Glossary of Laboratory Diagnostic Terms

Accuracy

Agreement between your test result value and the true value; i.e. how correct your result is.

Affinity

An attractive force between substances or particles that causes them to enter into and remain in chemical combination, for example; the binding of antibody to antigen.

Aggregation

The grouping of units or parts into a mass or whole.

Aliquot

The division of a sample into at least two smaller size vials.

Amplification

Amplification generally means an addition to or expansion of a statement or idea. In medical terminology, amplification refers to the selective copying of a gene or any sequence of DNA. This occurs naturally in the body in order to satisfy the increased requirement of individual cells for gene products such as proteins. Amplification also plays a role in cancer cells when a tumour cell copies DNA segments as a result of cell signals or external environmental factors. Artificial amplification is conducted due to its central role in gene research.

Analyte

The chemical substance being measured in an assay, usually contained in blood or other body fluids.

Anabolic Steroid

Anabolic steroids are a group of synthetic steroid hormones that promote tissue growth and the storage of protein, as such they are sometimes used in food producing animals to increase the lean meat to fat ratio.

Antibody

A protein produced by our body in response to an antigen. There are 5 classes of antibodies (IgG, IgM, IgE, IgA, IgD). The antibody binds to and neutralises the antigen.

Anticoagulant

A substance that stops the blood from clotting.

Antigen

Antigens are usually foreign substances which enter the body and trigger the immune system to produce antibodies in order to fight off the potential infection. Antigens can be toxins, foreign blood cells, bacteria or the cells of transplanted organs.

Antimicrobial

The term given to a group of drugs that inhibits the growth or destroys microorganisms.

Antioxidant

A molecule that protects cells from oxidative damage of oxygen and free radical molecules that are chemically unstable and cause random reactions damaging proteins nucleic acids and cell membranes.

Antiserum

A solution of antibody or mixture of antibodies either purified or un-purified used in the manufacture of diagnostic reagents or used as a component of a diagnostic kit.

Assay

A diagnostic test to measure the concentration or level of a particular analyte.

Assayed

Assayed controls are used for the control of accuracy and reproducibility of results. Each parameter has an assigned mean +/- 2SD range generated from up to 3000 independent laboratories world-wide and approximately 98,000 results.

Assay Range

The assay range describes the highest and lowest concentrations, at which a reaction is still measurable.

Aspiration

The withdrawal of fluid or tissue, e.g. by a wash probe on an analyser.

Aqueous

The term aqueous simply means dissolved in water.

Avidity

The average affinity of a mixture of antibody to their corresponding antigen.

B

Benchtop

This term simply refers to a position of an object, i.e. ‘on top of a bench’. However, in a scientific setting, it is used to describe an analyser which is small enough to fit on top of a laboratory workbench but is too large to be a point of care system.

Bias

The term bias refers to the difference between the expected result and an accepted reference value.

Biochemistry

Biochemistry is the study of the chemical structures and vital processes which occur in living organisms. Biochemists study the compounds in the body and how these result in chemical processes. They seek to understand such processes both within healthy and unhealthy organisms.

Biochip

Proprietary solid substrate onto which reactive species are prefabricated for the detection of specific analytes.

Biological Variation

The mean for each laboratory’s results will not be exactly the same. Individual homeostatic setting points usually vary. This difference is known as biological variation.

Biotechnology

As the name suggests, this field of study is a combination of biology and technology. It is primarily concerned with the technical exploitation of biological processes. Through microbiological or biochemical techniques, cell cultures, microorganisms or enzymes are used to activate targeted metabolic processes. Used in conjunction with genetic engineering, biotechnology can be used to program certain microorganisms to perform specific tasks.

Blood Clotting

Blood clotting, also known as coagulation performs the vital task of preventing excessive blood loss in the event of injury. Leakage of blood is prevented by the blood cells sticking to the wound. However, clotting can sometimes fail to occur, this is known as haemophilia.

Blood Gas Analysis

The body has many functions, one critical function is to transport substances such as oxygen, carbon dioxide, nutrients and excretions. Most of these substances are gases; therefore blood gas analysis determines their concentrations in arterial and venous blood.

