Months backward test: A review of its use in clinical studies

Abstract

AIM: To review the use of the Months Backwards Test (MBT) in clinical and research contexts.

METHODS: We conducted a systematic review of reports relating to the MBT based upon a search of PsychINFO and MEDLINE between January 1980 and December 2014. Only reports that specifically described findings pertaining to the MBT were included. Findings were considered in terms of rating procedures, testing performance, psychometric properties, neuropsychological studies and use in clinical populations.

RESULTS: We identified 22 data reports. The MBT is administered and rated in a variety of ways with very little consistency across studies. It has been used to assess various cognitive functions including focused and sustained attention as well as central processing speed. Performance can be assessed in terms of the ability to accurately complete the test without errors (“MB accuracy”), and time taken to complete the test (“MB duration”). Completion time in cognitively intact subjects is usually < 20 s with upper limits of 60-90 s typically applied in studies. The majority of cognitively intact adults can complete the test without error such that any errors of omission are strongly suggestive of cognitive dysfunction. Coverage of clinical populations, including those with significant cognitive difficulties is high with the majority of subjects able to engage with MBT procedures. Performance correlates highly with other cognitive tests, especially of attention, including the digit span backwards, trailmaking test B, serial threes and sevens, tests of simple and complex choice reaction time, delayed story recall and standardized list learning measures. Test-retest and inter-rater reliability are high (both > 0.90). Functional magnetic resonance imaging studies comparing the months forward test and MBT indicate greater involvement of more complex networks (bilateral middle and inferior frontal gyri, the posterior parietal cortex and the left anterior cingulate gyrus) for backwards cognitive processing. The MBT has been usefully applied to the study of a variety of clinical presentations, for both cognitive and functional assessment. In addition to the assessment of major neuropsychiatric conditions such as delirium, dementia and Mild Cognitive Impairment, the MBT has been used in the assessment of concussion, profiling of neurocognitive impairments in organic brain disorders and Parkinson’s disease, prediction of delirium risk in surgical patients and medication compliance in diabetes. The reported sensitivity for acute neurocognitive disturbance/delirium in hospitalised patients is estimated at 83%-93%. Repeated testing can be used to identify deteriorating cognitive function over time.

CONCLUSION: The MBT is a simple, versatile tool that is sensitive to significant cognitive impairment. Performance can be assessed according to accuracy and speed of performance. However, greater consistency in administration and rating is needed. We suggest two approaches to assessing performance - a simple (pass/fail) method as well as a ten point scale for rating test performance (467).

Keywords: Cognition; Assessment; Months backward test; Delirium; Dementia

Core tip: The months backward test is a brief test of cognitive function that is commonly used in clinical practice. It provides a convenient test of central processing speed and both focused and sustained attention. This review of studies reporting its use in clinical populations identified many different approaches to administration and interpretation of the test. Overall, cognitively intact adults can complete the test within 60 s without omission errors, such that failure to achieve this is strongly suggestive of cognitive dysfunction. The sensitivity for neurocognitive disturbance in hospitalised patients is 83%-93% and repeated testing can identify deteriorating cognitive function over time.