Name: taste exam: a brief and validated test
Uploaded: 2018-08-17T12:30:00
Description: Watch this Scientific Journal Video about Taste Exam: A Brief and Validated Test at JoVE.com

Awards from the National Institutes of Health supported this research (R01DC013588 to NAC, R21DC013886 to NAC and DRR, and NIDCD Administrative Research Supplement to Promote Emergence of Clinician-Scientists in Chemosensory Research to JED). We collected genotype data from equipment purchased in part with NIH funds from OD018125.

The University of Pennsylvania Institutional Review board approved this protocol. We excluded subjects if they were under 18 years of age or were pregnant.
1. Oral Cavity Evaluation: Disease Assessment and Papilla Identification
<ol>
	<li>Instruct the subject to open the mouth.</li>
	<li>Using a light source such as a penlight or headlamp, illuminate the oral cavity and examine the seven subsites of the area (tongue, floor of mouth, buccal mucosa, labial mucosa, gingiva, hard palate,...

<ol>
	<li>Cowart, B. J., Young, I. M., Feldman, R. S., Lowry, L. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+disorders+of+smell+and+taste.">Clinical disorders of smell and taste.</a> Occupational Medicine. 12 (3), 465-483 (1997).</li><li>Ackerman, B. H., Kasbekar, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disturbances+of+taste+and+smell+induced+by+drugs.">Disturbances of taste and smell induced by drugs.</a> Pharmacotherapy. 17 (3), 482-496 (1997).</li><li>Kveton, J. F., Bartoshuk, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+unilateral+chorda+tympani+damage+on+taste.">The effect of unilateral chorda tympani damage on taste.</a> Laryngoscope. 104, 25-29 (1994).</li><li>Fischer, R. A., Griffin, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pharmacogenetic+aspects+of+gustation.">Pharmacogenetic aspects of gustation.</a> Drug Research. 14 (14), 673-686 (1964).</li><li>Joyce, C. R., Pan, L., Varonos, D. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Taste+sensitivity+may+be+used+to+predict+pharmacological+effects.">Taste sensitivity may be used to predict pharmacological effects.</a> Life Science. 7 (9), 533-537 (1968).</li><li>Adappa, N. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetics+of+the+taste+receptor+T2R38+correlates+with+chronic+rhinosinusitis+necessitating+surgical+intervention.">Genetics of the taste receptor T2R38 correlates with chronic rhinosinusitis necessitating surgical intervention.</a> International Forum of Allergy &amp; Rhinology. , (2013).</li><li>Lipchock, S. V., Reed, D. R., Mennella, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relationship+between+bitter-taste+receptor+genotype+and+solid+medication+formulation+usage+among+young+children:+a+retrospective+analysis.">Relationship between bitter-taste receptor genotype and solid medication formulation usage among young children: a retrospective analysis.</a> Clinical Therapeutics. 34 (3), 728-733 (2012).</li><li>Bartoshuk, L. M., Carterette, E. C., Friedman, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Handbook of perception: Tasting and smelling. , 2-18 (1978).</li><li>Coldwell, S. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gustation+assessment+using+the+NIH+Toolbox.">Gustation assessment using the NIH Toolbox.</a> Neurology. 80 (11 Suppl 3), S20-S24 (2013).</li><li>Mueller, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+assessment+of+gustatory+function+in+a+clinical+context+using+impregnated+&amp;#34;taste+strips&amp;#34.">Quantitative assessment of gustatory function in a clinical context using impregnated &amp;#34;taste strips&amp;#34.</a> Rhinology. 41 (1), 2-6 (2003).</li><li>Reed, D. R., Tanaka, T., McDaniel, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diverse+tastes:+Genetics+of+sweet+and+bitter+perception.">Diverse tastes: Genetics of sweet and bitter perception.</a> Physiological Behavior. 88 (3), 215-226 (2006).</li><li>Miller, I. J., Reedy, F. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Variations+in+human+taste+bud+density+and+taste+intensity+perception.">Variations in human taste bud density and taste intensity perception.</a> Physiological Behavior. 47 (6), 1213-1219 (1990).</li><li>Shahbake, M., Hutchinson, I., Laing, D. G., Jinks, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+quantitative+assessment+of+fungiform+papillae+density+in+the+human+tongue.">Rapid quantitative assessment of fungiform papillae density in the human tongue.