Blood Screening

Blood screening is used to detect pathogens which cause symptomless diseases. An effective diagnosis then allows correct treatment to begin in good time, thus improving the patient outcome. Blood screening is also performed on donated blood to identify and remove any infected blood.

Bovine

Bovine controls are prepared from certified disease-free animal source material and offer high performance when cost considerations are paramount.

Buffer

A liquid solution containing a combination of chemicals, which control and maintain the pH of any other solution it is added to.

C

Calibration

The process of setting up or standardising an assay using a calibrator or standard of known concentration.  When the data generated is analysed this can then be used to calculate results for any subsequent sample of unknown concentration.  It adjusts the accuracy of an assay method.

Calibrator

A material, generally serum based with an accurately assigned analytical value, used to calibrate diagnostic assays.

Cancer

There are many different types of cancer, some, such as skin cancer, are more common than others. Cancer is an abnormal growth of cells which grow and can spread to other parts of the body. The type of cancer is named after the organ it originated in, for example if it began in the lungs, it is lung cancer. Although cancer is a leading cause of death, not all cancers are terminal; skin cancer for example is often curable.

Cardiology

Cardiology is essentially the study, diagnosis and treatment of heart disorders. Cardiac related conditions are a leading cause of death in the industrialised world, therefore the area of cardiology is a primary research area within medicine.

Centrifugation

Centrifugation is a process used to separate or concentrate materials suspended in a liquid medium by use of the centrifugal force.

Chemiluminescence

The process in which energy from a chemical reaction is released directly as light.

Cholesterol

Cholesterol has somewhat of a bad reputation as it is generally viewed as harmful to the heart. However, cholesterol is a very important and essential part of our diet. Cholesterol is needed for the formation of bile acids, vitamin D, progesterone and much more. LDL is known as the bad cholesterol as it is associated with increased risk of coronary heart disease. HDL is therefore the good cholesterol as elevated HDL levels are associated with decreased risk of coronary heart disease.

Chromagen

A substrate which reacts with an enzyme or directly with the analyte to produce a coloured end-point which can subsequently be measured to quantify the concentration of the analyte.

Chromosome

A chromosome is the carrier of genetic information that is inherited from generation to generation. They exist in every cell nucleus. Cells in humans contain a double set of chromosomes, a total of 23 pairs of chromosomes exist in each human.

Clinical Chemistry

This field deals with analysing blood, urine and other body fluids. Their constituents i.e. proteins and enzymes are determined. The results from this analysis is used as a basis for patient diagnosis.

Coefficient of variation (CV)

The coefficient of variation (CV) is the relative standard deviation i.e. the SD expressed as a percentage of the mean. The CV reflects a ratio of the standard deviation to the concentration level, and therefore provides a better estimate of method performance over a range of concentrations.

Coefficient of variation Index (CVI)

CVI is an indicator of your precision and is calculated by dividing your CV% by the peer group %CV. The ideal CVI is <1, which is obtained when your %CV is less then that of the peer group.

CVI = CV / Peer Group CV

Co-enzyme

A small but complex biochemical which many enzymes require to be able to carry out their function. Examples are NADH, NAD+ and ATP. Many vitamins are co-enzymes.

Colorimetric methods

Colorimetric methods result in a coloured end product, the intensity of which is directly proportional to the concentration of the analyte being measured at 400-700nm.

Conjugate

This contains the various enzyme labelled analytes or enzyme labelled detection antibodies utilised in an immunoassay to generate a measurable signal.

Consolidation

Extensive analyte menus allow significant consolidation of existing controls.  An average laboratory may rationalise from 7 different control products to a single control product.

Control

A serum based material with assigned target values and acceptable ranges to evaluate the accuracy and reproducibility of a diagnostic assay.

Correlation

A clear positive relation between two methods.

Cross Reactivity

When an antibody binds or reacts with proteins other than the one it is specific for.

CSF

Cerebrospinal fluid.  CSF controls are available ensuring the same matrix as the patient sample.

