Optimizing the month of the year backwards test for delirium screening of older patients in the emergency department.

INTRODUCTION: Different scoring methods exist for the Month of the Year Backward Test (MBT), which is designed to detect inattention, the core feature of delirium. When used as a part of the modified Confusion Assessment Method for the Emergency Department (mCAM-ED), each error in the MBT scores one point. Because this scoring procedure is complex, we aimed to simplify the scoring method of the MBT.

METHODS: This is a secondary analysis of a single center prospective validation study of the mCAM-ED comprising a sample of Emergency Department (ED) patients aged 65 or older presenting to our ED.

DATA COLLECTION: Research assistants (RAs) who were trained nurses conducted the MBT. Geriatricians conducted the reference standard delirium assessment within 1 h of the RA.

RESULTS: For the scoring method "number of errors", optimal performance according the Youden index was achieved when 8 or more errors were reached resulting in an overall sensitivity of 0.95 and overall specificity of 0.94. The scoring method "number of errors in combination with time needed" resulted in a comparable result with minimally lower positive likelihood ratios. For the scoring method "last month in correct order", optimal performance according the Youden index was achieved with the month of September resulting in an overall sensitivity of 0.90 and an overall specificity of 0.89.

DISCUSSION: We suggest omitting the factor time and using a more practical scoring method with good performance: "last month in correct order" with the requirement to reach September to rule out delirium.