ABPath Chemical Pathology key terms

The range of test results, usually spanning the central 95% of values from a defined healthy population, used to decide whether a patient result is typical or abnormal.

The random scatter of results when the same sample is measured repeatedly under stable conditions, reflecting imprecision of the method and expressed as a coefficient of variation.

A systematic shift of results away from the true value, caused by calibration error, interference, or method differences, that affects accuracy rather than imprecision.

The combined effect of random imprecision and systematic bias on a measurement, used to judge whether a method meets a defined allowable performance standard.

A control chart plotting quality control results over time against mean and standard deviation lines, allowing visual detection of shifts, trends, and out-of-range values.

A set of statistical rules applied to quality control data, such as 1-3s and 2-2s, that flag runs for rejection when results suggest random or systematic error.

A comparison of a patient's current result with their previous result, flagging unexpectedly large changes that may indicate specimen mix-up, collection error, or a true clinical change.

A statistic describing the average spread of values around the mean, used to set control limits and express imprecision in laboratory quality control.

The standard deviation expressed as a percentage of the mean, permitting comparison of imprecision between assays or analyte concentrations of different magnitude.

The smallest amount of analyte a method can reliably distinguish from zero, often expressed as the limit of detection or limit of quantification.

The ability of a method to measure only the intended analyte without interference from related substances, cross-reactants, or matrix components.

A substance or condition in a specimen, such as hemolysis, lipemia, icterus, or a cross-reacting drug, that falsely alters the measured result.

The span of analyte concentrations over which a method's response is proportional to concentration, beyond which dilution or reanalysis is required.

The process of establishing the mathematical relationship between instrument signal and known analyte concentrations using calibrator materials, so patient results can be quantified.

Infection-control practices applied to all specimens and patients, including hand hygiene and use of gloves, gowns, and eye protection to prevent exposure to bloodborne pathogens.

The prescribed sequence for filling blood collection tubes, designed to prevent additive carryover between tubes that could alter chemistry, hematology, or coagulation results.

Rupture of red cells releasing hemoglobin and intracellular contents into plasma, which can falsely raise potassium, LDH, and AST and interfere with many colorimetric assays.

Instructions given before specimen collection, such as fasting, timing relative to medications or meals, and posture, that ensure results are interpretable and comparable to reference data.

A spuriously elevated serum potassium caused by cell breakdown during collection or clotting, as in hemolysis, delayed processing, or difficult venipuncture, rather than true in vivo elevation.

The difference between measured cations and anions, calculated as sodium minus chloride and bicarbonate, used to classify metabolic acidosis into high-gap and normal-gap causes.

The difference between measured osmolality and calculated osmolality, elevated when unmeasured osmotically active substances such as alcohols or glycols are present.

The amount of acid or base needed to return blood to normal pH at standard conditions, indicating the metabolic component of an acid-base disturbance.

A calculation comparing the change in anion gap with the change in bicarbonate, used to detect mixed acid-base disorders such as concurrent metabolic alkalosis with high-gap acidosis.

An estimate of glomerular filtration rate derived from serum creatinine and timed urine collection or from prediction equations, used to assess kidney function and dose drugs.

A calculated index of kidney filtration derived from serum creatinine or cystatin C plus age and sex, used to stage chronic kidney disease and adjust medication dosing.

A cardiac muscle protein released into blood when myocardial cells are injured, measured by high-sensitivity immunoassay as the preferred biomarker for diagnosing acute myocardial infarction.

A clonal plasma cell disorder producing a single homogeneous immunoglobulin, detected as a sharp band on serum protein electrophoresis or by free light chain measurement.

Separation of serum proteins by charge into albumin, alpha, beta, and gamma fractions, used to screen for monoclonal proteins and assess protein patterns.

An electrophoresis technique using specific antisera to identify the heavy and light chain type of a monoclonal protein band seen on serum or urine electrophoresis.

A standardized prothrombin time ratio corrected for thromboplastin sensitivity, used to monitor warfarin therapy and assess the extrinsic coagulation pathway.

A clotting test that measures the intrinsic and common coagulation pathways, used to screen for factor deficiencies and to monitor unfractionated heparin therapy.

Measurement of drug concentrations in blood at defined times to individualize dosing for drugs with narrow therapeutic ranges and unpredictable pharmacokinetics.

The drug concentration measured just before the next dose, representing the lowest steady-state concentration and often the preferred sampling time for therapeutic monitoring.

Analytical testing performed near the patient by non-laboratory staff, requiring its own quality control, operator competency, and result documentation outside the main laboratory.

Population testing of newborns, usually from dried blood spots, for treatable congenital disorders such as hypothyroidism, phenylketonuria, and hemoglobinopathies.

An inherited deficiency of phenylalanine hydroxylase causing phenylalanine accumulation and intellectual disability if untreated, detected by newborn screening and managed with dietary restriction.

The interval from specimen receipt or order entry to result reporting, a key performance indicator used in laboratory management and clinical decision-making.

A result so far outside normal limits that it signals imminent danger to the patient and requires immediate notification of the responsible clinician with documentation.