Custom Made

A custom made quality control is manufactured to meet a customers own specifications.  Custom made sera may involve the addition of extra analytes, removal of unwanted analytes, alteration of analyte levels or alteration of vial size.

Cuvette

A reaction vessel (similar to a tube) used in photometric analysers.

Cytopathology

Also histopathology; the study of tissue samples of patients to detect diseases.

D

Dedicated reagent

A reagent packed and bar-coded for specific use on one analyser.

DGKC

Deutsche Gesellschaft für Klinische Chemie

Diabetes Mellitus

Diabetes is a metabolic condition characterised by high blood sugar levels which result from defects in insulin production. Blood sugar levels are controlled by the hormone; insulin. Blood sugar levels rise after eating, insulin is then released to normalise the level. However, in diabetes patients, insufficient amounts of insulin is produced causing hyperglycemia. Diabetes is a chronic condition which can lead to kidney failure, blindness, stroke and cardiovascular disease.

There are two types of diabetes, Type 1 and Type 2:

Type 1: Develops when the insulin producing cells have been destroyed, meaning the body is unable to produce any insulin. Glucose then builds up in the blood. Type 1 can occur at any age, though usually appears before the age of 40.

Type 2: Occurs when the body can produce insulin but not enough of it or else the insulin that is produced does not function correctly. Glucose then builds up in the blood. Type 2 usually develops in people aged over 40, although is now becoming more common in children, adolescents and young people.

Diagnostic Kit

A combination of reagents liquid or freeze-dried which can be used in a laboratory to measure specific serum or urine parameters to diagnose and monitor the therapy of specific diseases.

Disease Marker

A disease marker is any serum component which rises or falls outside its normal range in response to disease.

DNA

Deoxyribonucleic acid. DNA is one of two types of molecules which encode genetic information, the other being RNA. DNA is the genetic material in humans and RNA is transcribed from it. DNA forms a double stranded molecule held together between the base pairs of nucleotides. This molecule forms a double helix. There are four nucleotides in DNA, each containing a base; adenine (A), guanine (G), cytosine (C) or thymine (T).

Drug Residue

The small amount of drug left behind in animal products after treatment. Includes any degradation products which are a direct result of the drugs metabolism.

E

ECCLs

The European Committee for Clinical Laboratory Standards

ELISA

Enzyme Linked Immunosorbent Assay.  A sample containing an unknown amount of antigen is immobilised on the surface of a micro titre plate.  An enzyme labelled antibody specific to the antigen of interest is added and forms a complex with the antigen, a series of washes are then carried out to remove any proteins or antibodies that are not specifically bound.  Finally the substrate is added and converted to visible signal which corresponds directly to the quantity of antigen in the sample.

End-Point

In an end-point reaction the reaction is allowed to go to completion. One final absorbance is measured which will relate directly to the analyte concentration in the sample.

Endocrinology

This is the study of hormones, their receptors, the signalling pathways they create and the conditions associated with them. Hormones under study within endocrinology include the thyroid hormones. Endocrinology is often studied along with diabetes and metabolism.

Enzymatic

Enzymatic methods have gradually replaced classical chemical methods.  They provide the laboratory with greater specificity and greater accuracy.

Enzyme

Complex proteins that are produced by living cells and catalyze specific biochemical reactions.

Epitope

The part of the antigen (on its surface) that can be recognised by the antibody.

E-Transfer

The RIQAS E-transfer software enables fast data transfer and allows participants to view and store reports electronically dramatically reducing turnaround time.

External Quality Assessment (EQA)

The term EQA refers to the comparison of performance to other laboratories.  A system of objectively checking laboratory results by means of assessment by an external agency.

F

Freeze Drying

Also called lyophilisation, is a process in which an unstable mixture of chemicals can be stabilised by removing water and then sealed under a vacuum in a glass vial.

Fragmentation

When something is broken up, the resulting smaller parts are called fragments. Fragmentation occurs during a PCR (polymerase chain reaction) and can be conducted by heating of chromosomes or parts of the DNA.

Fully Automated

With a fully automated system all assay steps are performed automatically, the operator is only required to load reagents/samples and to programme the instrument.

