LMT YOUNG NOTES

Bilirubin, mg/dL to umol/L

17

Creatinine, mg/dL to umol/L

88

Sodium/potassium, chloride, mEq/L to mmol/L

1

TP/albumin/globulin, g/dL to g/L

10

lg conversion factor from mg/dL to mg/L

10

lg conversion factor from mg/dL to g/L

0

Thyroxine ug/dL to nmol/L

12

BUN conversion factor from mg/dL to mmol/L

0

BUN to urea

2

Urea to BUN

0

Normal BUN:Creatinine ratio

10-20:1

Creatinine

Indirect method used to assess the glomerular filtration capabilities of the kidneys

β2 microglobulin

Appears in the urine when reabsorption is incomplete because of proximal tubular damage, as in acute kidney injury

Assay for urea that is inexpensive but lacks specificity

Colorimetric, diacetyl

Assay for urea that measures ammonia formation

Enzymatic

Assay for uric acid, problems with turbidity

Colorimetric

Assay for uric acid that needs special instrumentation and optical cells

Enzymatic: UV

Chronic renal failure

A progressive and irreversible loss of renal function, results from several disease entities.

Heparin

Least interference with analysis

Lithium heparin

Heparin for most chemistry tests

Glucose is metabolized at room temperature

7 mg/dL/hour

Glucose is metabolized at 4℃

2 mg/dL/hour

Hypoglycemia

Blood glucose level less than 50 mg/dL

OGTT

Patient should be ambulatory; fasting of 8 to 14 hours, unrestricted diet of 150 grams CHO/day for 3 days prior to testing

Glycosylated hemoglobin

Performed routinely to monitor glucose control

Gestational diabetes patients develop diabetes

Within 5 to 10 years

Sodium concentration in patient with DM

Decreased due to polyuria

Cholesterol

CV≤3%

Triglycerides

CV≤5%

LDLs, HDLc

CV≤4%

Major structural protein in HDL

Apo A1

Major structural protein in VLDL and LDL

Apo B100

Structural protein in chylomicrons

Apo B48

LDL cholesterol may be calculated from measurements of:

TC, TAG and HDL-c

Floating beta-lipoprotein

B-VLDL

Sinking pre-beta lipoprotein

Lp (a)

HDL cholesterol protective against heart disease

≥60 mg/dL

HDL cholesterol major risk for heart disease

<40 mg/dL

Serum cholesterol: moderate risk >170 mg/dL, high risk >185 mg/dL

2-19 years old

Serum cholesterol: moderate risk >200 mg/dL, high risk >220 mg/dL

20-29 years old

Serum cholesterol: moderate risk >220 mg/dL, high risk >240 mg/dL

30-39 years old

Serum cholesterol: moderate risk >240 mg/dL, high risk >260 mg/dL

40 and over

One-step, direct method for cholesterol

Liebermann-Burchardt (L-B) procedure

Current reference method for cholesterol

Abell-Kendall method

Chloride

Counterion of sodium

Routinely measured electrolytes

Sodium, potassium, chloride and bicarbonate

Largest contribution to the osmolality value of serum

Sodium, chloride and bicarbonate

Osmolality of plasma

Na + glucose (mg/dL) + BUN (mg/dL) or 1.86 Na + glucose + BUN + 9

Osmolal gap

Difference between the measured osmolality and the calculated osmolality; indirectly indicates the presence of osmotically active substances other than Na+, urea, or glucose, such as ethanol, methanol, ethylene glycol, lactate, or β-hydroxybutyrate

Anion gap

Na - (Cl + HCO3); NV 7 to 16 mmol/L

Anion gap exceeds 16 mmol/L

Indication of increased concentrations of the unmeasured anions (PO4 3-, SO4 2-, protein ions)

Increased anion gaps

Can also result from ketotic states, lactic acidosis, salicylate and methanol ingestion, uremia, or increased plasma proteins.

Decreased anion gaps

Less than 10 mmol/L; either an increase in unmeasured cations (Ca2+, Mg2+) or a decrease in the unmeasured anions.

Anion gap as quality control

The anion gap is also useful as a quality control measure for electrolyte results. If an increased anion gap is found for electrolytes in a healthy person, one or more of the test results may be erroneous, and the tests should be repeated.

