Arab Board Clinical Pathology Part 1 key terms

The proportion of people who truly have a disease and are correctly identified as positive by a test. It reflects how well a test detects disease when disease is present.

The proportion of people without a disease who are correctly identified as negative by a test. It reflects how well a test excludes disease in healthy individuals.

The probability that a person with a positive test result actually has the disease. It depends on both test accuracy and the prevalence of the condition in the tested population.

The proportion of a population that has a condition at a given point in time. It strongly influences predictive values of diagnostic tests.

The number of new cases of a condition arising in a defined population over a specified period. It measures the rate at which new disease occurs.

A measure of relative dispersion calculated as the standard deviation divided by the mean, often expressed as a percentage. It allows comparison of variability between assays with different units or magnitudes.

A statistic quantifying the spread of values around the mean of a distribution. In the laboratory it is used to set control limits and describe analytical imprecision.

A quality control graph plotting control results over time against mean and standard deviation limits. It visually reveals shifts, trends, and random error in an analytical system.

A set of statistical rules applied to quality control data to decide whether a run should be accepted or rejected. They detect random and systematic error using control observations.

The routine analysis of control materials of known value alongside patient samples to monitor whether an analytical process is performing within acceptable limits on a daily basis.

A program in which an outside body sends unknown samples to many laboratories and compares their results, providing an objective check of inter-laboratory performance and accuracy.

Evaluation of laboratory performance by analyzing samples with values unknown to the laboratory and comparing results against peer or reference values. It is a form of external assessment.

The range of values, usually covering the central 95 percent of a healthy reference population, used to interpret whether a patient result is typical or abnormal.

The random variation observed when the same sample is measured repeatedly under defined conditions. It is commonly expressed as a standard deviation or coefficient of variation.

A systematic difference between the measured value and the true value, causing results to deviate consistently in one direction. It reflects inaccuracy rather than random variation.

The process of establishing the relationship between the signal produced by an instrument and the known concentration of a calibrator, so that patient results can be accurately quantified.

The property of a measurement result whereby it can be related to a stated reference, usually a national or international standard, through an unbroken chain of comparisons.

The principle stating that absorbance of light by a solution is proportional to the concentration of the absorbing substance and the path length. It underpins photometric assays.

An analytical technique measuring the intensity of light absorbed by a sample at a specific wavelength to determine the concentration of a substance in solution.

Diagnostic testing performed near or at the site of patient care, often by non-laboratory staff, giving rapid results but requiring its own quality assurance and operator competency programs.

A panel of hematologic measurements including hemoglobin, hematocrit, red cell indices, white cell count with differential, and platelet count, used to assess blood and its cellular components.

The average volume of a red blood cell, calculated from hematocrit and red cell count. It classifies anemia as microcytic, normocytic, or macrocytic.

The percentage or absolute number of newly released immature red cells in blood. It indicates the bone marrow's erythropoietic response to anemia.

A coagulation test measuring the time to clot after adding tissue factor and calcium, assessing the extrinsic and common pathways. It is expressed as a ratio or INR.

A standardized way of reporting prothrombin time, calculated by raising the prothrombin time ratio to the power of the thromboplastin's international sensitivity index, allowing comparison across laboratories.

A coagulation test that measures clotting time after activation of the intrinsic and common pathways. It is used to screen for factor deficiencies and to monitor heparin therapy.

A syndrome of widespread activation of coagulation causing microthrombi, consumption of platelets and clotting factors, and secondary bleeding. Laboratory findings include low platelets, prolonged clotting times, and elevated D-dimer.

A degradation product of cross-linked fibrin released when clots are broken down. Elevated levels support the presence of thrombosis but are nonspecific.

A technique that passes cells singly through a laser beam to measure size, granularity, and surface marker fluorescence, widely used in immunophenotyping of leukemias and lymphomas.

A numbered cell-surface antigen (CD antigen) used to identify and classify leukocyte populations by lineage and maturation stage in immunophenotyping and diagnostic hematology.

A plate-based immunoassay in which an enzyme-linked antibody or antigen produces a colorimetric signal proportional to the target analyte. It is widely used to detect antibodies and antigens.

The change from a negative to a positive antibody result following infection or vaccination, indicating an immune response has developed. It may be used to diagnose recent infection.

The interval after infection during which a pathogen is present but not yet detectable by a given assay, such as before antibodies appear or before antigen levels rise.

A group of molecular methods, such as polymerase chain reaction, that amplify specific pathogen nucleic acid sequences to detect infection with high sensitivity, often before antibodies appear.

A molecular technique that repeatedly copies a target DNA sequence using primers and a thermostable polymerase, enabling detection or amplification of minute amounts of genetic material.

In real-time polymerase chain reaction, the amplification cycle at which fluorescence crosses a defined threshold. Lower values generally indicate a higher initial amount of target nucleic acid.

The ordered arrangement of an individual's chromosomes, described by number and structural abnormalities. It is used to detect aneuploidy, translocations, and other large chromosomal changes.

A cytogenetic technique using fluorescently labeled DNA probes that bind complementary chromosome sequences, allowing detection of specific deletions, amplifications, or translocations in cells.

A screening immunoassay detecting antibodies directed against nuclear antigens. A positive result with a characteristic pattern supports evaluation for systemic autoimmune rheumatic disease.

A group of plasma proteins that, when activated in cascade, promote inflammation, opsonization, and cell lysis. Low levels may indicate consumption in immune-complex disease.

A pretransfusion test mixing donor red cells with recipient serum to detect incompatibility before transfusion. It complements ABO and antibody screening to ensure safe transfusion.

A test of recipient serum against reagent red cells to detect clinically significant unexpected antibodies before transfusion or pregnancy, guiding selection of compatible blood units.

The major blood group system defined by A and B antigens on red cells and naturally occurring anti-A and anti-B antibodies in plasma, determining transfusion compatibility.