Salimetrics aims to introduce and explain common terms used in its kit inserts. This little glossary will help you to understand the principle behind the assays, support you with your experimental design and aid your analysis and interpretation of the results. Please get in touch if you think there are terms missing that you would like to have explained in more detail:
Just send an email with your suggestion and/or question to: [email protected]
17α Hydroxyprogesterone (17OHP): a steroid hormone produced in the adrenal glands and the gonads. 17OHP can be used as a marker to assess adrenal function.
Absorbance (or optical density): a measure of the transmission of an optical medium for a given wavelength. The higher the optical density, the lower the transmittance is. Most Salimetrics assays are read at 450nm.
Alpha Amylase: a digestive enzyme that breaks down dietary starch. Also a marker for the sympathetic nervous system.
Androstenedione: a steroid produced in the adrenal gland and gonads. It is a common precursor of male and female sex hormones and therefore a good marker for androgen synthesis.
Antibody: a protein produced by B cells as primary immune defence. The principle behind the ELISA technique is that antibodies capture antigens, which are the molecules of interest.
Assay Diluent: the assay diluent contains phosphate buffered saline, a pH indicator and preservatives. The pH indicator in the assay diluent alerts the user to samples with high or low pH values by turning the diluent either yellow (acidic) or purple (alkaline).
Blood contamination: samples visibly contaminated with blood should be recollected as they can interfere with the assay. Salimetrics recommend that samples be screened for possible blood contamination using a reliable screening tool such as the Salimetrics Blood Contamination kit.
Coefficient of Variation (CV%): is the percentage variation in mean; the standard deviation being considered as the total variation in the mean.
Competitive immunoassay: the antigen in the unknown saliva sample competes with labelled antigen to bind to the pre-coated antibodies. The amount of labelled antigen bound to the antibody site is then measured. The response is inversely proportional to the concentration of antigen in the unknown.
Controls: each kit contains vials of high and low levels of the molecule in interest in a saliva-like matrix to be used as control values. The control ranges established are to be used as a guide only and laboratories should establish its' own range.
Cortisol: is the major glucocorticoid produced in the adrenal cortex in a circadian rhythm. Levels of cortisol rise independently of this rhythm in response to stress.
Cotinine: is a metabolite of nicotine, found in tobacco. Cotinine is a reliable marker for the exposure to tobacco smoke.
C-Reactive Protein: is an acute-phase protein which is found increased in certain inflammatory disorders. CRP is widely used as a biomarker of inflammation in the body.
Cross reactivity: the possibility of an antibody raised against one antigen, also reacting against another, similar antigen, e.g. cortisol and dexamethasone.
Chromogenic Substrate: peptides that react with proteolytic enzymes under the formation of colour.
Dehydroepiandrosterone (DHEA): is an important endogenous steroid hormone which is co-released along with cortisol in response to ACTH from the pituitary gland.
Dehydroepiandrosterone-sulfate (DHEA(S): a steroid hormone produced primarily in the adrenal cortex. Unlike DHEA, DHEA-S does not normally exhibit any diurnal pattern of secretion.
Duplicate Analysis: saliva is assayed in two different wells on the microtiter plate, allowing a quality control check to ensure that the assay is giving the same reading in both wells. If the CV% is above 10%, the samples in question should be re-tested.
Enzyme: a type of protein which acts as a catalyst in specific biochemical reactions.
Enzyme-linked immunosorbent Assay (ELISA): is an immunological technique to detect and quantify the presence of a molecule based on antibody-antigen interactions.
Estradiol: a steroid hormone primarily produced by the ovarian follicles from testosterone. Research has focused predominantly on reproductive issues such as conception, ovulation, infertility and menopause.
Estriol: is a female sex steroid hormone largely associated with pregnancy and foetal development.
Estrone: a naturally occurring steroidal hormone. Research is often focused on pregnancy, reproduction and menopause.
Freeze Thaw Cycle: the process of freezing and thawing a sample. Multiple freeze-thaw cycles for saliva samples should be avoided as they can affect analyte concentration.
Horseradish Peroxidase: an enzyme used to label antigens and antibodies.
Inter-assay Precision: expression of the plate-to-plate consistency that is calculated from the mean values for the high and low controls on each plate.
Interleukin-1 Beta: a key pro-inflammatory cytokine that is released after infection, injury or antigenic challenge.
Interleukin-6: a pleiotropic cytokine involved in a multitude of inflammatory responses with roles in immune regulation and acute and chronic inflammatory diseases.
