Aim The aim of our investigation was to review the use of serum lactate dehydrogenase (LDH) testing in the Paediatric Emergency Department and to develop an appropriate algorithm for its use.

Methods We obtained case records of patients that had serum LDH measured in the Department over a 3 year period and examined the justification and result of each test and any subsequent change in management.

Results 62 children had serum LDH requested during the period, with results available for 59 (one was haemolysed, and two had no result available). There was a wide range of clinical presentations among the cases, but the top 5 indications are shown in table 1, which encompasses 83% of the total. A raised level (>243 μ/l) was found in 20 cases (34%), range 244 u/l to 1139 u/l, mean 391 u/l. The majority of these were only mildly elevated, but there were three cases with levels >500 u/l – acute lymphoblastic leukemia, sepsis induced hepatitis and infectious mononucleo sis (none required LDH for diagnosis). In 42 cases (71%) there appeared to be no clinical justification for the test. In the other 17 cases (29%), there was arguably some clinically relevant indication for the test (eg, abdominal mass, persisting lymphadenopathy). However in none of these cases did the LDH result appear to affect management in any way.

Conclusion We identified a small number of LDH requests during the study period, a high proportion of which were performed without justification. Serum LDH as a diagnostic marker, has low specificity and sensitivity and its utility in most clinical scenarios is very limited. Unless levels are extremely high it rarely contributes to patient diagnosis. We believe that indiscriminate use of serum LDH may lead to unnecessary investigations and parental anxiety if elevated, and a false sense of security if not. LDH should only be measured in cases where there is a significant suspicion of malignancy, but should not be used in isolation even in that situation to determine further management.