A novel test to differentiate anosmic malingerers from actually anosmic patients

The available olfactory evaluation tests are mainly subjective methods requiring patients' collaboration. If, for any reason, the patients refuse to honestly report what they perceive, the test reliability will be questionable; this condition is potentially observable in malingering patients because of their financial or psychosocial incentives. In an olfactory discrimination test context, this study was aimed to design a test capable of distinguishing malingerer from actually anosmic or severely hyposmic patients.

The pilot experiment of our methodology study determined five substances (coffee, lemon, rosewater, thyme, and garlic) as qualified odors of a 20-item odor discrimination test and set its normal reference value at 15. Through two simulations, 70 normosmic participants emulated actual anosmia and also malingering. The outcome results were used to measure test reliability factors.

During the malingering simulation, only seven participants were capable of keeping their scores at the test chance level with enough randomness in their sequences of answers while the actual anosmia simulation revealed that 39 had scores at the test chance level. Accordingly, the Tehran University Odor Discrimination Test (TUODT) was measured to have 90% sensitivity, 55.71% specificity, 67.02% positive predictive value, and 84.78%negative predictive value.

The TUODT is a relatively efficient method to identify anosmia malingerers.