Basic Principles and Practices Flashcards
Quantitative science that is concerned with measurement of amounts of biologically important substances (analytes) in body fluids
Clinical Chemistry
What is the primary purpose of a clinical chemistry laboratory
To facilitate the correct performance of analytic procedures that yield accurate and precise information, aiding patient diagnosis and treatment
It defines the physical quantity or dimension
Unit
A system preferred in scientific literature and clinical laboratories and is the only system employed in many countries
Système International d’Unités (SI)
Système International d’Unités (SI), adopted internationally in
1960
The SI system units are based on
Metric system
Subclassifications of SI system
Basic unit
Derived units
Non-SI units
This group develops standards of practice, definitions, and guidelines that can be adopted by everyone in a given field, providing for more uniform terminology and less confusion
International Organization for Standardization
Reporting of laboratory results is often expressed in terms of
Substance concentration or the mass of a substance
Varying grades of purity of analytic chemicals
Analytic reagent (AR)
Ultrapure
Chemically pure (CP)
United States Pharmacopeia (USP)
National Formulary (NF)
Technical or commercial grade
Purity grade of the chemical that is specified by American Chemical Society
Analytic reagent (AR) grade chemicals
Chemicals of this category are suitable for use in most analytic laboratory procedures
Analytic reagent (AR)
Chemicals that have been put through additional purification steps for use in specific procedures such as chromatography, atomic absorption, immunoassays, molecular diagnostics, standardization, or other techniques that require extremely pure chemicals
Ultrapure chemicals
These reagents may carry designations of HPLC (high-performance liquid chromatography) or chromatographic on their labels
Ultrapure chemicals
Chemicals used to manufacture drugs
United States Pharmacopeia (USP); National Formulary (NF) grade chemicals
The limitations established for this group of chemicals are based only on the criterion of not being injurious to individuals
United States Pharmacopeia (USP); National Formulary (NF) grade chemicals
Chemicals that are pure enough for use in most chemical procedures
United States Pharmacopeia (USP); National Formulary (NF) grade chemicals
Impurity limitations are not stated and that preparation of these chemicals is not uniform
Chemically pure (CP) or pure grade
Analysis often used to ascertain the acceptable purity range of chemically pure (CP) grade chemicals
Melting point analysis
These chemicals are not recommended for clinical laboratories use for reagent preparation unless further purification or a reagent blank is included
Chemically pure (CP) or pure grade
Chemicals used primarily in manufacturing and should never be used in the clinical laboratory
Technical or commercial grade reagents
Organic reagents with some impurities
Practical grade
Organic reagents which approaches the purity level of reagent grade chemicals
Chemical pure
Purity levels of these chemicals are attained by their respective procedures
Spectroscopic (spectrally pure) and chromatographic grade organic reagents
Chemicals certified to contain impurities below certain levels established by the ACS
Reagent grade (ACS)
It requires manufacturers to clearly indicate the lot number, plus any physical or biologic health hazard and precautions needed for the safe use and storage of any chemical
Occupational Safety and Health Administration (OSHA)
They are required to provide technical data sheets for each chemical manufactured on a document called a Material Safety Data Sheet (MSDS)
Chemical manufacturers
Highly purified chemical that can be measured directly to produce a substance of exact known concentration and purity
Primary standard
ACS purity tolerances for primary standards
100 ± 0.02%
Developed certified standard reference materials/ SRMs for use in clinical chemistry laboratories
National Institute of Standards and Technology (NIST)
Used when producing calibrator and standard materials
NIST SRM
Substance of lower purity, with its concentration determined by comparison with a primary standard
Secondary standard
The composition of this standard cannot be directly determined
Secondary standard
This standard depends on analytic reference method
Secondary standard
Most frequently used reagent in the laboratory
Water
Water solely purified by distillation results in
Distilled water
Water purified by ion exchange produces
Deionized water
Reverse osmosis, which pumps water across a semipermeable membrane, produces
RO water
Other methods for water purification
Ultrafiltration
Ultraviolet light
Sterilization
Ozone treatment
Clinical and Laboratory Standards Institute (CLSI), classified reagent grade water into six categories based on
Specifications needed for its use
Categories of reagent grade water
Clinical laboratory reagent water (CLRW)
Special reagent water (SRW)
Instrument feed water
Water supplied by method manufacturer
Autoclave and wash water
Commercially bottled purified water
Water monitoring parameters
Microbiological count
Resistivity
pH
Organics
Particulate matter
Silicate
Type of water with the most stringent requirements and generally suitable for routine laboratory use
Type I
Process that can remove particulate matter from municipal water supplies before any additional treatments
Prefiltration
Composition of filtration cartridges
Glass
Cotton
Activated charcoal
Submicron filters
Pore size of submicron filters
≤0.2 mm
Function of activated charcoal in filtration cartridge
Removes organic materials and chlorine
Function of submicron filter in filtration cartridge
Remove substances larger than the filter’s pores, including bacteria
Water that has been purified to remove almost all organic materials, using a technique of distillation
Distilled water
Water that has some or all ions removed, although organic material may still be present, so it is neither pure nor sterile
Deionized water
Water that is produced using either an anion or a cation exchange resin, followed by replacement of the removed ions with hydroxyl or hydrogen ions
Deionized water
Process that uses pressure to force water through a semipermeable membrane, producing water that reflects a filtered product of the original water
Reverse osmosis
Process that is excellent in removing particulate matter, microorganisms, and any pyrogens or endotoxins
Ultrafiltration and nanofiltration
Process that removes some trace organic material
Ultraviolet oxidation
Acceptable for glassware washing but not for analysis or reagent preparation
Type III/autoclave wash water
Type of water acceptable for most analytic requirements, including reagent, quality control, and standard preparation
Type II water
Type of water used to test methods requiring minimum interference, such as trace metal, iron, and enzyme analyses
Type I water
Why is it that storage for some reagent grade water is discouraged?
