ASCP MLS key terms

Testing the patient's serum against reagent red cells of known A and B type to detect naturally occurring anti-A and anti-B; results should mirror the forward type, and any mismatch must be resolved before transfusion.

Detects antibody or complement bound to a patient's red cells in vivo by adding antihuman globulin; used to investigate hemolytic disease of the newborn, autoimmune hemolysis, and suspected transfusion reactions.

Antibody recovered from washed, sensitized red cells by techniques such as heat, acid, or an organic solvent; testing the eluate helps identify the antibody causing a positive direct antiglobulin test.

Anti-D antibody given to D-negative women during pregnancy and after delivery of a D-positive infant to prevent alloimmunization; the dose is based on the size of the fetomaternal bleed.

Acid-elution stain that identifies fetal hemoglobin-containing cells in maternal blood; the percentage of fetal cells estimates the volume of fetomaternal hemorrhage and guides Rh immune globulin dosing.

Red cells, platelets, or granulocytes exposed to ionizing radiation to inactivate donor T lymphocytes; prevents transfusion-associated graft-versus-host disease in immunocompromised or related-donor recipients.

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

Difference between measured osmolality and calculated osmolality; an increased gap indicates an unmeasured osmotically active substance such as methanol, ethylene glycol, or isopropanol.

Glomerular filtration rate calculated from serum creatinine plus age, sex, and sometimes race using a validated equation; used to stage chronic kidney disease and adjust drug doses.

Spectrophotometric measure of free hemoglobin in a serum or plasma sample that flags hemolysis interference; strong hemolysis can falsely raise potassium, LDH, and AST and alter other analytes.

Calcium value adjusted for albumin concentration, since roughly half of serum calcium is protein bound; the correction helps interpret total calcium when albumin is low or high.

Comparison of a current result with the patient's previous result within a defined interval; significant differences are investigated to detect specimen mislabeling, contamination, or genuine clinical change.

Glycated hemoglobin reflecting average glucose over roughly the previous two to three months; reported as a percentage of total hemoglobin or in mmol/mol and used to monitor diabetes.

Reticulocyte percentage adjusted for the degree of anemia, giving a better estimate of marrow response; a low corrected count suggests inadequate production despite anemia.

Incubating patient plasma with normal pooled plasma to see whether a prolonged coagulation time corrects; correction suggests factor deficiency, while failure to correct suggests an inhibitor such as heparin or a lupus anticoagulant.

Measure of the variation in red cell size; a high value indicates anisocytosis and helps distinguish types of anemia, such as iron deficiency versus thalassemia trait.

Fibrin degradation product released when cross-linked fibrin is broken down; a negative result helps exclude venous thromboembolism, while elevated values are nonspecific and occur in many conditions.

Calculated by multiplying the white blood cell count by the percentage of neutrophils and bands; used to assess infection risk and to define neutropenic fever thresholds.

False-negative or falsely low antibody result caused by antibody excess that prevents lattice formation; resolves when the sample is diluted and retested.

Screening test in which patient serum is applied to slides of cultured cells and bound antibody is detected with fluorescent anti-human globulin; the pattern and titer suggest specific connective tissue diseases.

Identification of human leukocyte antigen alleles, usually by molecular methods, for donor-recipient matching before transplantation and for disease association or drug hypersensitivity testing.

Technique that passes single cells through a laser and measures light scatter and fluorescence; used for lymphocyte subsets, leukemia immunophenotyping, and paroxysmal nocturnal hemoglobinuria testing.

Lowest concentration of an antimicrobial that visibly inhibits growth of a standardized inoculum; used with breakpoints to classify an organism as susceptible, intermediate, or resistant.

Enzyme produced by some Enterobacterales that hydrolyzes penicillins and cephalosporins, including third-generation agents; detection matters because infections may require carbapenems or other alternatives.

Method that identifies bacteria and yeast by comparing their protein mass spectra with a reference library; results are available within minutes of obtaining a colony.

Selective and differential medium containing bile salts and crystal violet that inhibit gram-positive organisms; lactose fermenters produce pink colonies, while nonfermenters remain colorless.

Growth of organisms introduced during collection rather than from the bloodstream, often coagulase-negative staphylococci or diphtheroids; rates are monitored because contaminants cause unnecessary antibiotics and cost.

In real-time PCR, the cycle at which fluorescence first exceeds a threshold; lower values indicate more target nucleic acid, and results are only valid within the assay's reportable range.

Heating an amplified product while monitoring fluorescence to identify the temperature at which double-stranded DNA separates; used to distinguish amplicons or detect sequence variants.

Uses fluorescently labeled DNA probes that bind complementary chromosomal sequences in fixed cells; used to detect translocations, amplifications, and deletions in tumors.

Amplification of several targets in one reaction using multiple primer pairs; requires careful primer design and optimization to avoid preferential amplification and cross-reactivity.

Cylindrical mold of the renal tubule containing red cells, indicating glomerular bleeding; a key finding that points to glomerulonephritis rather than lower urinary tract bleeding.

Ratio of protein to creatinine in a spot urine sample that estimates 24-hour protein excretion; avoids timed collections and is used to assess and monitor kidney disease.

Measure of urine density compared with water, reflecting the kidney's ability to concentrate or dilute; reagent strip methods are affected by pH and protein, so refractometry is often preferred.

Examination of joint fluid under polarized light for crystals; negatively birefringent needle-shaped urate crystals indicate gout, while positively birefringent rhomboid calcium pyrophosphate crystals indicate pseudogout.

External program that sends unknown samples to laboratories and compares results with peer groups; acceptable performance is required for accreditation and helps reveal systematic error.

Documented evaluation of staff skills, typically including direct observation, result review, and blind sample testing; required at defined intervals and whenever new methods or instruments are introduced.

Structured investigation of an adverse event or error that traces contributing factors in process, equipment, and human performance rather than assigning blame to an individual.