Biochemical A quantitative method to define and classify smell and taste function in normal subjects and in patients with smell and taste dysfunction - Dr. R.I. Henkin
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The Taste and Smell Clinic

March 2018

A quantitative method to define and classify smell and taste function in normal subjects and in patients with smell and taste dysfunction


At present there is no accepted method by which smell and taste function can be quantitated to describe, differentiate and classify normal from abnormal smell or taste function.

We have described such a method. This allows differentiation and classification of normal from abnormal smell and taste function in a quantitative manner.

To develop such a technique we defined a method to determine the role of each component of these two sensory systems — their receptors, the brain and the interaction of brain with receptors.

We developed a three stimuli, forced-choice staircase technique with one stimulus compared to two blank standards, a tripartite design. For smell we used a sniff technique, for taste we used a drop technique. Smell stimuli were multiple dilutions of pyridine for pungent, nitrobenzene for sweet, thiophene for petroleum and amyl acetate for banana oil. Taste stimuli were multiple dilutions of NaCl for salt, sucrose for sweet, HCl for sour and urea for bitter.

By use of this tripartite psychophysical presentation we determined four parameters of sensory function: 1) Detection thresholds (DT) quantitation of presence of sensory receptors, 2) Recognition thresholds (RT) quantitation of role of brain, 3) Magnitude estimation (ME) determination of the number of active sensory receptors, 4) Hedonics (H) determination of interactions between sensory receptors and the brain.

Parameter Definitions

  • DT the lowest concentration of substance detected as different from the two blanks, in bottle units (BU)
  • RT the lowest concentration of substance correctly recognized as that substance, in bottle units (BU)
  • ME the mean of all correct recognitions, in percent
  • H the arithmetic mean of all correct recognitions, in percent, averaging both positive and negative responses

Based upon these concepts smell and taste function can be quantitated and subjects classified as either normal or abnormal:

  • Normal sensory function: DT≥5, RT≥2, ME≥50, H varies (pyridine, thiophene, HCl and urea ≥-25 and nitrobenzene, amyl acetate and sucrose ≥ +25).
  • Anosmia or ageusia, total loss of smell or taste, the most severe loss of smell or taste function: DT=0, RT=0, ME=0, H=0.
  • Type I hyposmia or hypogeusia, the next most severe loss of smell or taste function: DT>0, RT=0, ME=0, H=0.
  • Type II hyposmia or hypogeusia, the next most severe loss of smell or taste function: DT>0<5, RT>0<2, ME>0<50, H>0<variable.
  • Type III hyposmia or hypogeusia, the least severe loss of smell or taste function: DT≥5, RT≥2, ME>0<50, H is variable.

Using these quantitative measurements it is possible to compare, quantitate and classify smell and taste function in normal subjects and in patients with smell and taste dysfunction. By these techniques it is also possible to monitor changes in sensory function in patients on treatment for their sensory dysfunction.

For details see: Henkin RI, Levy LM, Fordyce A. Taste and smell function in chronic disease: A review of clinical and biochemical evaluation of taste and smell dysfunction in over 5000 patients at The Taste and Smell Clinic in Washington, DC. Am J Otolaryngol. 2013;34:477-489.


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