Laboratory Values (saunders NCLEX book)

Question 1

A client was transferred to the nursing unit from the coronary care unit after experiencing a myocardial infarction (MI). When reviewing the client’s serum creatinine phosphokinase (CPK) levels recorded in the chart, the nurse knows that an elevation of which of the following was due to the MI?

1. MB
2. MM
3. MK
4. BB

Answer 1

MB
**Rationale: CPK is a cellular enzyme that can be fractionated into three isoenzymes. The MB band reflects CPK from cardiac muscle. This is the level that elevates with MI. The MM band reflects CPK from skeletal muscle. The BB band reflects CPK from the brain. There is no MK band.
Test-Taking Strategy: Focus on the subject, the laboratory value that indicates an MI. Remember that the CPK-MB reflects the cardiac muscle. Review this laboratory value for detecting MI if you had difficulty with this question.

Question 2

A client with history of seizure disorder is having a routine serum phenytoin level drawn. The nurse who receives a telephone report of the results notes that the client’s blood level of the medication is within the normal range if the value reported is:

1. 15 mcg/mL
2. 6 mcg/mL
3. 28 mcg/mL
4. 35 mcg/mL

Answer 2

15 mcg/mL
**Rationale: The therapeutic range for serum phenytoin (Dilantin) level is 10 to 20 mcg/mL. If the level is below the therapeutic range, the client could experience seizure activity. If the level is too high, the client is at risk for phenytoin toxicity.
Test-Taking Strategy: Focus on the subject, the therapeutic range for serum phenytoin. Remember that the therapeutic range is 10 to 20 mcg/mL. Review this laboratory test if you had difficulty with this question.

Question 3

A long-term-care nurse about to give a daily dose of digoxin (Lanoxin) is told that a serum digoxin level drawn earlier in the day measured 2.7 ng/mL. The nurse should take which of the following actions first?

1. Gather data from the client related to signs of toxicity.
2. Report the finding to the health care provider.
3. Record the normal value on the intershift report sheet.
4. Administer the daily dose of the medication.

Answer 3

Gather data from the client related to signs of toxicity.
**Rationale: The normal therapeutic range for digoxin is 0.5 to 2 ng/mL. A value of 2.7 exceeds the therapeutic range and could be toxic to the client. The nurse should gather data about signs of digoxin toxicity and then notify the health care provider. Option 3 is incorrect because the value is high, not normal. Option 4 is incorrect because the next dose should not be administered automatically.
Test-Taking Strategy: Note that the question contains the strategic word “first.” Recalling that the normal therapeutic range for digoxin is 0.5 to 2 ng/mL will direct you to the correct option. If this question was difficult, review the information on this commonly used medication and measurement of its therapeutic serum level.

Question 4

A licensed practical nurse (LPN) is assisting in the care of a client receiving a continuous intravenous (IV) infusion of heparin sodium for deep vein thrombosis (DVT). The LPN notes that the result of a newly drawn activated partial thromboplastin time (aPTT) level is 90 seconds. The client’s baseline before the initiation of therapy was 30 seconds. The LPN should take which of the following actions?

1. Leave the report for the registered nurse (RN) to review later in the day.
2. Ask the client about worsening pain from the DVT.
3. Notify the RN about the value immediately.
4. Check to see if additional heparin is available on the unit.

Answer 4

Notify the RN about the value immediately.
**Rationale: The normal aPTT varies between 20 and 36 seconds, depending on the type of activator used in testing. Heparin treatment for DVT aims to keep the aPTT between 1.5 and 2.5 times normal. Thus, the client’s aPTT is elevated (75 is the upper therapeutic value for this client, given the baseline). The LPN should report the findings immediately to the RN, who will take further action to follow up on the elevated value. Option 1 puts the client at risk for bleeding. Option 2 is unrelated to the question. Option 4 is incorrect because it implies that the reported value is low.
Test-Taking Strategy: Focus on the data in the question. Recalling that the normal aPTT varies between 20 and 36 seconds will direct you to option 3. Review this laboratory test and its relationship to administering heparin if you had difficulty with this question.

