NEET PG key terms

The proportion of people who truly have a disease and are correctly identified as positive by a test. It measures a test's ability to detect disease and is calculated as true positives divided by true positives plus false negatives.

The proportion of people without a disease who are correctly identified as negative by a test. It reflects how well a test excludes disease and is calculated as true negatives divided by true negatives plus false positives.

The probability that a person with a positive test result actually has the disease. Unlike sensitivity, it depends strongly on disease prevalence in the population tested, so it falls when prevalence is low.

A ratio comparing the probability of a given test result in people with disease to that in people without disease. Positive and negative likelihood ratios summarise test performance and allow updating of pre-test probability to post-test probability.

The number of patients who must receive a treatment for one additional patient to experience a defined beneficial outcome. It is the reciprocal of the absolute risk reduction, so a smaller value means a more effective intervention.

The ratio of the incidence of an outcome in an exposed group to the incidence in an unexposed group. It quantifies how many times more or less likely an event is with exposure and is used in cohort studies.

The ratio of the odds of exposure among cases to the odds of exposure among controls. It estimates the strength of association in case-control studies and approximates relative risk when the disease is rare.

The arithmetic difference in event rates between a control group and a treated group. It expresses the actual percentage of patients helped by an intervention and is used to derive the number needed to treat.

Indirect protection of susceptible individuals that arises when a sufficiently high proportion of a population is immune to an infection, interrupting transmission chains. The threshold depends on how contagious the pathogen is.

The proportion of a defined population that develops a disease during a limited outbreak or after a specific exposure. It is a measure of incidence used in field epidemiology to identify the source of an outbreak.

Programmed cell death in which a cell shrinks, chromatin condenses, and the cell breaks into membrane-bound bodies cleared without inflammation. It is energy-dependent and removes damaged or unwanted cells under genetic control.

Uncontrolled cell death caused by severe injury, marked by cell swelling, membrane rupture, and leakage of contents that triggers inflammation. Common patterns include coagulative, caseous, and liquefactive types.

A reversible change in which one mature cell type is replaced by another mature cell type, usually as an adaptive response to chronic irritation. An example is squamous metaplasia of bronchial epithelium in smokers.

Disordered growth in which cells show variation in size and shape and loss of normal orientation, but the change does not cross the basement membrane. It is considered pre-malignant and is graded by severity.

A malignant epithelial proliferation confined to the epithelium, with full-thickness cytological atypia but no invasion through the basement membrane. It has not metastasised but can progress to invasive cancer.

A description of how closely tumour cells resemble normal tissue, based on differentiation and mitotic activity. Higher grade means poorer differentiation and generally more aggressive behaviour, guiding prognosis and treatment.

The extent of cancer spread at diagnosis, including tumour size, lymph node involvement, and distant metastasis. It is the strongest prognostic factor for most cancers and determines treatment strategy.

The lowest concentration of an antimicrobial that prevents visible growth of a standardised bacterial inoculum after incubation. It quantifies susceptibility and guides dosing and breakpoint interpretation.

The lowest concentration of an antimicrobial that kills a defined proportion, usually 99.9 percent, of the bacterial inoculum. It is determined by subculturing from tubes showing no visible growth.

A defined minimum inhibitory concentration value that categorises an organism as susceptible, intermediate, or resistant to an antibiotic. Breakpoints are set using pharmacokinetic and clinical outcome data and are updated periodically.

Persistent suppression of bacterial growth after a brief exposure to an antibiotic, even when the drug concentration falls below the minimum inhibitory concentration. It supports extended-interval dosing of some agents such as aminoglycosides.

The ratio of the dose producing toxicity to the dose producing the desired therapeutic effect. A narrow index means small dose changes can cause harm, so drugs such as digoxin and lithium need therapeutic drug monitoring.

The apparent volume in which a drug dose would need to be dissolved to give the observed plasma concentration. It reflects tissue distribution rather than true anatomical space and guides loading dose calculation.

The volume of plasma from which a drug is completely removed per unit time. It determines the maintenance dose needed to sustain a target steady-state concentration and is influenced by hepatic and renal function.

Metabolism of an orally administered drug in the gut wall and liver before it reaches systemic circulation, reducing its bioavailability. Drugs with extensive first-pass effect often require higher oral doses or alternative routes.

The time taken for the plasma concentration of a drug to fall by half, determined by clearance and volume of distribution. It predicts how long a drug acts and how often it must be dosed.

A family of cysteine proteases that execute apoptosis by cleaving structural and regulatory proteins. Initiator caspases activate effector caspases in a cascade triggered by intrinsic or extrinsic death signals.

A 3-to-15 score assessing eye opening, verbal response, and motor response to grade level of consciousness. Scores of eight or below indicate severe impairment and prompt consideration of airway protection.

Elevation of pressure within the rigid skull above normal limits, causing headache, vomiting, papilloedema, and reduced consciousness. Unrelieved pressure can cause herniation and brainstem compression, which may be fatal.

Irreversible loss of brainstem function in a patient on a ventilator, demonstrated by absent cranial nerve reflexes and no respiratory effort despite adequate carbon dioxide challenge. It is legally equivalent to death in many jurisdictions.

A patient's voluntary agreement to a procedure after receiving and understanding information about its nature, risks, benefits, and alternatives. It requires capacity and can be withdrawn at any time.

A person's ability to understand, retain, weigh, and communicate a decision about their own care. It is assessed for the specific decision at hand and, if absent, care proceeds in the patient's best interests.

The duty to keep patient information private and disclose it only with consent or where law or public safety requires. Breach without justification is a professional and legal failing.

The period from delivery of the placenta until about six weeks postpartum, during which the uterus involutes and most reproductive tract changes resolve. It is when postpartum haemorrhage, sepsis, and thromboembolism may present.

Blood loss of 500 millilitres or more after vaginal delivery, or 1000 millilitres or more after caesarean, with or without haemodynamic compromise. Uterine atony is the commonest cause and is managed with uterotonics and resuscitation.

New hypertension after 20 weeks of gestation with proteinuria or other maternal organ dysfunction. It can progress to seizures, haemolysis, and placental insufficiency, and delivery remains the definitive treatment.

Stiffening of muscles after death caused by depletion of ATP, which prevents actin and myosin from separating. It begins in small muscles within hours, peaks, then resolves as decomposition proceeds, helping estimate time since death.

Purplish discolouration of dependent skin after death as blood settles under gravity in relaxed vessels. Its pattern and fixity help estimate time since death and can indicate whether a body was moved.

The gradual cooling of a body after death until it reaches ambient temperature. The rate of cooling is used, with caution, to estimate the post-mortem interval, since environment and body size alter it.