Quantitative sensory testing

Currently, treatment of DSP and ATN is similar to many other neuropathies that have predominantly painful sensory involvement (Mendell and Sahenk 2003 Gonzalez-Duarte et al. 2007). It is purely symptomatic as there are no proven regenerative therapies to reverse the underlying process. An 8-month prospective pilot study reported an improvement in subjective quantitative sensory testing (QST) in HIV-infected patients who responded to HAART (Martin et al. 2000). The patients who did not respond to HAART did not show any improvements in QST. It is possible that suppression of viral load will slow the progression of DSP. Some studies have found a correlation between viral load and incidence (Childs et al. 1999), or severity (Simpson et al. 2002) of sensory neuropathy. Others, however, did not find any correlation between plasma viral loads and incidence of DSP or ATN (Brew et al. 2003). 

Industry has standardized procedures for the quantitative sensory assessment of the perceived olfactory intensity of indoor malodors and their relationship to the deodorant efficacy of air freshener products. Synthetic malodors are used for these evaluation purposes. These malodors should be hedonicaHy associated to the "real" malodor, and must be readily available and of consistent odor quaUty. These malodors should be tested in various concentrations and be representative of intensities experienced under normal domestic conditions. 

An extensive list of volatile compounds in apples and other fruits was included in a review by Nursten (222). White (223) reported that the principal components of the aroma of apples were alcohols (92% ) methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-l-propa-nol, 2-methyl-l-butanol, and 1-hexanol. The other constituents included 6% carbonyl compounds and 2% esters. Later, MacGregor et al. (224) tentatively identified 30 volatile components of McIntosh apple juice including four aldehydes, one ketone, 11 alcohols, 10 esters, and four fatty acids. The major organic volatiles in several different extractants of Delicious apple essence were identified and quantitatively estimated by Schultz et al. (225). They reported from sensory tests that low molecular weight alcohols contributed little to apple aroma. Flath et al. (226) identified... 

List of Abbreviations HSAN, Hereditary sensory and autonomic neuropathies HSN, Hereditary sensory neuropathies NCS, Nerve conduction studies QST, Quantitative somatosensory testing... 

Quantitative somatosensory testing (QST) uses calibrated tools to assess the function of all the sensory modalities. The smaller caliber nerves are evaluated by measuring pain and temperature (hot and cold) thresholds, and larger caliber nerves are evaluated by measuring the thresholds for perception of vibration, joint position, and touch. This is done by touching the patients skin with stimuli of defined characteristics, such as a computer-controlled probe that can heat or cool to specific temperatures. The effectiveness of QST is limited because it requires subject cooperation and is inherently subjective, as it relies on the reported interpretation of sensory stimulation from the subject. This also influences reproducibility of this sensory test (Fink and Qaklander, 2006). 

Two types of sensory assessment are used for ice cream, analytical methods, in which trained tasters provide quantitative sensory data, and consumer testing, in which consumers are asked questions such as how much they like a product and whether they would be likely to buy it. 

The analytical sensory tests are confined to sensitivity, discriminatory, quantitative (intensity), and descriptive or qualitative analysis of the sensory attributes of food. 

UV-Vis may be used in the QA laboratory to either determine the concentration of a particular component in an incoming ingredient (quantitative analysis) or to obtain an overall spectrum (scan from 200-700 nm). An overall spectrum has value in providing a profile for future reference of either new batches of an incoming ingredient or a newly made finished flavor. These determinations are often made on dilutions that are used for sensory testing and require only 30 sec to obtain. 

Discriminant Sensory Analysis. Discriminant sensory analysis, ie, difference testing, is used to determine if a difference can be detected in the flavor of two or more samples by a panel of subjects. These differences may be quantitative, ie, a magnitude can be assigned to the differences but the nature of the difference is not revealed. These procedures yield much less information about the flavor of a food than descriptive analyses, yet are extremely useful eg, a manufacturer might want to substitute one component of a food product with another safer or less expensive one without changing the flavor in any way. Several formulations can be attempted until one is found with flavor characteristics that caimot be discriminated from the original or standard sample. 

Many tests have been devised to provide quantitative measures of behavioral disturbances caused by neurotoxic chemicals. Tests have been devised that assess the effects of chemicals on four behavioral functions (D Mello 1992). These are sensory, cognitive, motor, and affective functions. However, because the entire nervous system tends to work in an integrated way, these functions are not easily separable from one another. For example, the outcome of tests focused on sensory perception by rats may be influenced by effects of the test chemical on motor function. 

The primary products from autoxidation are hydroperoxides, which are often simply referred to as peroxides. Peroxides are odorless and colorless, but are labile species that can undergo both enzymatic and nonenzymatic degradation to produce a complex array of secondary products such as aliphatic aldehydes, alcohols, ketones, and hydrocarbons. Many of these secondary oxidation products are odiferous and impart detrimental sensory attributes to the food product in question. Being able to monitor and semi-quantitate the development of peroxides by objective means (e.g., PV determination) over time is important for food scientists who want to characterize the quality of an oil or a lipid-containing food product, even though the peroxides themselves are not directly related to the actual sensory quality of the product tested. 

We have seen that in the short term, the changes in skin due to cleansing primarily manifest as changes in sensory perception. Consumer perception methods are the primary means of assessing the transient onset of tightness and itch. Naive panels can provide comparative data among several cleansers tested but can not provide consistent quantitative measure of performance. Expert panels... 

The vibration sensation test is purported to be a quantitative measure of perception of a vibrating stimulus. It is used to see if a person can volitionally tell the examiner when a stimulus is first perceived. It is intended to reveal impairment in the ability of a peripheral nerve to conduct an impulse. If the subject has a high threshold for this test, it is suggested by the amount of time the subject requires for acknowledging his/her perception of the stimulus. This testis subject to embellishment by the examinee and to observer bias by the test administrator. Such impairments detected on screening tests such as this must be correlated with other more objective tests for evidence of peripheral neuropathy such as nerve conduction velocities, tendon reflex responses, and patterns of sensory loss detected by pin prick perception. 

In evaluating gel structure, fundamental characteristics such as brittleness, hardness, and elasticity can be quantitatively measured and related to sensory attributes such as chewiness and gumminess. Sherman (56) found sample dimension and cross head speed affect these readings. Gels were not linear In their force-compression behavior. Slow cross head speeds can lead to stress relaxation, so from low compression test rates. It was Impossible to predict how a gel would behave at high compression rates as In the mouth. 

---