RRB Lab Technician key terms

Microorganisms that live harmlessly on or inside the human body, such as skin staphylococci and gut coliforms, and can cause infection when they move to another site or the host's immunity falls.

A microbe that rarely harms a healthy person but causes disease when immunity is low, normal barriers break, or it enters an unusual site such as the bloodstream or urinary tract.

An infection acquired in a hospital or other healthcare setting that was not present or incubating at the time of admission, often spread by hands, equipment, or contaminated surfaces.

A set of practices that keep equipment, media, and work areas free of living microbes, including flaming loops, working near a flame, and never touching sterile surfaces with ungloved hands.

A pressure vessel that sterilises materials using saturated steam at about 121 degrees Celsius and 15 psi for 15 to 20 minutes, killing spores as well as vegetative bacteria.

A dry-heat steriliser held at 160 to 170 degrees Celsius for about two hours, used for glassware, metal instruments, and powders that steam cannot penetrate well.

A prepared mixture of nutrients that supports microbial growth, containing a carbon source, nitrogen, salts, water, and often selective or indicator substances for identifying particular organisms.

A culture medium containing substances that inhibit unwanted organisms while allowing the target group to grow, such as bile salts agar for enteric bacteria or mannitol salt agar for staphylococci.

A medium with indicators that let colonies of different species look distinct, for example MacConkey agar turning pink for lactose fermenters and pale for non-fermenters.

A differential staining method using crystal violet, iodine, alcohol, and safranin that divides bacteria into purple Gram-positive and pink Gram-negative groups based on cell wall structure.

An acid-fast staining method using hot carbol fuchsin and acid-alcohol decolouriser that leaves mycobacteria appearing red against a blue background of non-acid-fast cells.

A visible mass of microbial cells on a solid medium that grew from a single organism or group, whose size, shape, colour, and edge help identify the species.

A laboratory procedure, usually disc diffusion, that measures how well an isolated organism responds to various antibiotics so clinicians can choose effective therapy.

The lowest concentration of an antimicrobial agent that visibly prevents growth of a test organism, used to guide dosing and to classify isolates as susceptible or resistant.

A panel of haematology measurements including haemoglobin, red cell count, haematocrit, white cell count with differential, and platelet count, used to screen and monitor many disorders.

The iron-containing protein in red cells that carries oxygen from the lungs to tissues; its concentration is measured in grams per decilitre and falls in anaemia.

The percentage of blood volume occupied by red cells after centrifugation, used to assess anaemia, hydration, and red cell production alongside haemoglobin.

A count of the proportions of neutrophils, lymphocytes, monocytes, eosinophils, and basophils in blood, used to distinguish bacterial, viral, allergic, and other conditions.

The number of platelets per microlitre of blood, normally about 150,000 to 450,000, with low values raising bleeding risk and high values raising clotting risk.

The distance red cells fall in a vertical tube in one hour, a non-specific marker of inflammation that rises with infection, tissue damage, and certain anaemias.

A laboratory test of clotting function such as prothrombin time or activated partial thromboplastin time, used to monitor anticoagulant therapy and detect bleeding disorders.

An acute-phase protein made by the liver that rises quickly with inflammation and infection; a sensitive but non-specific marker, measured in serum or plasma.

The clear fluid left after blood clots and the cells and fibrin are removed, containing antibodies, proteins, hormones, and metabolites, and used for most biochemical and serological tests.

The liquid part of unclotted blood containing fibrinogen and all other proteins, obtained by centrifuging blood collected in an anticoagulant tube such as EDTA or citrate.

A substance added to blood collection tubes to prevent clotting, such as EDTA for haematology, sodium citrate for coagulation studies, or heparin for some chemistry tests.

The puncture of a vein with a needle to collect blood, usually from the antecubital fossa, requiring correct order of draw, asepsis, and proper tube mixing.

The physical, chemical, and microscopic examination of urine, checking colour, specific gravity, pH, protein, glucose, ketones, blood, and cells or casts under the microscope.

The ratio of a fluid's density to that of water, showing how concentrated urine is and reflecting the kidney's ability to concentrate or dilute it.

The interval of values expected in healthy people of a defined population, used to judge whether a patient's result is low, normal, or high.

The routine testing of known control samples alongside patient samples to confirm that an assay is performing within acceptable limits before results are reported.

Setting or checking an instrument against standards of known concentration so that measured signals correspond correctly to the quantity being reported.

A graded set of containment practices, equipment, and facility design, from level 1 to level 4, matched to the risk of the organisms handled in a laboratory.

Waste generated in healthcare such as used needles, blood-soaked material, and cultures, which must be segregated by colour-coded containers and disposed of by approved methods.

The arithmetic average of a set of values, found by adding all observations and dividing by their number; sensitive to extreme values.

The middle value of an ordered data set, or the average of the two middle values when the count is even; less affected by outliers than the mean.

A measure of how widely values spread around the mean, equal to the square root of the average squared deviation from the mean.

A fraction expressed out of one hundred, calculated by dividing the part by the whole and multiplying by 100, commonly used for concentrations and recovery rates.

A relationship showing how two quantities compare, used to solve dilution, dosage, and scaling problems by setting two equivalent fractions equal and cross-multiplying.

A stepwise series of dilutions in which each tube is made from the previous one, used to obtain very low concentrations or countable colony numbers from dense samples.