INTRODUCTION TO INTERPRETING LABORATORY DATA

Sensitivity – the ability of the test to identify positive results in patients who have the disease (true positive rate)

rule out condition

Specificity – the ability of the test to identify negative results in people without the disease (true negative rate)

rule in condition

List the chem 10 name

1. Na

2. K

3. CL

4. CO2

5. BUN

6. SCr

7. Glu

8. Ca

9. Mg

10. PO4

List the chem 10 values

1. 136-145 mEq/L

2. 3.5-5 mEq/L

3. 96-106 mEq/L

4. 24-30 mEq/L

5. 8-20 mg/dL

6. 0.7-1.5 mg/dL

7. 70-110 mg/dL

8. 8.5-10.8 mg/dL

9. 1.5-2.2 mEq/L

10. 2.6-4.5 mg/dL   

what molecules are found in intracellular fluid (ICF)

PO4, K

the plasma and the interstitial fluid makes up the

extracellular fluid (ECF)

what is found in interstitial fluid

Na, Cl, CO2

what is found in plasma (intervascular fluid)

Na, Cl, CO2

range of Sodium Na+

Primary extracellular cation

Regulates serum osmolality

Maintains electric potential for neuromuscular function

Excreted primarily by the kidneys

136-145 mEq/L

Hypernatremia 

1. Water loss greater than sodium loss
   Causes: profuse sweating and diarrhea
   Signs/Symptoms: thirst

2. Water loss without sodium loss
   -Causes: fever, burns, diabetes insipidus
   -Signs/Symptoms: thirst, confusion, weakness

3. Increase in total body sodium - increase ECF
   -Causes: Cushing's, hypertonic saline
   -Signs/Symptoms: thirst, confusion, weakness, increased urine sodium

>145 mEq/L

Hyponatremia

1. Solutes shift water from ICF to ECF

• Cause: hyperglycemia

• Signs/Symptoms: thirst, dry mucus membranes, diminished urine output

2. Extracellular volume depletion

• Causes: hemorrhage, diarrhea, vomiting, kidney damage, burns

• Signs/Symptoms: confusion, seizures, dehydration

3. Accumulation of water is greater than sodium dilution

• Causes: heart failure, cirrhosis

• Signs/Symptoms: confusion, seizures, edema

<136 mEq/L

range of Potassium K+

Primary intracellular cation

 Regulates muscle and nerve excitability

 Maintains acid/base balance

 Regulated by insulin, glucose, aldosterone, acid/base

balance, renal function, GI and skin losses

3.5-5.0 mEq/L

Hyperkalemia

 Can start to see symptoms at 5.5 mEq/L

 Causes: renal disease, diabetes, Addison’s disease,

medications

 Signs/Symptoms: diarrhea, muscle weakness,

**arrhythmia/EKG changes

>5.0 mEq/L

Hypokalemia

• Causes: vomiting, GI losses, Cushing’s disease,

medications

• Signs/Symptoms: constipation, muscle weakness, confusion, EKG changes

<3.5 mEq/L

range of Chloride Cl- 

• Primary extracellular anion

   Maintains resting membrane potential

   Maintains acid/base balance

   Regulated by the kidneys

   Increased Cl-:

   Metabolic or respiratory ____

   Decreased Cl-:

   Metabolic or respiratory ____

96-106 mEq/L, acidosis, alkalosis

range of Carbon Dioxide

24-30 mEq/L

CO2

• Integral component of carbonic acid/bicarbonate buffer system (acid bae balance)

• Acts as an acid

• Excreted by the lungs

• Increased CO2:

  • Causes: metabolic alkalosis (increased HCO3-), respiratory acidosis, hypernatremia

• Decreased CO2:

  • Causes: metabolic acidosis (↓ HCO3-), respiratory alkalosis, hyponatremia, GI loss, nasogastric suction, vomiting

24-30 mEq/L

Blood Urea Nitrogen 

BUN: Concentration of urea nitrogen in the serum and end product of protein metabolism

• Produced in the liver, filtered by the kidneys

• Increased BUN:

