Quiz 5: Electrolytes

Question 1

What is the major intracellular cation and major extracellular cation, respectively?

(a) Calcium, sodium
(b) Magnesium, calcium
(c) Potassium, sodium
(d) Sodium, potassium

Answer 1

(c) Potassium, sodium

Question 2

The main difference between a direct and indirect ISE measurement for electrolytes is:

(a) Direct ISEs use a reference electrode, whereas indirect ISEs do not
(b) Sample is diluted in the indirect method, not in the direct method
(c) The type of membrane that is used
(d) Whole blood samples can be measured with the direct method and not with the indirect method

Answer 2

(b) Sample is diluted in the indirect method, not in the direct method

Question 3

Which plasma electrolyte has the most narrow reference intervals and is MOST strictly regulated by the body?

(a) Calcium
(b) Magnesium
(c) Potassium
(d) Sodium

Answer 3

(c) Potassium

Question 4

A hemolyzed sample will NOT cause falsely increased levels for which electrolytes?

(a) Magnesium and potassium
(b) Phosphate and magnesium
(c) Potassium and phosphate
(d) Sodium and calcium

Answer 4

(d) Sodium and calcium

Question 5

The most common method for measuring sodium and potassium is:

(a) Atomic absorption spectrophotometry
(b) Enzymatic methods
(c) Flame emission spectrophotometry
(d) Ion selective electrode

Answer 5

(d) Ion selective electrode

Question 6

Which of the following values is a threshold critical value (alert or action level) for low plasma potassium and the physician needs to be notified?

(a) 2.5 mmol/L
(b) 3.0 mmol/L
(c) 3.5 mmol/L
(d) 4.0 mmol/L

Answer 6

(a) 2.5 mmol/L

Question 7

Which of the following values is a threshold critical value (alert or action level) for a high potassium and the physician needs to be notified?

(a) 4.5 mmol/L
(b) 5.0 mmol/L
(c) 5.5 mmol/L
(d) 6.3 mmol/L

Answer 7

(d) 6.3 mmol/L

Question 8

Which of the following values is the threshold critical value (alert or action level) for high plasma sodium and the physician needs to be notified?

(a) 145 mmol/L
(b) 150 mmol/L
(c) 155 mmol/L
(d) 161 mmol/L

Answer 8

(d) 161 mmol/L

Question 9

Which formula is most accurate in predicting plasma osmolality, an indirect measurement of particles in plasma?

(a) Na + 2(Cl) + BUN + Glucose
(b) 2(Na) + 2(Cl) + Glucose + Urea
(c) 2(Na) + (Glucose/18) + BUN(2.8)
(d) (Na + K) - (Cl + HCO3)

Answer 9

(c) 2(Na) + (Glucose/18) + BUN(2.8)

Question 10

The sample of choice for measuring blood osmolality is:

(a) Plasma
(b) Serum
(c) Whole Blood
(d) Serum or plasma may both be used

Answer 10

(b) Serum

Question 11

Which of the following are true about an indirect ion selective electrode test?

(a) Hyperlipemia, hyperglycemia, and proteinuria may cause falsely elevated sodium results
(b) Hyperlipemia, hyperglycemia, and proteinuria may cause falsely low sodium results
(c) No dilution is made
(d) All of the above is true

Answer 11

(b) Hyperlipemia, hyperglycemia, and proteinuria may cause falsely low sodium results

Question 12

Which of the following conditions will cause erroneous calcium results on a sample measured within one hour?

(a) Analysis of plasma collected in lithium heparin
(b) Analysis of plasma collected in EDTA
(c) Analysis of serum in a barrier gel tube
(d) Slight hemolysis in the plasma or serum

Answer 12

(b) Analysis of plasma collected in EDTA

Question 13

Given the following serum electrolyte data, determine the anion gap:
Na=132 mmol/L; K=4.0 mmol/L; Cl=90 mmol/L; HCO3-=22 mmol/L
(a) 12 mmol/L
(b) 24 mmol/L
(c) 27 mmol/L
(d) 64 mmol/L

Answer 13

(b) 24 mmol/L

Question 14

Which percentage of total serum calcium is nondiffusible protein bound?

(a) 10-30%
(b) 40-50%
(c) 51-60%
(d) 80-90%

Answer 14

(b) 40-50%

Question 15

The best method for ionized calcium involves the use of:

(a) Biuret reaction that removed protein prior to bind with arsenazo ions to cause change in voltage
(b) 8-hydroxyquinoline selective membrane that binds with Ca+2 to prevent other ions which may change potential
(c) Ion selective electrode that detects change in potential when Ca+2 binds reversibly to the membrane
(d) Valinomycin incorporated into a semipermeable membrane that allows for change in current

Answer 15

(c) Ion selective electrode that detects change in potential when Ca+2 binds reversibly to the membrane

Question 16

A patient with a myeloproliferative neoplasm has the following values: 
Hgb= 13 g/dL (130 g/L)
Hct= 38% (0.38 L/L)
WBC= 30 x 10^9/L
Platelets = 500,000 mcL
Serum Na+ = 140 mmol/L (140 mEq/L)
Serum K+= 7 mmol/L 
The serum K+ must be confirmed by: 
(a) Atomic absorption spectrometry
(b) Repeat testing of the original serum
(c) Testing freshly drawn serum
(d) Testing heparinized plasma

Answer 16

(d) Testing heparinized plasma

Question 17

A potassium level of 6.8 mmol/L (6.8 mEq/L) is obtained. Before reporting the results, the first step the medical laboratory scientist should take is to:

(a) Check the age of the patient
(b) Check the serum for hemolysis
(c) Do nothing, simply report out the result
(d) Rerun the test

Answer 17

(b) Check the serum for hemolysis

Question 18

Which of the following are true about the anion gap (AG)?

(a) 8-16 mmol/L if K is not used in the calculation
(b) 12-20 mmol/L if K is used in the calculation
(c) The AG can be used as a form a quality control (QC) for the analyzer for Na, K, Cl, and HCO3/Total CO2
(d) All of the above

Answer 18

(d) All of the above

Question 19

What battery of tests is most useful in evaluating an anion gap of 22 mmol/L (22 mEq/L)

(a) AST, ALT, LD, and amylase
(b) BUN/creatinine, salicylate (aspirin) and methanol
(c) Ca+2, Mg+2, PO-4, and pH
(d) CK, myogloin and cryoglobulin

Answer 19

(b) BUN/creatinine, salicylate (aspirin) and methanol

Question 20

When collecting a sample for a lactate lab test the following precautions are needed:

(a) Must be drawn from a fasting patient
(b) No special precautions needed
(c) Phlebotomy drawn with no tourniquet on patient arm and put tube in ice slush once drawn
(d) Draw in an EDTA tube

Answer 20

(c) Phlebotomy drawn with no tourniquet on patient arm and put tube in ice slush once drawn