Ascertaining instances of neuroleptic malignant syndrome in a secondary mental healthcare electronic medical records database: the SLAM BRC Case Register

Objectives: Neuroleptic malignant syndrome (NMS) is a rare but potentially fatal complication of antipsychotic treatment. However, there is no single diagnostic test and a variety of overlapping criteria exist. Using a large case register of secondary mental healthcare in Southeast London, we aimed to identify suspected cases and quantify the levels of agreement between six different diagnostic criteria previously published. Methods: Taking advantage of a recently developed case register sourced from full but anonymized electronic medical records (the South London and Maudsley NHS Foundation Trust), we applied text string searching to identify suspected NMS cases for which action had been taken to investigate or treat. Three psychiatrists manually reviewed case records for clinical data to compare diagnostic criteria. Results: Analysis of the case register revealed 183 suspected NMS cases, of which 43 fulfilled at least one set of the six diagnostic criteria. Agreement between criteria was poor (κ = 0.35 for all combined agreement; 95% confidence interval 0.31–0.39) and only one case fulfilled all six diagnostic criteria. However, among cases meeting any diagnostic criteria, pyrexia, extrapyramidal symptoms, altered consciousness, autonomic symptoms, and elevated CK concentrations were significantly more common than in cases not meeting diagnostic criteria ( p < 0.01). On further analyses, the presence of two or more of these features significantly distinguished cases meeting criteria from those that did not ( p < 0.01). Individual symptoms were also reported in suspected cases of NMS that did not fulfil any diagnostic criteria. Conclusions: In a large sample of NMS cases recorded in medical records, relatively poor agreement was found among published diagnostic criteria for NMS. However, core features of NMS were observed significantly more often among cases meeting diagnostic criteria. Individual symptoms were also described in suspected cases that did not meet diagnostic criteria. These findings suggest a continued need for consensus on standard criteria for NMS.