Most common cause of hyperkalemia

Due to therapeutic K+ administration. The risk is greatest with IV K+ replacement.

Sodium (Na+)

The most abundant cation in the ECF, representing 90% of all extracellular cations, and largely determines the osmolality of the plasma.

Normal plasma osmolality

Approximately 295 mmol/L, with 270 mmol/L being the result of Na+ and associated anions.

Na+ reabsorption

Normally, 60% to 75% of filtered Na+ is reabsorbed in the PCT; electroneutrality is maintained by either Cl- reabsorption or hydrogen ion (H+) secretion.

Potassium (K+)

The major intracellular cation in the body involved in regulation of neuromuscular excitability, contraction of the heart, ICF volume, and H+ concentration.

Hyperkalemia

Decreased renal excretion.

Hypokalemia

Gastrointestinal loss.

Acute or chronic renal failure

GFR < 20 mL/min.

Vomiting

A cause of hypokalemia.

Diarrhea

A cause of hypokalemia.

Hypoaldosteronism

A cause of hypokalemia.

Addison's disease

A cause of hypokalemia.

Diuretics

A cause of hypokalemia.

Gastric suction

A cause of hypokalemia.

Intestinal tumor

A cause of hypokalemia.

Malabsorption

A cause of hypokalemia.

Cellular shift

Acidosis, muscle/cellular injury, chemotherapy.

Cancer therapy

Chemotherapy, radiation.

Renal loss

Diuretics - thiazides, mineralocorticoids.

Leukemia

A cause of renal loss.

Hemolysis

A cause of renal loss.

Nephritis

A cause of renal loss.

Renal tubular acidosis

A cause of renal loss.

Hyperaldosteronism

A cause of increased potassium intake.

Cushing's syndrome

A cause of increased potassium intake.

Hypomagnesemia

A cause of increased potassium intake.

Artifactual causes

Sample hemolysis, thrombocytosis, prolonged tourniquet use or excessive fist clenching.

Chloride (Cl)

The major extracellular anion involved in maintaining osmolality, blood volume, and electric neutrality.

Hyperchloremia

Caused by renal tubular acidosis, diabetes insipidus.

Hypochloremia

Caused by prolonged vomiting, aldosterone deficiency, metabolic alkalosis, salt-losing nephritis.

Bicarbonate

The second most abundant anion in the ECF, with HCO3- accounting for ≥90% of the total CO2 at physiologic pH.

Calcium (Ca2+)

Involved in blood coagulation, enzyme activity, excitability of skeletal and cardiac muscle, and maintenance of blood pressure.

Hypercalcemia

Caused by calcitonin, hypoparathyroidism, alkalosis, renal failure, vitamin D deficit.

Hypocalcemia

Caused by cancer, hyperthyroidism, iatrogenic causes, multiple myeloma, hyperparathyroidism.

Parathyroid hormone

Enhance resorption from bone, stimulate vitamin D synthesis, enhance renal tubular reabsorption.

Calcitonin

Stimulate calcium uptake by bone, decrease renal tubular reabsorption.

Vitamin D metabolites

Enhance intestinal absorption, enhance resorption from bone, increase renal tubular reabsorption.

Hyponatremia

A condition characterized by low sodium levels in the blood.

Hypernatremia

A condition characterized by high sodium levels in the blood.

Excess water loss

Causes include diabetes insipidus, renal tubular disorder, prolonged diarrhea, profuse sweating, and severe burns.

Increased sodium loss

Causes include hypoadrenalism, potassium deficiency, diuretic use, ketonuria, salt-losing nephropathy, prolonged vomiting or diarrhea, and severe burns.

Decreased water intake

Common in older persons, infants, and individuals with mental impairment.

Increased water retention

Causes include renal failure, nephrotic syndrome, hepatic cirrhosis, and congestive heart failure.

Increased intake or retention

Causes include hyperaldosteronism, sodium bicarbonate excess, and dialysis fluid excess.

Water imbalance

Causes include excess water intake, SIADH, and pseudohyponatremia.

Phosphorus

Inversely related to calcium; essential for insulin-mediated entry of glucose into cells.