</a> Brain Research. 1052 (2), 196-201 (2005).</li><li>Spielman, A. I., Pepino, M. Y., Feldman, R., Brand, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Technique+to+collect+fungiform+(taste)+papillae+from+human+tongue.">Technique to collect fungiform (taste) papillae from human tongue.</a> Journal of Visualized Experiments. 18 (42), 2201 (2010).</li><li>Nuessle, T. M., Garneau, N. L., Sloan, M. M., Santorico, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Denver+papillae+protocol+for+objective+analysis+of+fungiform+papillae.">Denver papillae protocol for objective analysis of fungiform papillae.</a> Journal of Visualized Experiments. (100), e52860 (2015).</li><li>Sanyal, S., O'Brien, S. M., Hayes, J. E., Feeney, E. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TongueSim:+development+of+an+automated+method+for+rapid+assessment+of+fungiform+papillae+density+for+taste+research.">TongueSim: development of an automated method for rapid assessment of fungiform papillae density for taste research.</a> Chemical Senses. 41 (4), 357-365 (2016).</li><li>Spielman, A. I., Brand, J. G., Buischi, Y., Bretz, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resemblance+of+tongue+anatomy+in+twins.">Resemblance of tongue anatomy in twins.</a> Twin Research and Human Genetics. 14 (3), 277-282 (2011).</li><li>Kalmus, H., Smith, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+antimode+and+lines+of+optimal+separation+in+a+genetically+determined+bimodal+distribution,+with+particular+reference+to+phenylthiocarbamide+sensitivity.">The antimode and lines of optimal separation in a genetically determined bimodal distribution, with particular reference to phenylthiocarbamide sensitivity.</a> Annals of Human Genetics. 29 (2), 127-138 (1965).</li><li>Pearson, J., Finegold, M. J., Budzilovich, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+tongue+and+taste+in+familial+dysautonomia.">The tongue and taste in familial dysautonomia.</a> Pediatrics. 45 (5), 739-745 (1970).</li><li>Fukutake, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Late-onset+hereditary+ataxia+with+global+thermoanalgesia+and+absence+of+fungiform+papillae+on+the+tongue+in+a+Japanese+family.">Late-onset hereditary ataxia with global thermoanalgesia and absence of fungiform papillae on the tongue in a Japanese family.</a> Brain. 119 (Pt 3), 1011-1021 (1996).</li><li>Kinnamon, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Taste+receptor+signalling+-+from+tongues+to+lungs.">Taste receptor signalling - from tongues to lungs.</a> Acta physiologica. 204 (2), 158-168 (2012).</li><li>Lewandowski, B. C., Sukumaran, S. K., Margolskee, R. F., Bachmanov, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amiloride-insensitive+salt+taste+is+mediated+by+two+populations+of+type+iii+taste+cells+with+distinct+transduction+mechanisms.">Amiloride-insensitive salt taste is mediated by two populations of type iii taste cells with distinct transduction mechanisms.</a> Journal of Neuroscience. 36 (6), 1942-1953 (2016).</li><li>Vandenbeuch, A., Clapp, T. R., Kinnamon, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amiloride-sensitive+channels+in+type+I+fungiform+taste+cells+in+mouse.">Amiloride-sensitive channels in type I fungiform taste cells in mouse.</a> BMC Neuroscience. 9, 1 (2008).</li><li>Margolskee, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+biochemistry+and+molecular+biology+of+taste+transduction.">The biochemistry and molecular biology of taste transduction.</a> Current Opinions in Neurobiology. 3 (4), 526-531 (1993).</li><li>Meyerhof, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+molecular+receptive+ranges+of+human+TAS2R+bitter+taste+receptors.">The molecular receptive ranges of human TAS2R bitter taste receptors.</a> Chemical Senses. 35 (2), 157-170 (2010).</li><li>Yee, K. K., Sukumaran, S. K., Kotha, R., Gilbertson, T. A., Margolskee, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glucose+transporters+and+ATP-gated+K++(KATP)+metabolic+sensors+are+present+in+type+1+taste+receptor+3+(T1r3)-expressing+taste+cells.">Glucose transporters and ATP-gated K+ (KATP) metabolic sensors are present in type 1 taste receptor 3 (T1r3)-expressing taste cells.</a> Proceedings of the National Academy of Sciences USA. , (2011).</li><li>Tordoff, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium:+taste,+intake+and+appetite.">Calcium: taste, intake and appetite.</a> Physiological Review. 