Overview of Clinical Chemistry and Laboratory Management

Comprehensive vocabulary flashcards covering laboratory mathematics, metrics, solutions, quality control parameters, statistics, control charts, and quality assurance in clinical chemistry.

Measurement

The determination of the dimensions, capacity, quantity, or extent of something in chemical laboratories.

English System

A measurement system used in countries such as the United States utilizing units like pounds, yards, miles, and pints.

Metric System

A system of measurement derived from the Greek word 'metron' meaning measure, used in scientific work including units like gram, meter, and liter.

International System of Units (SI Units)

Le Système international d'unites; the modern form of the metric system and world's most widely used measurement system in science and commerce.

Basic Units

Units that do not take support of other physical quantities for their measurement, consisting of 7 base units.

Derived Units

Quantities that are derived from the 7 base units.

Non-SI Units

Units that are so widely used that they have become acceptable for use alongside SI basic or SI-derived units.

Solution

A homogenous mixture of two or more substances with each substance retaining its own chemical identity.

Solvent

The component of a solution that is present in the greatest amount.

Solute

A component of a solution that is present in a lesser amount relative to that of the solvent.

Percent Weight/Weight

The number of grams of solute per 100 grams of solution.

Percent Volume/Volume

The amount of solute per 100 mL of solution.

Percent Weight/Volume

The number of grams of solute per 100 mL of solution.

Molarity

Concentration routinely expressed in units of moles per liter ($\text{mol/L}$), millimoles per liter ($\text{mmol/L}$), or $M$, calculated by dividing mass in grams by gram molecular weight.

Molality

The amount of solute per 1 kg of the solvent, expressed in terms of $\text{mol/kg}$ or $m$.

Clinical Chemistry

A basic science that utilizes chemistry to study human beings in various stages of health and disease by analyzing body fluids or tissue specimens.

Quality Control

A system and process of ensuring accuracy and precision in the laboratory by testing known samples resembling patient samples alongside measurements.

Sensitivity

The ability of an analytical method to measure the smallest concentration of the analytes of interest.

Specificity

The ability of an analytical method to measure only the analytes of interest.

Accuracy

The nearness or closeness of the assayed value to the target value.

Precision

The ability of an analytical method to give repeated results on the same sample that agree with one another.

Practicability

The degree by which a method is easily repeated.

Reliability

The ability of an analytical method to maintain accuracy and precision over an extended period of time despite changes in equipment, reagents, or personnel.

Diagnostic Sensitivity

The ability of the analytical method to detect the proportion of individuals with the disease.

Intralab Quality Control (Internal QC)

Analysis of control samples together with patient specimens for daily monitoring of accuracy and precision of analytic methods.

Interlab Quality Control (External QC)

Proficiency testing programs that periodically provide samples of unknown concentrations to participating laboratories to maintain long-term accuracy.

Control Solutions

Solutions whose stability and proper constitution determine the accuracy of an assay over time.

Control Limits

Expected values represented by intervals of acceptable values with upper and lower limits.

Variations

Errors encountered in the collection and measurement of samples, including transcriptions and releasing of laboratory results.

Random Error

A type of error present in all measurements that varies sample to sample, affecting precision.

Systematic Error

An error that influences observations consistently in one direction, detected as positive or negative bias.

Constant Error

A systematic error representing a continual difference between the comparative method and the test method regardless of concentration.

Proportional Error

Also known as slope or percentage error; results in greater deviation from the target value due to higher sample concentration.

Clerical Error

An error occurring highest in frequency with the use of handwritten labels and request forms.

Pre-Analytical Error

Errors occurring prior to sample testing, such as patient misidentification, improper preparation, or incorrect order of draw.

Analytical Error

Errors occurring during analysis, such as incorrect sample/reagent volume, improper incubation, or equipment malfunction.

Post-Analytical Error

Errors occurring after analysis, such as long turnaround times, incorrect data transcription, or results submitted to the wrong physician.

Statistics

The science of gathering, analyzing, interpreting, and presenting data.

Mean

A measure of central tendency.

Standard Deviation (SD)

A measure of the dispersion of values from the mean.

Coefficient of Variation (CV)

A percentile expression of the mean that serves as an index of precision.

Variance

The standard deviation squared; a measure of variability representing the difference between each value and the average data.

Inferential Studies

Studies used to compare the mean or standard deviations of two groups of data.

F-Test

A test used to determine whether there is a statistically significant difference between the standard deviations of two groups.

Median

The value of the observation that divides the distribution into two equal groups; the midpoint of a distribution.

Mode

The most frequent observation; used to describe data with two centers.

Range

The simplest expression of spread or distribution, calculated as the difference between the highest and lowest score.

Standard Deviation Index (SDI)

The difference between the value of a data point and the mean value divided by the group's SD.

Gaussian Curve

A bell-shaped curve obtained when a data set can be accurately described by the mean and SD.

Cumulative Sum Graph

A graph that calculates the difference between QC results and target means, commonly using a V-mask and requiring computer implementation.

Youden / Twin Plot

A plot used to compare results obtained on high and low control serum from different laboratories by plotting mean values on the ordinate and abscissa.

Shewhart Levey-Jennings Chart

The most widely used QC chart in clinical laboratories that identifies random and systematic errors and allows rule application without a computer.

Trend

A pattern formed on a QC chart when control values either increase or decrease for six consecutive days, mainly caused by reagent deterioration.

Shift

A pattern formed on a QC chart when control values distribute themselves on one side of the mean for six consecutive days, mainly caused by improper instrument calibration.

Outliers

Control values that are far from the main set of values due to random and systematic error, often caused by pipetting error.

Six Sigma

A performance improvement tool aimed at eliminating variation, improving quality, and reducing laboratory errors to near zero.

Lean System

A system conceptualized to reduce waste (non-value-added activities) using 5S and PDCA to increase operational efficiency.

Analytical Run

A set of control and patient specimens assayed, evaluated, and reported together.

Delta Check

A patient-based QC technique requiring computerized data to compare current patient results with past results.

Interference Experiments

Experiments used to measure systematic errors or inaccuracy caused by substances other than the analyte of interest.

Linear Range / Dynamic Range

The concentration range over which the measured concentration equals the actual concentration without modification of the method.

Physiologic Limit

Also referred to as an absurd value; helps detect sample contamination or sample dilution.

Point of Care Testing (POCT)

Decentralized analytical testing performed outside the confines of the central laboratory, usually by non-laboratory personnel.

Quality Assurance

Systematic action necessary to provide adequate confidence that laboratory services satisfy medical needs for patient care.

Recovery Experiment

An experiment showing whether a method measures all or part of an analyte to estimate systematic error or inaccuracy.

Predictive Value

A parameter depending on sensitivity, specificity, and disease prevalence that describes the relationship between post-test and pre-test probability of disease.

Reference Value

A value obtained by observation or measurement of a particular type of quantity on a reference individual.