Pseudohyponatraemia : a literature review

Abstract

Hyponatraemia often poses a diagnostic dilemma, brought about by inadequate work-up and inappropriate management. In order to make the correct diagnosis, an understanding of the pathophysiology and classification of hyponatraemia is essential. In this review, focus is made on the diagnosis of pseudohyponatraemia including the causes, when to suspect it and how to diagnose it. Different analytical methods are discussed, including flame emission spectrophotometry, and ion-specific electrode (ISE) potentiometry and the role they play in diagnosing pseudohypopatraemia. The measured and calculated osmolalities and their use to calculate the osmolal gap are explained. Finally, a discussion follows on the aetiologies of pseudohyponatraemia, strategies to circumvent this problem and the relevance of clinching the diagnosis in clinical practice.