  • Acute/chronic renal failure

  • Dehydration

  • GI bleeds

  • High protein diet

• Decreased BUN:

  • Liver disease

8-20 mg/dL

Serum Creatinine (SCr) range

• The product of muscle breakdown

• Filtered and secreted but not reabsorbed

• Limitation of SCr as a predictor of kidney function:

  • Age

  • Increased SCr:

  • Medications

  • Renal disease

  • Decreased SCr:

  • Low muscle mass

0.7-1.5 mg/dL

Glucose range

• Energy source for cellular function

• Obtained from carbohydrates

• Stored in the liver and skeletal muscle as glycogen, stored in adipose tissues as fats and triglycerides

• Regulated by glucagon, insulin, cortisol, epinephrine, and other hormones

70-110 mg/dL

Hyperglycemia 

• Causes: food, diabetes, post-MI, infection, medications

• Signs/Symptoms: polyphagia, polyuria, polydipsia

>126 mg/dL

think “___!” for signs and symptoms of hyperglycemia 

poly

Hypoglycemia 

• Causes: exercise, poisoning

• Signs/Symptoms: palpitations, weakness, sweating, irritability, headache

<70 mg/dL

Calcium Ca2+ range

• Most abundant mineral in the body, found primarily in the bones

• 50% of calcium is protein bound

  • Low albumin → correct calcium level

• Role - muscle contraction, blood coagulation, nerve impulse, bone and tooth metabolism

• Regulated by vitamin D, serum phosphate, parathyroid hormone, and calcitonin

8.5-10.8 mg/dL

Hypercalcemia

• Causes: bone neoplasms, ATN, antacids, chronic diuretics

• Signs/Symptoms: muscle weakness, anorexia, GI disturbances, EKG

>10.8 mg/dL 

Hypocalcemia

• Causes: hypoparathyroid, Vitamin D deficiency, alcoholism, drugs

• Signs/Symptoms: numbness or tingling of the fingertips and around the mouth, fatigue, tetany, coma

<8.5 mg/dL

Magnesium Mg2+

• Second most abundant intracellular cation

• 50% in bone, remainder is exchanged between intracellular and extracellular space

• Maintains neuromuscular and enzymatic functions

• Co-factor for the movement of Na+, K+, and Ca2+ in and out of cells

• Excreted by the kidneys

1.5-2.2 mEq/L

Hypermagnesemia 

• Causes: renal failure, hyperparathyroid, lithium, magnesium antacids

• Signs/Symptoms: muscle weakness, n/v, confusion, respiratory depression, arrhythmia

>2.7 mEq/L

Hypomagnesemia

• Causes: diarrhea, thyroid, diuretics, alcohol, hypokalemia, hypophosphatemia

• Signs/Symptoms: muscle tremors, ocular nystagmus, altered mental status, arrhythmia, seizures

< 1.5 mEq/L

decrease in Mg also leads to decrease in

K+ and Phosphorous

Phosphorus range PO43-

• Primary intracellular anion

• Found in bone

• Role – energy metabolism, bone integrity, release of oxygen from hemoglobin

• Regulated by equilibrium of calcium

2.6-4.5 mg/dL

Hyperphosphatemia

• Causes: renal failure, bone disease, medications

• Signs/Symptoms: calcium deposits in soft tissue, bone pain

>4.5 mg/dL

Hypophosphatemia

• Causes: acute ETOH intoxication, malabsorption, starvation, aluminum antacids, steroids, diuretics, anticonvulsants, DKA

• Signs/Symptoms: muscle weakness, bone pain, rhabdomyolysis (muscle tissue breakdown leads to release of harmful substances), seizures, coma

<2.6 mg/dL 

HPI: Jeff is a 50 y/o male with a PMH significant for BPH, DM,

HTN, and hyperlipidemia who presents to the PCP office

complaining of dizziness, fatigue, headache, muscle spasm,

and tingling around the mouth.

TINGLING AROUND MOUTH* usually indicates ___ to be abnormal

calcium