Discriminant Validity of the Multiple Errands Test in Schizophrenia

Schizophrenia (SZ) is a chronic, severe disease resulting in a misperception of reality, major social withdrawal and cognitive disturbances. Executive dysfunctions are widely considered as primary determinants of functional outcome. However, classic neuropsychological executive function measures poorly represent patients' functional outcome and seem inappropriate to evaluate the real-world functional impact of the disease.

In this perspective, Shallice and Burgess have developed for brain-damaged patients, the Multiple Errands Test (MET) allowing to assess planning, adaptation, problem solving and mental flexibility in real life settings, thus better capturing day-to-day abilities and including contextual (social, perceptive) influences. Setting the assessment outside the laboratory can help to identify subtle executive impairment not systematically expressed in standard care conditions and consequently improve the future care solutions. MET is based on the Supervisory Attentional System model of executive functioning and attention control that specifies how thought and action schema become activated or suppressed for routine and non-routine circumstances.

MET has been designed to measure real-world executive performance confronting the participants to unpredictable affordances and interpersonal interactions while planning and problem solving. Patients are asked to accomplish several tasks of variable complexity in an unknown commercial district. Severals rules must be respected and thus an action plan, strategy formulation, time and space management with very little assistance of the examiner are required.

Most of the studies involving MET were conceived for patients with acquired brain damage. LeThiec offered an extensive protocol with the initial scoring system (in terms of inefficiencies, rule breaks, interpretation failures and task execution failures). Simplified versions of MET were also suggested to be more suitable in hospital settings. Only one study was done in SZ including a single patient, it is therefore difficult to draw conclusions about clinical utility in SZ. To date, no other studies investigated the suitability of MET in patients with psychosis, while executive impairment is well documented in this population The investigators hypothesized that the Multiple Errands Test (MET), an ecological assessment of executive function has a better ability to measure everyday adaptative functioning SZ, compared to conventional EF assessment methods.