Investigative algorithms for disorders affecting plasma lactate dehydrogenase: a narrative review

Abstract

Background and Objective: The following article is part of a special series to aid the reader in diagnosing the cause of various plasma derangements in humans. By the end of the article, the reader will be able to order and interpret appropriate investigations when faced with a patient with low or high lactate dehydrogenase (LDH) activity in plasma. Methods: A narrative, focused literature review was performed using Medline, OMIM and Google Scholar from April 2023 to September 2023 to identify references published from database inception to September 2023; reference lists from these articles were also used. The language was restricted to English. Key Content and Findings: LDH is produced by all cells and can be released into plasma in a vast number of pathological processes. Liver and red blood cells are a common source as is skin, lung, muscle, and the gastrointestinal tract. A laboratory approach to the investigation of elevated LDH is presented, no algorithm was produced for low LDH activity as causes are too scarce and of unlikely clinical significance. The clinical status and condition of the patient should be considered first in order to carry out a targeted investigation however full blood count, liver and renal function tests may be used as first line tests. Conclusions: Diagnostic flow charts have been created to help aid healthcare professionals to investigate the cause of elevated LDH activity where the cause is not immediately apparent. These algorithms have been presented and created within the limitations of the laboratory tests discussed within the paper, selected to be widely available.