81, 1567-1597 (2001).</li><li>Reed, D. R., Xia, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+fatty+acid+perception+and+genetics.">Recent advances in fatty acid perception and genetics.</a> Advances in Nutrition. 6 (3), 353S-360S (2015).</li><li>Blekhman, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Host+genetic+variation+impacts+microbiome+composition+across+human+body+sites.">Host genetic variation impacts microbiome composition across human body sites.</a> Genome Biology. 16, 191 (2015).</li><li>Hoon, M. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Putative+mammalian+taste+receptors:+a+class+of+taste-specific+GPCRs+with+distinct+topographic+selectivity.">Putative mammalian taste receptors: a class of taste-specific GPCRs with distinct topographic selectivity.</a> Cell. 96 (4), 541-551 (1999).</li><li>Laffitte, A., Neiers, F., Briand, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+roles+of+the+sweet+taste+receptor+in+oral+and+extraoral+tissues.">Functional roles of the sweet taste receptor in oral and extraoral tissues.</a> Current Opinion in Clinical Nutrition and Metabolic. 17 (4), 379-385 (2014).</li><li>An, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tas2r+activation+promotes+airway+smooth+muscle+relaxation+despite+beta2-adrenergic+receptor+tachyphylaxis.">Tas2r activation promotes airway smooth muscle relaxation despite beta2-adrenergic receptor tachyphylaxis.</a> American Journal of Physiology-Lung Cellular and Molecular. , (2012).</li><li>Fox, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relationship+between+chemical+composition+and+taste.">The relationship between chemical composition and taste.</a> Science. 74, 607 (1931).</li><li>Fox, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relationship+between+chemical+constitution+and+taste.">The relationship between chemical constitution and taste.</a> Proceedings of the National Academy of Sciences USA. 18, 115-120 (1932).</li><li>Bufe, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+molecular+basis+of+individual+differences+in+phenylthiocarbamide+and+propylthiouracil+bitterness+perception.">The molecular basis of individual differences in phenylthiocarbamide and propylthiouracil bitterness perception.</a> Current Biol.ogy. 15 (4), 322-327 (2005).</li><li>Reed, D. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+perception+of+quinine+taste+intensity+is+associated+with+common+genetic+variants+in+a+bitter+receptor+cluster+on+chromosome+12.">The perception of quinine taste intensity is associated with common genetic variants in a bitter receptor cluster on chromosome 12.</a> Human Molecular Genetics. 19 (21), 4278-4285 (2010).</li><li>Bobowski, N., Reed, D. R., Mennella, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Variation+in+the+TAS2R31+bitter+taste+receptor+gene+relates+to+liking+for+the+nonnutritive+sweetener+Acesulfame-K+among+children+and+adults.">Variation in the TAS2R31 bitter taste receptor gene relates to liking for the nonnutritive sweetener Acesulfame-K among children and adults.</a> Science Reports. 6, 39135 (2016).</li><li>Allen, A. L., McGeary, J. E., Knopik, V. S., Hayes, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bitterness+of+the+non-nutritive+sweetener+acesulfame+potassium+varies+with+polymorphisms+in+TAS2R9+and+TAS2R31.">Bitterness of the non-nutritive sweetener acesulfame potassium varies with polymorphisms in TAS2R9 and TAS2R31.</a> Chemical Senses. 38 (5), 379-389 (2013).</li><li>Roudnitzky, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genomic,+genetic,+and+functional+dissection+of+bitter+taste+responses+to+artificial+sweeteners.">Genomic, genetic, and functional dissection of bitter taste responses to artificial sweeteners.</a> Human Molecular Genetics. 20 (17), 3437-3449 (2011).</li><li>Guo, S. W., Reed, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+genetics+of+phenylthiocarbamide+perception.">The genetics of phenylthiocarbamide perception.</a> Annals in Human Biology. 28 (2), 111-142 (2001).</li><li>Bartoshuk, L. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Labeled+scales+(e.g.,+category,+Likert,+VAS)+and+invalid+across-group+comparisons:+what+we+have+learned+from+genetic+variation+in+taste.">Labeled scales (e.g., category, Likert, VAS) and invalid across-group comparisons: what we have learned from genetic variation in taste.</a> Food Quality Prefererences. 14 (2), 125-138 (2003).</li></ol>

