MELE key terms

A test that mixes a patient's serum with reagent red cells and anti-human globulin to detect unexpected antibodies against red cell antigens before transfusion or during pregnancy.

An antibody formed after exposure to foreign red cell antigens through transfusion or pregnancy, directed against antigens the person lacks; unlike autoantibodies, it reacts with donor cells.

The compatibility test that mixes recipient serum with donor red cells, with or without anti-human globulin, to confirm no clinically significant incompatibility exists before transfusion.

A mismatch between forward (cell) and reverse (serum) ABO typing results, caused by weak subgroups, missing antibodies, extra antibodies, or technical error, requiring resolution before transfusion.

Serial dilution of serum to measure antibody strength, reported as the highest dilution showing reactivity; used for prenatal anti-D monitoring and for assessing ABO-incompatible transplant risk.

A test detecting antibody or complement coating a patient's own red cells in vivo, using anti-human globulin; positive results suggest autoimmune hemolysis, drug-induced hemolysis, or hemolytic disease of the newborn.

The central range of results, usually covering the middle 95% of a healthy reference population, against which a patient result is compared to flag possible abnormality.

The smallest amount of analyte a method can reliably distinguish from zero, often expressed as the limit of detection; distinct from functional sensitivity and from clinical sensitivity.

A substance or condition in the sample, such as hemolysis, lipemia, icterus, or a cross-reacting drug, that alters measured analyte concentration and biases the result.

A quality rule that compares a patient's current result with a previous result and flags differences exceeding a set limit, catching specimen mix-ups, mislabeling, and acute changes.

The calculated difference between measured cations and anions, usually sodium minus chloride and bicarbonate; an elevated value suggests unmeasured anions such as ketoacids, lactate, or toxins.

The difference between measured osmolality and calculated osmolality; an increased gap indicates unmeasured osmotically active particles such as ethanol, methanol, ethylene glycol, or isopropanol.

A panel measuring red cell count, hemoglobin, hematocrit, red cell indices, white cell count and differential, and platelet count, used to screen and monitor hematologic and systemic disease.

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

The percentage or absolute number of young red cells still containing RNA, reflecting marrow response; a high count indicates blood loss or hemolysis, a low count suggests production failure.

Microscopic examination of a stained blood film to assess cell morphology, platelet adequacy, and white cell distribution, confirming or explaining automated analyzer findings.

The lowest antimicrobial concentration that visibly inhibits growth of a standardized bacterial inoculum, used to categorize an isolate as susceptible, intermediate, or resistant.

An agar-based susceptibility method in which antibiotic-impregnated disks diffuse into inoculated agar; zone diameters are compared with published breakpoints to categorize susceptibility.

A published concentration or zone-diameter threshold that separates susceptible from resistant organisms for a given drug, organism group, and testing method.

Culture media that suppress unwanted organisms and reveal distinguishing biochemical traits, such as MacConkey agar inhibiting gram-positives while differentiating lactose fermenters by colony color.

The visible characteristics of a bacterial colony on agar, including size, shape, color, hemolysis, and texture, used with Gram stain to guide identification.

A method using an enzyme-linked antibody to detect or quantify antigen or antibody through a color-producing substrate reaction; widely used for screening serology and hormone testing.

A false-negative or falsely low immunoassay result caused by very high antibody excess, which prevents immune complex lattice formation; resolved by diluting the specimen and retesting.

The appearance of detectable specific antibody or antigen after infection or vaccination, marked by a change from negative to positive; paired sera showing rising titer support recent infection.

A measure of urine density relative to water, reflecting the kidney's concentrating ability; assessed by refractometry or reagent strip and useful in evaluating hydration and renal function.

Examination of urine sediment for cells, casts, crystals, and organisms; findings such as red cell casts localize disease to the kidney and guide diagnosis.

A dipstick with reagent pads that change color to screen for pH, protein, glucose, ketones, blood, leukocyte esterase, nitrite, and other analytes; results require confirmation by microscopy.

A control chart plotting quality control values over time with mean and standard deviation limits, making shifts, trends, and random error visible for daily assay monitoring.

Statistical multirule criteria, such as 1-3s, 2-2s, R-4s, and 4-1s, applied to quality control data to decide whether an analytical run should be accepted or rejected.

A program that sends unknown specimens to many laboratories and compares each result with peer or reference values, providing objective evidence of analytical performance.

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

The PCR cycle at which fluorescence first exceeds background; lower values indicate more starting target, while high values near the limit of detection require cautious interpretation.

Practices preventing amplicon or specimen carryover from causing false positives, including unidirectional workflow, separate pre- and post-amplification areas, aliquoted reagents, and negative controls.

Infection control practices applied to all patients, including hand hygiene, gloves, gowns, masks, and safe sharps handling, based on the assumption that any specimen may carry transmissible agents.

A ventilated enclosure using HEPA-filtered airflow to protect workers and the environment, and in some classes the product, when handling infectious aerosols or manipulating cultures.

A standardized document supplied with a hazardous chemical that lists hazards, handling precautions, exposure controls, first aid, and spill response, required to be accessible to laboratory staff.