G

GC-MS

Gas Chromatography-Mass Spectrophotometry.  A technique that combines gas liquid chromatography and mass spectrophotometry to identify different substances or components within a test sample.

Gene

A gene is the basic biological unit of heredity or genetic features. Genes are essentially the building blocks which allow proteins to control the diversity of processes within each human body, such as fighting infections.

Gene expression

Gene expression is the translation of the information encoded in a gene into another form, i.e. protein or RNA, this translation process is known as transcription.

Genetics

Genetics is the study of heredity, for example the passing of characteristics such as eye colour and even the transmission of genetic diseases. This enables scientists to further understand such diseases and therefore potentially improve diagnostic and treatment options. There are many different types of genetics including classical genetics, clinical genetics, forensic genetics and pharmacogenetics.

Genomics

Genomics is the study of genes and their functions. It is interested in the structure of the genome, which carries all the genetic material, like a blueprint. Genomics studies how molecular mechanisms and genetic factors affect disease.

Glucose

Glucose, or dextrose, as it also known, is the main sugar produced by the body and is the primary source of energy. Glucose is made from fats, proteins and carbohydrates and is transported via the bloodstream to individual cells. Cells then require insulin to be able to use the glucose effectively.

Growth Promoter

The term growth promoter is used to describe a class of drugs that have growth promoting properties.  They are often used to improve the ability of food producing animals to efficiently and effectively use nutrients in order to produce leaner, more affordable meat.

H

Haematology

The study of blood and its components. Blood is an important transport mechanism for essential nutrients. Haematology studies disorders associated with blood such as coagulation.

Haemoglobin

The protein in the centre of a red blood cell (erythrocyte), that is responsible for binding and delivering oxygen to the body. It also gives blood its red colour.

Haemolysis

Lysis of red blood cells with liberation of haemoglobin; a haemolysed sample is red.

Half-life

The time required to break down and eliminate half the concentration of a substance. At half the concentration a drug stops being effective, so the half-life indicates the amount of time that a drug will be effective.

Hapten

A foreign molecule that is too small to be recognised as an antigen by the human body.

Harvesting

To remove or extract, (as living cells, tissues or organs) from a living being or a culture.

Histogram

Compares the distribution of your instrument group, method group and all method group

Histopathology

Also Cytopathology; the study of tissue samples of patients to detect diseases.

HPLC

High Performance Liquid Chromatography is a method used in clinical chemistry to separate a mixture of compounds and identify the individual components.

100% Human

Fully human controls are preferred for immunological methods including those for serum proteins and hormones. Fully human controls are donor tested at source and found to be non-reactive for Hepatitis B and C antigen and HIV I and II antibodies. Human serum offers a matrix consistent with human patient samples. 

Human-based

Human based controls are donor tested at source and found to be non-reactive for Hepatitis B and C antigen and HIV I and II antibodies. Human serum offers a matrix consistent with human patient samples.

Hybrid

A specially cultivated cell which contains components from one or more genomes.

Hybridoma

A hybrid cell produced by the fusion of an antibody-producing lymphocyte with a tumour cell and used to culture continuously a specific monoclonal antibody.

I

IFCC

The International Federation of Clinical Chemistry

Immunoaffinity Columns

Used to clean up samples for analysis by HPLC or ELISA.  They work by binding and removing the target analyte from a variety of different sample types.

Immunoassay

An assay that makes use of the affinity of an antibody to a particular antigen. Specific antigens and antibodies in the body can be indicators of specific diseases or disorders. An immunoassay test gathers information on the quantity of these antigens and antibodies.

Immunochemistry

A part of immunology, immunochemistry looks into the chemical detection of immune reactions.

Immunology

The study of all aspects of the immune system and its components, including disorders.

Immunoturbidimetry

A method of measuring turbidity that is created during a chemical reaction between antigen and antibody.

Inert

Inert means chemically non-reactive.

Independent Advisory Panel

RIQAS participants have access to an independent advisory panel consisting of scientific and clinical experts. This ensures professional and ethical conduct of the scheme and participant confidentiality.

