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CHAPTER 1: CONCEPTS IN LABORATORY MEDICINE

1. Which of the following compounds is described in SI units?

A. 4.3 g/dL albumin

B. 0.6 mg/dL bilirubin

C. 1.2 ng/mL digoxin

D. 80 μmol/L creatinine

The correct answer is D. Answer A is incorrect because the SI units for albumin would be in g/L. Answer B is incorrect because the units are not in molar values. The same is true for answer C.

2. Which of the following blood collection vacuum tubes does not contain an anticoagulant?

A. Blue top tube

B. Purple top tube

C. Red top tube

D. Green top tube

The correct answer is C. The blue top tube contains the anticoagulant citrate; the purple top tube contains EDTA; and the green top tube contains heparin—all of which are anticoagulants.

3. Which of the following fluids is tested in the laboratory after producing a clot in the sample and removing the clot?

A. Serum

B. Cerebrospinal fluid

C. Plasma

D. Pleural fluid

The correct answer is A. Serum is generated by producing a clot in plasma, with subsequent removal of the clot prior to testing. Cerebrospinal fluid and pleural fluid are not clotted prior to analysis.

4. Which of the following compounds is represented by desirable, borderline, and high ranges rather than a traditional reference range based on a Gaussian distribution of values?

A. Sodium

B. Hemoglobin

C. Total cholesterol

D. Thyroid-stimulating hormone

The correct answer is C. Populations that consume large amounts of dietary fat have reference ranges for total cholesterol that are associated with atherosclerotic vascular disease. For that reason, the ranges listed for cholesterol are desirable, borderline, and high. All of the other choices in this question have a reference range established by using the values representing the middle 95% of a healthy population.

5. Which one of the following compounds has different ranges depending on the time of day because of diurnal variation?

A. Total cortisol

B. Total estrogens

C. Prothrombin ...

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