic methods?
- Isoelectric focsing has a pH gradient
- Proteins STOP migrating when they reach their isoelectric point (pI)
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What is hypergammaglobulinemia? Categories w/ examples
- Polyclonal: increase in multiple Igs
- Monoclonal: single Ig (paraprotein or M-protein)
- Multiple myeloma (plasma cell malignancy)
- Lymphoid tumors
- Waldenstrom macroglobulinemia (IgM, bence-joyce)
- Heavy chain disease
- Serum free light chains (inc levels or abn ratio)
- *NOTE - malig can also be non-secretory (no Ig production)
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What are cryoglobulins and why might they cause testing trouble? How can you test for them?
- Igs that reversibly ppt at >37C
- They can ppt in analyzers causing performance issues
- Test via collect and cfuge @37, incubate @4 for several days, reinc @37 and see what redissolves
- NOTE - related to monoclonal gamm.
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What are the three REVERSE acute phase reactants?
Albumin, Pre-albumin, and transferrin
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IEP vs IFE
- Immunoelectrophoresis: very difficult/confusing
- antisera in adjacent trophs with sample innoc between
- Looking for thickening/arc at zone of equivalent (ppt sample)
- Immunofixation: G, A, M, κ, λ
- 6 lanes of sample are electrophoresed
- Addition of antisera to 5 lanes (#6 is ref)
- Look for abnormalities (heavy + light?)
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