Intra-assay Precision: the average value calculated from individual CV’s for all duplicates, even if the total number of samples requires the use of multiple assay plates.
Kinetic Assay: the assay measures the enzymatic activity of a molecule, rather than the concentration. The increase in absorbance is directly proportional to the molecules enzymatic activity.
Linearity: the ability of an assay to return values that are directly proportional to the concentration of the target analyte in the sample.
Mean: average of all measurements belonging to one sample
Melatonin: a hormone derived from serotonin and secreted by the pineal gland. Melatonin helps to regulate the sleep-wake cycle.
Microtiter plate: is a flat plate with multiple wells used as individual test tubes.
Monoclonal antibody: monospecific antibodies which are made by identical immune cells that are all clones of a unique parent cell.
Nonspecific binding wells: are specific wells on a microtiter plate that do not have any antibody coated to it. They don’t have to be included in sample analysis, but provide a measure to assess analysis quality.
Optical density (or absorbance): a measure of the transmission of an optical medium for a given wavelength. The higher the optical density, the lower the transmittance is. Most Salimetrics assays are read at 450nm.
Passive Drool Collection: is a collection method where participants allow the saliva to pool in their mouths before transferring to a cryovial using straw-like collection materials. For detailed collection instructions, please have a look at our saliva collection booklet.
Plate Reader: are laboratory instruments designed to analyse biological and chemical substances in microtiter plates.
Polyclonal antibody: are a collection of immunoglobulin molecules reacting against a specific antigen, each identifying a different epitope
Progesterone: a steroid hormone playing a role in the female menstrual cycle, pregnancy and embryogenesis.
Recovery: a test used to determine whether analyte detection can be affected by the difference between diluent used for preparation and the experimental sample matrix.
Room Temperature: all Salimetrics assays have been validated at room temperature (20°C-23.3°C). It is important to bring all reagents to room temperature before starting the analysis.
Salimetrics Children Swab: is an inert polymer cylindrical swab with a volume capacity of 2ml. The children swab is longer than the oral swab and can be used for children from 6 months to 6 years. For detailed collection instructions, please have a look at our saliva collection booklet.
Salimetrics Infant Swab: is an inert polymer cylindrical swab with a volume capacity of 1ml. The infant swab is longer and thinner than the oral swab and can be used for children under 6 months. For detailed collection instructions, please have a look at our saliva collection booklet.
Salimetrics Oral Swab: is an inert polymer cylindrical swab with a volume capacity of 2ml. The oral swab can be used from children aged 6 and above. For detailed collection instructions, please have a look at our saliva collection booklet.
Salivary Flow rate: can affect the concentration of some of the analytes and has to be taken into account when testing for alpha-amylase, DHEA(S) and SIgA.
Secretory Immunoglobulin A: is the dominant immunoglobulin in external secretions that bathe mucosal surfaces and is often characterized as a component of the immune systems first line of defence against bacteria and microorganisms.
Sensitivity: the lower limit of sensitivity is determined by interpolating the mean optical density minus 2 standard deviations of a number of replicates at the zero concentration level.
Saliva-Serum Correlation: a measure of how well concentrations of certain analytes can be reflected in saliva when compared to serum.
Singlet: saliva is assayed in only one well on the microtiter plate, therefore no CV% can be established.
Standards: Different known concentrations of the analyte of interest in order to establish a standard curve which is used for calculating analyte concentrations in the unknown samples.
Standard Deviation: indicates how much variation from the average exists.
Substrate: a substance on which an enzyme acts.
Sulphuric Acid: a highly corrosive acid used to stop the enzymatic reaction before measuring the absorbance.
Swab Collection: a form of saliva collection using a swab consisting of inert polymer material. Salimetrics offers infant, children and oral swabs. For more information visit: www.salimetrics.com/collection-supplies
Testosterone: is an anabolic steroid hormone synthesized from Androstenedione in the Leydig cells of the testes of males and, in smaller quantities, in the ovaries of females.
Tetramethylbenzidine (TMB): a chromogenic substrate used as visualising reagent in ELISA’s.
Transferrins: are iron-binding blood plasma glycoproteins which can be used to detect blood contamination in saliva samples.
Unknown Samples (Unk): a term used for a saliva sample with unknown concentration of the analyte of interest.
Wash Buffer: consists usually of phosphate buffered saline containing detergents and preservatives and is used to wash any unbound antibodies from the microtiter plate.
Zero Wells: also known as blank wells; have antibody for the specific antigen coated to them, but only assay diluent will be added and therefore serve as zero values.
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