Insulin

Insulin is a hormone produced naturally by the pancreas and it controls the levels of glucose in the blood. Insulin enables glucose to be used as energy by the body. The body can fail to make or effectively produce insulin which results in Diabetes Mellitus. Diabetes is treated with insulin to reduce the levels of glucose in the blood.

Interferent

A substance that interferes in any way with a chemical reaction and gives false results.

Internal Quality Control (IQC)

The term IQC refers to the daily monitoring of quality control sera.  Internal quality control procedures have an immediate effect on the laboratory’s activities and should actually control, as opposed to merely examining the laboratory’s output.

In Vitro

A procedure carried out outside a living organism.

In Vivo

A procedure carried out within a living organism.

ISE

Ion Selective Electrode

K

Kinetic

A diagnostic test where the speed of the reaction is measured and the rate at which the signal is produced will reflect the analyte concentration.

L

Latex Slide Test

Latex slide tests are simple manual tests performed on a disposable card or glass slide.

LC-MS

Liquid Chromatography – Mass Spectrophotometry

Levey-Jennings

Compares individual performance to the distribution of peer group results

Life Sciences

Life Sciences cover a wide base of important medically relevant areas. Life Sciences include all fields which are concerned with the study of living organisms, such as plants, animals and humans. Industries concerned with Life Science research include veterinary diagnostics, pharmaceutical research and biotechnology.

Ligation

The binding together of two substances.

Limit of Detection (LOD)

The LOD refers to the smallest quantity of analyte that can be detected and distinguished from the blank with a reasonable degree of certainty.

Linearity

In chemical terms; expression of the proportional relationship between response and concentration over a defined range.  It is used to describe the highest concentration, at which a reaction is still measurable.

Lipid

A lipid is a water insoluble substance and is the name of a large class of structurally and functionally diverse molecules.  Important lipids include fatty acids.

Liquid Stable

Liquid ready to use controls stable at 2-8oC therefore no need to defrost before use.

Lyophilised

The term lyophilised refers to a material that has been freeze-dried.  Freeze-drying is a process by which an unstable mixture of chemicals can be stabilised by removing water and then sealed under a vacuum in a glass vial.

Lysis

A process of disintegration or dissolution of cells. For example, haemolysis is the dissolution of red blood cells.

M

Manual

In manual tests the functional steps are carried out by hand and the reactions measured using a spectrophotometer.  Results are not produced directly and the operator will generally have to perform calculations or plot a graph to generate meaningful data.

Maximum Residue Limits (MRL)

The maximum residue limit refers to the maximum permissible level according to legislation of a chemical or group of chemicals in human or animal feed.

Mean

The arithmetic mean is calculated by dividing the sum of all results by the number of results.  Your mean is presented as monthly or cumulative.  The mean for comparison is used to calculate performance statistics depending on the peer group you have chosen.

Metabolism

The general term given to describe the body’s chemistry and all its biochemical reactions and transformations. It refers more specifically to the body’s ability to turn food into energy.

Metabolite

Any biochemical compound which plays a key role in the metabolism of the body.

Microbiology

The study of microorganisms, such as bacteria, viruses and parasites.

Microarray

Microarrays consist of many probes attached chemically to a substrate with a very small surface. This surface could be a glass slide or a microchip. Each probe, which holds genetic information, can detect many different genes at the same time. Microarrays can be used to assist in the detection of genetic variations.

Monoclonal

Cells derived from a single origin.

Molecule

A molecule is the smallest possible unit in a chemical compound. It is made up of at least two atoms held together by bonding forces. H2O is an example of a molecule.

Molecular Biology

Molecular Biology is the study of biology on a molecular level. It examines the structure and function of biologically important molecules within an organism in order to study viruses. It also encompasses biochemistry and genetics.

Mutation

In a strict sense, mutations are changes in genes caused by genetic recombination. A change in the base sequence of DNA for example, represents to a mutational change. It is a permanent structural change in the DNA. Some mutations can be harmless and have no effect whilst others can be harmful. Mutations can be inherited.