Question 5

A client is receiving oral anticoagulant therapy with warfarin (Coumadin). The result of a newly drawn prothrombin time (PT) is 28 seconds. The nurse anticipates carrying out an order to:

1. Hold the next dose of warfarin.
2. Stop the warfarin and administer heparin.
3. Administer the next dose of warfarin.
4. Increase the next dose of warfarin.

Answer 5

Hold the next dose of warfarin.
**Rationale: The normal PT is 9.6 to 11.8 seconds for adult men and 9.5 to 11.3 seconds for adult women. The therapeutic PT level is approximately 1.3 to 1.5 times greater than the client’s control level. Because the value stated is extremely high, the nurse should anticipate that the client would not receive further doses at this time. If the level were too high, then the antidote (vitamin K) could also be prescribed. It would be dangerous to add a different anticoagulant to the client’s regimen at this time (option 2).
Test-Taking Strategy: Focus on the data in the question. Recalling that the normal PT is 9.6 to 11.8 seconds for adult men and 9.5 to 11.3 seconds for adult women will direct you to option 1. Review this laboratory test and its relationship to administering warfarin if you had difficulty with this question.

Question 6

An adult client has had serum electrolytes drawn. The nurse receiving the results by telephone from the laboratory would be most concerned with which of the following results?

1. Chloride 103 mEq/L
2. Bicarbonate 24 mEq/L
3. Sodium 142 mEq/L
4. Potassium 5.4 mEq/L

Answer 6

Potassium 5.4 mEq/L
**Rationale: The normal serum electrolyte ranges for adults are sodium, 136 to 145 mEq/L; potassium, 3.5 to 5.1 mEq/L; chloride, 98 to 107 mEq/L; and bicarbonate (venous), 22 to 29 mEq/L. The only abnormal value identified above is the serum potassium, which would be the one of most concern to the nurse.
Test-Taking Strategy: Focus on the data in the question. Recalling that the normal potassium range is 3.5 to 5.1 mEq/L will direct you to option 4. Review the normal electrolyte levels if you had difficulty with this question.

Question 7

A nurse is providing directions to a client about how to test a stool for occult blood. The nurse cautions that which of the following could cause a false-negative result?

1. Iodine
2. Acetylsalicylic acid
3. Ascorbic acid
4. Colchicine

Answer 7

Ascorbic acid
**Rationale: Ascorbic acid can interfere with results of occult blood testing, yielding false-negative results. Colchicine and iodine can cause false-positive results. Acetylsalicylic acid either would have no effect or could cause a positive result by inducing bleeding from the gastrointestinal tract.
Test-Taking Strategy: Focus on the subject, a false-negative result. Remember that ascorbic acid can interfere with results of occult blood testing, yielding false-negative results. Review this laboratory test if you had difficulty with this question.

Question 8

An older client has been treated for dehydration and pneumonia. The nurse evaluates that the client’s dehydration has been successfully treated if the blood urea nitrogen (BUN) level drops to:

1. 19 mg/dL
2. 5 mg/dL
3. 46 mg/dL
4. 32 mg/dL

Answer 8

19 mg/dL
**Rationale: The normal BUN for the older adult is 8 to 21 mg/dL. Thus option 1 is correct. Values such as those in options 3 and 4 are high and reflect continued dehydration. Option 2 reflects a lower than normal value, which can occur with fluid overload.
Test-Taking Strategy: Note the strategic words “has been successfully treated.” Recalling that the normal BUN for the older adult is 8 to 21 mg/dL will direct you to option 1. Review this laboratory test if you had difficulty with this question.

Question 9

A nurse is reading a computer printout of the results of a cerebrospinal fluid (CSF) analysis performed on an adult client who underwent lumbar puncture. The nurse knows that a reported value of 0 is normal for which of the following substances in CSF?

1. Protein
2. Glucose
3. White blood cells
4. Red blood cells

Answer 9

Red blood cells
**Rationale: The adult with normal CSF has no red blood cells in the CSF. The client may have small numbers of white blood cells (0 to 3/mm3). Protein (15 to 45 mg/dL) and glucose (40 to 80 mg/dL) normally are present in CSF.
Test-Taking Strategy: Note the strategic words “a reported value of 0 is normal.” Remember that the adult with normal CSF has no red blood cells in the CSF. Review the normal findings for CSF if you had difficulty with this question.