The significance of this method is that it uses a multidisciplinary approach with features from medicine (the oral exam), experimental psychology (the taste test) and genetics (a validation step). Taste information is likely to develop as a diagnostic and prognostic tool because taste provides a window into the function of proteins elsewhere in the body. From an experimental psychology viewpoint, the addition of a simple exam can identify subjects who are not appropriate for the study of normative taste function. From a ...

Measures of human taste perception can be both part of medical care and a target of biomedical research, yet taste has received scant attention compared with hearing and vision (Table 1). From the medical perspective, when clinicians evaluate patients complaining of taste loss, in most cases the actual loss is of smell1, which has led to dismissal of taste loss as an uncommon and often invalid presenting complaint. Taste distortions (dysgeusia) are more common and frequently arise from the secondary effects of medications or peripheral nerve injury2,3, but neither form has an effective treatment (other than stopping the medication). Clinicians have also ignored taste loss because it has hitherto had little diagnostic or prognostic value on its own. However, although the measurement of taste has been a backwater, it may now be entering mainstream medicine with the revival of a historical appreciation that taste may be a diagnostic or prognostic tool4,5. For instance, bitterness perception can predict immune function6 or the willingness of a patient to take medication7. Nonetheless, biomedical researchers have largely neglected taste. This inattention may, in part, reflect the fact that early progress in understanding this sensory system has its roots in experimental psychology8, a field with which those in medicine may be relatively unfamiliar. Moreover, renewed interest in taste has ushered in standardized taste methods9 that build on earlier methods10, which while comprehensive are lengthy and inappropriate for clinical settings. Finally, confidence in taste measures can be weak because subjects report on their own experience and validation of their observations has hitherto been lacking. Our hope is that a simple measure that investigators or clinicians can easily administer will gain in popularity with both constituents. Here we describe a simple taste exam protocol that has three parts: an assessment of the oral cavity, the taste test, and a validation step using inborn genotype. First, we provide biological context for these procedures, which merge simple practices in medicine, sensory measures from experimental psychology and validation of responses using genotype and genetics.
Taste perception starts in the mouth, so an effective taste exam needs to include a brief clinical assessment for obvious oral diseases, redness, swelling and other discoloration. The oral cavity contains seven subsites: the tongue, gingiva, floor of mouth, buccal mucosa, labial mucosa, hard palate, and the retromolar trigone. Past studies of human taste focused on healthy participants or those with well-defined diseases, but as taste testing becomes routine in medical exams, it is important to record the condition of the oral cavity as part of the procedure.
The tongue itself is a muscular structure encased in mucosa; dotting its dorsal surface are papillae, the small raised structures that give the tongue its unique texture and contain taste receptor cells. We classify papillae by their shape: fungiform, filiform, foliate, and circumvallate. Fungiform papillae (FP) are located anterolaterally on the tongue and are round, with a mushroom shape11. Investigators have published several useful methods to quantify FP and we direct readers to these sources for measurement protocols12,13,14,15,16. Foliate papillae, shaped like the pages of a book (folia), are located exclusively on the lateral posterior tongue surface11. Circumvallate papillae, found in the sulcus terminalis of the tongue base, are large dome-shaped structures surrounded by mucosal walls (Latin circum, &#34;surround,&#34; + vallum, &#34;wall&#34;)11. The most numerous papillae, the filiform, are long and thin and do not contain taste receptors.
People differ in tongue anatomy. While the sources of this anatomic variation are unknown, it is determined in part by inborn genetic variation, with investigators reporting 31% concordance of tongue anatomy among dizygotic twins and 60% concordance among monozygotic twins17. Papillary density also differs among people, and although rare, at least one genetic disease (familial dysautonomia) results in a congenital absence of taste papillae18,19,20. Thus, before performing psychophysical testing, it is helpful to confirm the presence of FP as part of the brief assessment and note the relative size and color of the tongue and evidence of oral disease.
The taste papillae contain the sensory cells that when stimulated initiate taste sensation. Humans are capable of sensing at least five classes of taste: salty, sour, bitter, sweet, and umami. While salty, sweet, and umami tastes signal the presence of valuable food sources containing sodium chloride, glucose, and amino acids, respectively, bitterness and sourness signal the presence of potential toxins and acids from the bacterial decomposition of food, respectively, and induce aversive behavior21. Salty and sour tastes are transduced through the activation of ion channels found in some types of taste cells, though the understanding of salt transduction is evolving and it may require type I cells as well22,23. Bitter, sweet, and umami arise from activation of G-protein-coupled receptors on type II taste cells, each attuned to a particular taste. Heterodimers of subunits of three particular receptors transduce sweet and umami while bitter compounds activate a group of 25 different bitter receptors24. These bitter receptors can respond to multiple bitter compounds, and a single bitter compound often stimulates more than one receptor25. Despite the recent expansion of knowledge about the molecular basis of taste, novel pathways26 and new discoveries beyond the traditional five taste qualities (e.g., calcium27 or fatty acid28 perception) may lie ahead.
There are at least two surprising aspects of the taste families of receptors: genes that code for these receptors can differ markedly in DNA sequence and hence function among people, and many tissues of the body express these genes21,29,30,31. These extraoral sites include the brain, thyroid, upper and lower respiratory tract, and the gastrointestinal tract, among many others21,29,30,31. While the taste receptors at these locations do not participate in taste perception in the traditional sense, they likely sense the local chemical environment29,32. For example, the ciliated epithelium of the upper respiratory tract expresses the bitter receptor T2R38 (Bitter Taste Receptor 38), which responds to chemical compounds produced by bacteria and influences the innate immune response32, such as increasing mucociliary clearance and levels of anti-microbial peptides and nitric oxide. This finding has medical implications for chronic rhinosinusitis, a disease of chronic bacterial infection and inflammation of the upper respiratory tract and paranasal sinuses.
Of particular relevance to the taste exam we describe here is that the T2R38 bitter taste receptor, encoded by the TAS2R38 gene, exhibits genetic variability and therefore variable taste sensitivity. Perceptual differences for the bitter compound phenylthiocarbamide (PTC) were first described by the chemist Arthur Fox33; later this compound was identified as an agonist of the T2R38 receptor34. Individual differences arise from the DNA sequence of the TAS2R38 gene, which has three single-nucleotide polymorphisms, each yielding amino acid substitutions (A49P, A262V, and I296V; A: Alanine, P: Proline, V: Valine, I: Isoleucine). Two common haplotypes result, PAV and AVI, with PAV/PAV individuals being highly sensitive to PTC (&#34;tasters&#34;), AVI/AVI individuals being relatively insensitive (&#34;non-tasters&#34;), and heterozygous AVI/PAV individuals being more variable in their sensitivity35. There are more examples of genetic variation affecting bitter perception, e.g., taste receptor T2R19, encoded by the TAS2R19 gene, similarly exhibits genetic variability and differing taste sensitivity to the bitter compound quinine36. Likewise, variation in TAS2R31 affects the perceived bitterness of one of the high-potency sweeteners37,38,39.
Here we describe a rapid method to characterize a patient&#39;s sense of taste that draws on high-yield protocols in clinical medicine, experimental psychology and genetics.