Myocardial Infarction (MI)

This is a heart attack. A heart attack occurs when a coronary artery is suddenly blocked by a blood clot. This causes the death of heart muscle. This blockage deprives the heart of blood and oxygen, therefore causing serious injury to the heart which causes pain in the chest. The damage can be irreversible if the blood flow is not started again quickly.

N

Near patient testing

This term is used to describe a rapid diagnostic test or testing platform which allows clinicians to respond quickly to critical situations. Near patient testing can be performed in a doctor’s office, in the emergency room or other near patient sites. It enables the clinician to decide on diagnosis and potential treatment at the site of testing, for a rapid diagnosis thus improving patient outcome.

Normal Range

The normal range refers to the results expected from a healthy individual.  It is important to note that results may vary with age, gender and geographical location.

O

OEM

Other Equipment Manufacturer: Products manufactured by a supplier which is then sold under another company’s name.

Oncology

This field of medicine examines tumours and cancerous conditions and the subsequent treatment options as well as diagnosis.

P

Parameter

Another term often used to describe the analyte being tested in an assay.

Pathogen

A specific causative agent of disease such as bacterium, virus or chemical etc.

Pathological

The concentration of some analytes within the body are altered or caused by disease. Pathological control contains abnormal levels of analytes associated with disease.

Peer Group

A peer group consists of a number of laboratories using the same quality controls,  methodology, instrument and reagents as such a peer group can be described as the ideal consensus group.

Percentage Deviation (% Deviation)

Your % deviation from the mean for comparison.

% Deviation = Result – MFC x 100% / MFC

PDF Reporting

RIQAS reports can be presented in PDF offering easy review and storage of your laboratory’s EQA data.

pH

This is a measure of the acidity or alkalinity of a solution. The activity of all biochemical reactions is influenced by the pH of its surroundings.

Photometry

Photometry describes the measurement of visible light.

Plasma

The clear amber liquid which is derived from whole blood that has been collected in the presence of an anticoagulant in such a way as to prevent clot formation.  Plasma differs from serum in that it contains all the clotting factors and fibrinogen which are lost on clot formation.

Point of Care (POC)

The term used for diagnostic testing which takes place at or near the patient’s site of care.

Polyclonal Antibody

A mixture of different antibodies detecting different epitopes on the surface of the same antigen.

Precision

Precision refers to the reproducibility of test results and is a measure of how disperse the values are.  Inter-assay and Intra-assay are two distinct measures of this.

Proliferate

To grow by rapid production of new cells.

Protein

A protein is a molecule composed of one or more chains of amino acids. Proteins are needed for the function of cells, tissues and organs. They are also essential for muscle, skin and bones.

Purify

The removal of unwanted contaminates or cleaning of a protein or chemical so it can be used in a particular application without interference.

Q

Quality Assurance

The term given to the systems established within a manufacturing process or operational system to ensure and maintain the quality and consistency of the final product.

Quality Control

The process of detecting errors in any manufacturing or operational system. In the case of diagnostic testing it refers to the accuracy and reliability of the diagnostic result generated.

R

Reagent

A component of a kit used to carry out a chemical reaction to determine levels of different analytes.

Random Access

Random access refers to the capability of an analyser to perform any requested test in any sequence.

Recombinant Protein

A protein created by artificially inducing a DNA sequence into a living cell.

Reconstitution

The addition of water to a freeze-dried reagent or control material to return it to its former condition.

Reference Method

Reference methods are generally considered the most accurate for the determination of a specific analyte and are traceable to international standards, enabling inter-laboratory standardisation.

RIQASNet

RIQASNet is an internet-based data entry system allowing participants to return results and view reports online.  RIQASNet enables direct access for the submission of results and retrieval of RIQAS reports.  Participants can submit current, corrected, late and future results, directly into RIQAS database eliminating need to fax or email EQA results.

RNA

RNA is short for ribonucleic acid. This is a nucleic acid molecule which is similar to DNA but contains ribose rather than deoxyribose. Several classes of RNA exist and all have a key role in protein synthesis. Transfer RNA (tRNA) carries amino acids leading to the formation of protein with a specific amino acid arrangement. Messenger RNA (mRNA) carries the message of the DNA to cells where protein is made. Ribosomal RNA (rRNA) is a component of ribosomes and it functions as a nonspecific site for making polypeptides.

