BMJ  2007;334:693-695 (31 March), doi:10.1136/bmj.39119.607986.47

Practice

Cases in primary care laboratory medicine

Spurious hyperkalaemia

Clinical Laboratory, Bishop Auckland General Hospital, Bishop Auckland DL14 6AD

Although severe hyperkalaemia is life threatening and a medical emergency, spurious hyperkalaemia (pseudohyperkalaemia) is common in blood samples taken in primary care, often because of sampling conditions and storage and transport problems

The first 150 words of the full text of this article appear below.

Introduction

Pseudohyperkalaemia can cause major difficulties in primary care and is a source of avoidable emergency referral and even admission to hospital. It poses a particular problem in the context of out of hours services, when not all patient information is necessarily available to on-call doctors, and is a source of serious concern to patients. This article examines two situations in which apparently alarming hyperkalaemia may occur; it offers guidance to minimise the problem of pseudohyperkalaemia caused by in vitro release of potassium and on identifying the less common causes due to other disease.

Summary points True hyperkalaemia is rare in the presence of normal renal function Difficult venepuncture, cold storage, and deterioration of the sample all raise the serum potassium concentration and warm ambient temperature can lower it Thrombocytosis can raise serum potassium Severe leucocytosis can either raise or lower serum potassium depending on temperature conditions Repeat sampling when results are . . . [Full text of this article]

Case 1

Case 2

Discussion

Problems in samples
Box 1: Causes of pseudohyperkalaemia
Problems in patients
Box 2: What should I do about raised serum potassium?
Box 3: What should I do if I suspect raised serum potassium is spurious?

Evidence note

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This article has been cited by other articles:

• Bailey, I. R, Thurlow, V. R (2008). Is suboptimal phlebotomy technique impacting on potassium results for primary care?. Ann Clin Biochem 45: 266-269 [Abstract] [Full text]  
• Carabine, E. (2008). Minimizing pseudohyperkalaemia in blood samples from general practice. InnovAiT 1: 397-402 [Abstract] [Full text]  

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