<table border="0" cellpadding="0" cellspacing="0" width="850">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Disposable diagnostic penlight</td>
			<td style="width:163px;">Primacare</td>
			<td style="width:124px;">DL-9223</td>
			<td style="width:259px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">UltraLite Pro headlight</td>
			<td style="width:163px;">Integra LifeSciences</td>
			<td>AX2100BIF</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Millipore Q-Gard 2 water purification system</td>
			<td>EMB Millipore</td>
			<td style="width:124px;">QGARD00D2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Denatonium benzoate&#160;</td>
			<td>Sigma Aldrich</td>
			<td>D5765</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Phenylthiocarbamide</td>
			<td>Sigma Aldrich</td>
			<td>P7629</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Quinine hydrochloride dihydrate</td>
			<td>Sigma Aldrich</td>
			<td>Q1125</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Sodium Chloride</td>
			<td>Sigma Aldrich</td>
			<td>S1679</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Sucrose</td>
			<td>Sigma Aldrich</td>
			<td>S0389</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glass scintillation vials</td>
			<td>Thomas Scientific</td>
			<td>1230L59</td>
			<td>Same as Wheaton catalog no. 986580</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Oragene Discover OGR-500 DNA collection kit</td>
			<td>DNA Genotek</td>
			<td style="width:124px;">OGR-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">prepIT L2P Protocol reagents</td>
			<td>DNA Genotek</td>
			<td>PT-L2P-5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">rs713598 TaqMan SNP genotyping assay</td>
			<td>ThermoFisher Scientific</td>
			<td>C___8876467_10</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">rs1726866 TaqMan SNP genotyping assay</td>
			<td>ThermoFisher Scientific</td>
			<td>C___9506827_10</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">rs10246939 TaqMan SNP genotyping assay</td>
			<td>ThermoFisher Scientific</td>
			<td>C___9506826_10</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">rs10772420 TaqMan SNP genotyping assay</td>
			<td>ThermoFisher Scientific</td>
			<td>C___1317426_10</td>
			<td></td>
		</tr>
	</tbody>
</table>