S

Sandwich Assay

An immunoassay; the solid phase (such as a biochip) for the assay is coated or spotted with antibodies. When the antigen is added in the first step, the antigen binds to the antibody. Then a second antibody, or conjugate, is added, the conjugate is labelled with an enzyme soluble substrate to produce either a colour (ELISA) or a chemiluminescent signal (biochips). The strength of the signal can be measured and used to calculate the analyte concentration.

SCE

The Scandinavian Committee on Enzymes

Screening

Screening is conducted to detect diseases and conditions at an early stage within an at-risk group. Its main aim is to identify those individuals who have disease-causing pathogens in their system and thus initiate effective treatment as quickly as possible.

Semi-automated

Semi-automated methods still require some interaction by the operator. The pipetting of reagents and reaction incubation steps are carried out manually however results are read and calculated by the analyser.

Sensitivity

The ability to detect small quantities of a measured component.

Serum

The clear amber liquid that is derived from clotted blood by centrifuging and removing the red blood cells.  Serum is a complex mixture of hundreds of different proteins, sugars, fats and salts and is the starting material for most diagnostic tests.  Many control products are serum based to ensure the matrix is the same as the patient sample.

Shift

The term shift is often used to describe an abrupt or sudden change in results.

Specificity

The ability of a method to measure solely the component of interest.

Spectrophotometer

An instrument for measuring the relative light intensities.

Spectrum

Different wavelengths of light occur when any form of light (e.g. white light, UV) is dispersed. The different wavelengths can then be filtered and used to perform various photometric assays for the detection of different analytes.

Stability

The shelf life of a substance or component after manufacture it has been opened or reconstituted.

Standard

An aqueous solution containing a known level or concentration of analyte that will not change and can be used to calculate diagnostic results.  Normally used to calibrate manual or semi-automated tests.

Standardisation

Standardisation is the process of developing and agreeing upon technical standards.

Standard deviation (SD)

The standard deviation of a normal distribution is a measure of the scatter or dispersion of

observations about the mean in the same units as the observations themselves. The standard deviation quantifies the degree of dispersion of data points around the mean.

Standard Deviation Index (SDI)

The standard deviation Index (SDI) expresses the deviation of the participant’s result (in SD units) from the mean. The SDI facilitates the comparison of results from different tests at the same time, without having to consider different units or magnitude of change. An average SDI of 1.0 or greater indicates that the test result shows a systematic difference from the group. The ideal SDI is zero, which would be the case if your result exactly matched the peer group mean.

SDI = Mean – Peer Group Mean / SD of Peer Group Mean

Substrate

The specific biochemical compound or compounds which an enzyme will act upon and convert into product.

T

Target Score

The target score relates the percentage deviation from the mean to a target percentage deviation.  The aim is to achieve a deviation smaller than the target % deviation.  The lower the deviation in relation to the target deviation the higher the target score.

Titer

A value expressed as a fraction that gives the highest dilution of a solution in which a particular analyte can still be measured e.g. Antibody titer.

Third Party

Third party controls are controls that are not designed or optimised for use with a specific reagent manufacturer or analyser thus reducing the potential of bias and providing a true assessment of performance.

Throughput

The term throughput is used in clinical chemistry to describe the number of tests an analyser is capable of carrying out in a given time period.

Traceability

Traceability ensures that laboratory results can be traced back to standards and methods that are recognised as accurate

Trend

The term trend is used to describe a gradual change in QC results over time.

Troponin T (or I)

A sensitive and specific marker of myocardial infarction

U

Unassayed

Unassayed controls are generally referred to as precision controls and are used only for the control of reproducibility of results. Lot specific approximate values are assigned from a consensus mean of results from independent laboratories for the most common method.

UV Method

A method of determining the concentration of a particular analyte in a blood sample.  The molecule of interest absorbs UV light and creates a detectable signal proportional to the analyte concentration.

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