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Normal potassium in the presence of gross hemolysis.

CASE DESCRIPTION

A 15-year-old boy presented to the emergency department with acute development of fever and chills. Physical exam revealed a blood pressure of 86/61, jaundice with scleral icterus, and dark urine. Laboratory tests (increased free hemoglobin, increased lactate dehydrogenase, and decreased haptoglobin) revealed a direct antiglobulin test (DAT)negative hemolytic anemia. Sequential serum potassium measurements remained normal to low (reference interval, 3.6-5.2 mmol/L) through the majority of his disease course (Fig. 1).

[FIGURE 1 OMITTED]

QUESTIONS FOR DISCUSSION

1. How would you expect gross hemolysis to affect the serum potassium concentration?

2. What caused the normal serum potassium in the setting of hemolysis?

3. What medical conditions can cause DAT-negative hemolytic anemia?

The answers are on the next page.

Answers

Hemolysis releases intracellular potassium. For hemolysis occurring after the sample is drawn, the serum potassium would appear artificially high (1, 2). However, when hemolysis occurs in vivo (e.g., a hemolytic anemia), the patient's potassium-regulating systems will quickly normalize the serum potassium to prevent hyperkalemia (3). Some possible causes of DAT-negative hemolysis include thrombotic thrombocytopenic purpura/hemolytic uremic syndrome, disseminated intravascular coagulation, infection (e.g., malaria), drug- or toxin-induced hemolysis, hypersplenism, and Wilson disease (4).

Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.

Authors' Disclosures or Potential Conflicts of Interest: No authors declared any potential conflicts of interest.

References

(1.) Asirvatham JR, Moses V, Bjornson L. Errors in potassium measurement: a laboratory perspective for the clinician. N Am J Med Sci 2013; 5:255-9.

(2.) Zou J, Nolan DK, LaFiore AR, Scott MG. Estimating the effects of hemolysison potassium and LDH laboratory results. Clin Chim Acta 2013; 421:60-1.

(3.) Khodorkovsky B, Cambria B, Lesser M, Hahn B. Do hemolyzed potassium specimens need to be repeated? J Emerg Med 2014; 47:313-7.

(4.) Kok VC, Lee CK, Horng JT, Lin CC, Sung FC. Reappraisal of the etiology of extracorpuscular non-autoimmune acquired hemolyticanemia in 2657 hospitalized patients with non-neoplastic disease. Clin Med Insights Pathol 2014; 7:11-4.

Mary M. Barrett and Y. Victoria Zhang *

Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, NY.

* Address correspondence to this author at: Y. Victoria Zhang, Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, 601 Elmwood Ave, Box 608, Rochester, NY 14642. E-mail victoria_zhang@urmc.rochester.edu.

Received January 21, 2015; accepted April 2, 2015.

DOI: 10.1373/clinchem.2015.238899

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Article Details
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Title Annotation:What Is Your Guess?
Author:Barrett, Mary M.; Zhang, Y. Victoria
Publication:Clinical Chemistry
Article Type:Report
Geographic Code:1USA
Date:Aug 1, 2015
Words:446
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