Investigative algorithms for disorders affecting plasma chloride: a narrative review

of a special series to aid the reader in diagnosing the cause of various electrolyte imbalances. A focussed literature review will, by the end of this article, enable the reader to correctly order and interpret laboratory tests to investigate derangements in plasma chloride. Methods: A narrative, focused literature review was performed of English language resources using PubMed, OMIM and Google. References published from database inception to January 2022 were searched for during September 2021 to January 2022. Further articles were identified from reference lists. Key Content and Findings: Chloride concentration can be affected by changes in acid base status and is closely linked to sodium homeostasis. Hyperchloraemia is most commonly due to water loss and associated with hypernatraemia, mismatch may indicate a spurious result. Hypochloraemia is associated with metabolic alkalosis and renal salt-losing tubulopathies. Although 24-hour urine chloride collections can be used to aid diagnosis the range of variables affecting results makes it controversial and results should only be interpreted with caution. Conclusions: Diagnostic schema will be presented, and the limitations of the laboratory tests discussed. By provision of diagnostic algorithms investigation choice and interpretation is supported allowing healthcare professionals to confirm clinical diagnoses and more expertly review the most complex cases.