Utility and limitations of the traditional diagnostic approach to hyponatremia: a diagnostic study
Wiebke Fenske, Sebastian Maier, Anne Blechschmidt, Stefan Störk & Bruno Allolio
Background: The differential diagnosis of hyponatremia is often challenging because of its association with multiple underlying pathophysiological mechanisms, diseases and treatment options. Several algorithms are available in order to guide the diagnostic approach to hyponatremia, but their diagnostic and clinical utility has never been evaluated. We aimed to assess in detail the diagnostic utility as well the limitations of the existing approaches to hyponatremia.
Methods: Each of the 121 consecutive subjects presenting with hyponatremia (serum sodium <130 mmol/l) underwent three different and independent diagnostic and therapeutic approaches: i) unexperienced doctor applying an established Algorithm, ii) intensive care senior physicians acting as Senior Physician, and iii) senior endocrinologist serving as Reference Standard.
Results: The overall diagnostic agreement between Algorithm and Reference Standard was 71% (respective Cohens κ and δ values were 0.64 and 0.70), the overall diagnostic agreement between Senior Physician and Reference Standard was 32% (0.20 and 0.19). Regarding the therapeutic consequences, the diagnostic accuracy of the Algorithm and the Senior Physician was 86% (0.70 and 0.72) and 48% (0.01 and 0.04), respectively. In retrospect, by disregarding patients extracellular fluid volume and assessing the effective arterial blood volume by determination of the fractional urate excretion, the Algorithm improved its diagnostic accuracy to 95%.
Conclusion: Although the Algorithm performed reasonably well, several shortcomings became apparent, rendering it difficult to apply the Algorithm without reservation. Whether some modifications may enhance its diagnostic accuracy and simplify the management of hyponatremia needs to be determined.