Raised LDH (lactate dehydrogenase) found on routine tests

Laboratory tests

• LDH (repeat on a non-haemolysed sample)
• FBC
• Creatine kinase (CK)
• Reticulocyte count (if anaemia)if needednon-French guidelineAnaemia on FBC: haemolysis is excluded by reticulocytes, LDH and haptoglobin ^[1].
• Haptoglobin (if anaemia)if needednon-French guidelineAnaemia on FBC: haemolysis is excluded by reticulocytes, LDH and haptoglobin ^[1].
• Bilirubin (total and conjugated) (if anaemia)if needednon-French guidelineAnaemia: a mainly unconjugated bilirubin, with anaemia, prompts a search for haemolysis ^[1].
• ASTif needednon-French guidelineLDH remaining raised without cause: a British clinical biochemistry review (2024) proposes liver function tests as first line, the liver being a frequent source of LDH ^[2]. No French recommendation on this point: option based on this authors’ opinion.
• ALTif needednon-French guidelineLDH remaining raised without cause: a British clinical biochemistry review (2024) proposes liver function tests as first line, the liver being a frequent source of LDH ^[2]. No French recommendation on this point: option based on this authors’ opinion.
• GGTif needednon-French guidelineLDH remaining raised without cause: a British clinical biochemistry review (2024) proposes liver function tests as first line, the liver being a frequent source of LDH ^[2]. No French recommendation on this point: option based on this authors’ opinion.
• Alkaline phosphataseif needednon-French guidelineLDH remaining raised without cause: a British clinical biochemistry review (2024) proposes liver function tests as first line, the liver being a frequent source of LDH ^[2]. No French recommendation on this point: option based on this authors’ opinion.
• Serum creatinine with eGFR (if LDH remains high without obvious cause)if needednon-French guidelineLDH remaining raised without cause: the same British review (2024) also proposes renal function as first line ^[2]. No French recommendation on this point: option based on this authors’ opinion.
• Clean venepuncture, without prolonged tourniquet; rapid transport to the laboratory. State “repeat of a high LDH: report any haemolysis of the sample”.