Background: The Miller Forensic Assessment of Symptoms Test (M-FAST)  was originally developed for detection of malingering of psychiatric symptoms in forensic settings, but it is now used frequently on other clinical groups such as post-accident patients or war veterans, to assess malingering of non-psychiatric medical symptoms, i.e., on patient groups and on symptoms for which the M-FAST was not validated in accordance with standards of the American Psychological Association (APA).
Method: The M-Fast consists only of 25 items. We undertook a systematic review of all 25 items to evaluate their content validity, i.e., congruence with the intended goal to differentiate malingerers from legitimate patients.
Results: With respect to detection of malingering of psychiatric symptoms, the M-FAST items list many legitimate psychiatric symptoms that are (rather perplexingly) scored as indicators of malingering. A few examples are as follows: auditory hallucinations (“voices”) associated with autonomic signs of anxiety (Item 18) or with fear of leaving the room or home during such episodes (Item 22), hallucinations lasting for days (Item 6), and olfactory hallucinations (phantosmia) (Item 17), adverse changes of mood while suspecting to be plotted against (Item 3), a belief to have special powers with respect to sensory perception (Item 13), and delusional parasitosis (Item 20). An M-FAST item refers to “feeling depressed most of the time” (Item 2) and is also scored as indicator of malingering.
With respect to detection of malingering of medical symptoms in survivors of motor vehicle accidents (MVA), examples of unduly contaminated item content include: depressed feelings (Item 2), tinnitus triggered or exacerbated over the duration of stressful interview (Item 25), intense nightmares that occur concurrently with weight loss (Item 12), neurological symptom of formication (Item 20), phantosmia (Item 17), and fluctuation of symptoms as if someone is “turning them on and off …” (Item 14).
Discussion and Conclusions: More than a half of M-FAST items have content that can be legitimately endorsed by psychiatric patients, or those injured in MVAs, or by injured war veterans, but in the M-FAST, these items are erroneously scored as indicators of malingering. This can lead to high rates of false positives, e.g., 33% to 63% in the 2017 study by Weiss and Rosenfeld.
Keywords: malingering, M-FAST, thought disorder, delusions, hallucinations, post-concussion syndrome, whiplash syndrome.