Chemistry, toxicology & urinalysis

A 17 year old unrestrained male passenger of a motor vehicle accident arrived at the emergency department with multiple fractures of the bilateral upper and lower extremities, hematomas and contusions. The patient exhibited signs of confusion and lethargy. The presence of nonpurulent serous drainage from the nose was concerning as it could indicate a cerebrospinal fluid leak from a suspected cranial trauma. What is the most specific test to determine the source of the rhinorrhea?

1. β2 transferrin
2. β trace protein
3. Glucose
4. Radionuclide cisternography
5. Ring sign

A. β2 transferrin. β2 transferrin is a transferrin variant found in cerebrospinal fluid (CSF), perilymph of the ear and vitreous humor of the eye. It is a highly specific marker for CSF. Answer D is incorrect because radionucleotide cisternography is very specific for identifying a CSF leak; however, it cannot distinguish between a rhinologic versus an otologic source. Answer B is incorrect because β trace protein, although shown in some studies to rival β2 transferrin in specificity and sensitivity, is also present in blood. In certain patient groups, β trace protein is decreased and should not be used. Answer E is incorrect because ring sign is a visible halo sometimes found at the bedside of patients with bloodstains mixed with CSF. It has poor specificity for CSF detection. Answer C is incorrect because although the use of glucose testing strips on rhinorrhea specimens was once thought to be a positive indication of the presence of CSF, studies have shown that glucose can be detected in otherwise healthy patients. The detection of glucose in rhinorrhea is not considered sensitive or specific for CSF (Int Forum Allergy Rhinol 2016;6:8).

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Reference: Transferrin

An 18 year old woman with past medical history of sickle cell trait, iron deficiency and neutropenia presents to the office for follow up. She states that she has been having right lower quadrant pain for the past week. The pain can become so severe that she rates it at 7/10. It causes nausea and abdominal fullness. She denies fever, colicky pain or flank pain. The patient serum transferrin concentration is 390 mg/dL (normal: 200 mg/dL to 360 mg/dL). Which of the following is most likely observed in this patient?

1. Ferritin concentration of 10 ng/mL
2. Ferritin concentration of 200 ng/mL
3. Iron concentration of 100 μg/dL
4. Iron saturation 80%
5. Total iron binding capacity of 200 μg/dL

A. Ferritin concentration of 10 ng/mL. Understanding the normal ranges for transferrin, iron saturation, iron concentration and TIBC will demonstrate that normal ferritin concentration in women is 24 to 307 ng/mL. The patient has a history of anemia and presents with an elevated transferrin; therefore, the ferritin concentration should be decreased. Answers B, C, D and E are incorrect because these responses are consistent with normal iron levels.

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Reference: Transferrin

Hypertransferrinemia can be seen in patients with

1. Acute myocardial infarction
2. Cirrhosis
3. Hypoalbuminemia
4. Iron deficiency
5. Nephrotic syndrome

D. Iron deficiency. Iron deficiency is the only option that is compatible with an elevated transferrin level. Answer C is incorrect because hypotransferrinemia usually accompanies hypoalbuminemia and is also an indication of protein malnutrition. Answer E is incorrect because nephrotic syndrome causes loss of proteins such as transferrin. Answer B is incorrect because cirrhosis results in decreased production of all proteins synthesized in the liver. Answer A is incorrect because hypotransferrinemia is associated with acute myocardial infarction rather than normal or excess transferrin. Transferrin is also a negative acute phase reactant and would be decreased in the hours and days following an acute event such as an infarction.

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Reference: Transferrin