taste exam: a brief and validated test

The emerging importance of taste in medicine and biomedical research, and new knowledge about its genetic underpinnings, has motivated us to supplement classic taste-testing methods in two ways. First, we explain how to do a brief assessment of the mouth, including the tongue, to ensure that taste papillae are present and to note evidence of relevant disease. Second, we draw on genetics to validate taste test data by comparing reports of perceived bitterness intensity and inborn receptor genotypes. Discordance between objective measures of genotype and subjective reports of taste experience can identify data collection errors, distracted subjects or those who have not understood or followed instructions. Our expectation is that fast and valid taste tests may persuade researchers and clinicians to assess taste regularly, making taste testing as common as testing for hearing and vision. Finally, because many tissues of the body express taste receptors, taste responses may provide a proxy for tissue sensitivity elsewhere in the body and, thereby, serve as a rapid, point-of-care test to guide diagnosis and a research tool to evaluate taste receptor protein function.

Results from the taste test have been pooled for all subjects evaluated (n = 840) and are presented after segregation by genotype. The full data set is accessible at https://carayata.shinyapps.io/TasteBoxplots/ and can be reviewed for each tastant assessed and for TAS2R38 and TAS2R19 genotypes. Results confirm the existence of perceptual taste differences for PTC among subjects grouped by TAS2R38 receptor genotype (Figure 3). Rating...

Watch this Scientific Journal Video about Taste Exam: A Brief and Validated Test at JoVE.com

Taste Exam: A Brief and Validated Test

This protocol measures human taste responses and includes a brief anatomical assessment, a short taste test, and a validation method using the subject&#39;s reported sensation and taste receptor genotype.

The emerging importance of taste in medicine and biomedical research, and new knowledge about its genetic underpinnings, has motivated us to supplement ...

Research

JoVE Journal

Medicine

Making Sense of Listening: The IMAP Test Battery

The ability to hear is only the first step towards making sense of the range of information contained in an auditory signal. Of equal importance are the ...

Technique to Collect Fungiform (Taste) Papillae from Human Tongue

Technique to Collect Fungiform Taste Papillae from Human Tongue

The sense of taste is critical for human life. It informs the body about the quality of food that will be potentially ingested and stimulates metabolic ...

The Trier Social Stress Test Protocol for Inducing Psychological Stress

This article demonstrates a psychological stress protocol for use in a laboratory setting.  Protocols that allow researchers to study the biological ...

The &alpha;-test: Rapid Cell-free CD4 Enumeration Using Whole Saliva

The ÃƒÅ½Ã‚Â±-test: Rapid Cell-free CD4 Enumeration Using Whole Saliva

There is an urgent need for affordable CD4 enumeration to monitor HIV disease. CD4 enumeration is out of reach in resource-limited regions due to the time ...

Flexible Colonoscopy in Mice to Evaluate the Severity of Colitis and Colorectal Tumors Using a Validated Endoscopic Scoring System

The use of modern endoscopy for research purposes has greatly facilitated our understanding of gastrointestinal pathologies. In particular, experimental ...

The Multiple Sclerosis Performance Test (MSPT): An iPad-Based Disability Assessment Tool

The Multiple Sclerosis Performance Test MSPT: An iPad-Based Disability Assessment Tool

Precise measurement of neurological and neuropsychological impairment and disability in multiple sclerosis is challenging. We report a new test, the ...

Determining The Electromyographic Fatigue Threshold Following a Single Visit Exercise Test

Theoretically, the electromyographic (EMG) fatigue threshold is the exercise intensity an individual can maintain indefinitely without the need to recruit ...

A Rat Carotid Balloon Injury Model to Test Anti-vascular Remodeling Therapeutics

The rat carotid balloon injury is a well-established surgical model that has been used to study arterial remodeling and vascular cell proliferation. It is ...

Ultrasound Assessment of Endothelial Function: A Technical Guideline of the Flow-mediated Dilation Test

Cardiovascular disease is the primary cause of mortality and a major cause of disability worldwide. The dysfunction of the vascular endothelium is a ...

A Blood-based Test for the Detection of ROS1 and RET Fusion Transcripts from Circulating Ribonucleic Acid Using Digital Polymerase Chain Reaction

We have developed novel methods for the isolation and characterization of tumor-derived circulating ribonucleic acid (cRNA) for blood-based liquid biopsy. ...