Because of the changes in resistivity
Storage requirement for Clinical Laboratory Reagent Water
CLRW should be stored in a manner that reduces any chemical or bacterial contamination and for short periods
Testing procedures to determine the quality of reagent grade water include measurements of
Resistance
pH
Colony counts
Chlorine
Ammonia
Nitrate or nitrite
Iron
Hardness
Phosphate
Sodium
Silica
Carbon dioxide
Chemical oxygen demand
Metal detection
The relationship of water purity to resistance
Linear, Generally, as purity increases, so does resistance
A substance that is dissolved in a liquid is called
Solute
In laboratory science, biologic solutes are also known as
Analytes
The liquid in which the solute is dissolved
Solvent
Solute and solvent together represent a
Solution
SI expression for the amount of a substance
Mole
Expressed as equal parts per hundred or the amount of solute per 100 total units of solution
Percent solution
Three expressions of percent solutions
Weight per weight (w/w)
Volume per volume (v/v)
Weight per volume (w/v)
Expressed as the number of moles per 1 L of solution
Molarity (M)
Represents the amount of solute per 1 kg of solvent
Molality (m)
The least likely encountered concentration expression in clinical laboratories, but it is often used in chemical titrations and chemical reagent classification
Normality
It is defined as the number of gram equivalent weights per 1 L of solution
Normality
Routine terms in the clinical laboratory that describe the extent of saturation
Dilute
Concentrated
Saturated
Supersaturated
A solution which there is relatively little solute or one which has been made to a lower solute concentration per volume of solvent as when making a dilution
Dilute solution
Solution that has a large quantity of solute in solution
Concentrated solution
A solution in which there is an excess of undissolved solute particles can be referred to as
Saturated solution
A solution that has an even greater concentration of undissolved solute particles than a saturated solution of the same substance
Supersaturated solution
The properties of osmotic pressure, vapor pressure, freezing point, and boiling point are called
Colligative properties
The pressure at which the liquid solvent is in equilibrium with the water vapor
Vapor pressure
The temperature at which the vapor pressures of the solid and liquid phases are the same
Freezing point
The temperature at which the vapor pressure of the solvent reaches one atmosphere
Boiling point
Predictable changes in the colligative properties when solute is dissolved in a solvent
Freezing point is lowered by -1.86°C
Boiling point is raised by 0.52°C
Vapor pressure is lowered by 0.3 mm Hg or torr
Osmotic pressure is increased by a factor of 1.7 × 10^4 mm Hg or torr
A measure of the ability of a solution to accept or donate electrons
Redox potential, or oxidation-reduction potential
Substances that donate electrons are called
Reducing agents
Substances that accept electrons are called
Oxidizing agents
A measure of how well electricity passes through a solution
Conductivity
The reciprocal of conductivity, is a measure of a substance’s resistance to the passage of electrical current
Resistivity
The primary application of resistivity in the clinical laboratory
For assessing the purity of water
Unit of expression of resistivity
Ohms
Unit of expression of conductivity
Ohms^-1 or mho
Refers to weak acids or bases and their related salts that, as a result of their dissociation characteristics, minimize changes in the hydrogen ion concentration
Buffers
Represents the negative or inverse log of the hydrogen ion concentration
pH
Mathematically describes the dissociation characteristics of weak acids and bases and the effect on pH
Henderson-Hasselbalch equation
The concentration or activity of ions in a solution or buffer
Ionic strength
The SI designation for temperature
Kelvin
Type of thermometer that uses a colored liquid (red or other colored material), or at one time mercury, encased in plastic or glass material with a bulb at one end and a graduated stem
Liquid-in-glass thermometers
Thermometers used for measuring temperatures in units such as heating blocks and water baths and should be immersed to the proper height as indicated by the continuous line etched on the thermometer stem
Partial immersion thermometers
Thermometer that requires the bulb and entire column of liquid be immerse into the medium measured, and are used for refrigeration applications
Total immersion thermometers
Thermometer used to check temperatures on flat surfaces, such as in an incubator or heating oven
Surface thermometers
Laboratory supplies consisted of some type of glass could be correctly termed
Glasswares
Class of laboratory supplies that satisfy ASTM precision criteria and are preferred for laboratory applications
Class A
Class of laboratory supplies that are identical to Class A, have twice the tolerance limits of Class A, and are often found in student laboratories where durability is needed
Class B
Designation for vessels that do not deliver the same volume when the liquid is transferred into a container
To contain (TC) devices
Designation for vessels that delivers exact amount of liquid
To deliver (TD) devices
Categories of glasswares
Kimax/Pyrex (borosilicate)
Corex (aluminosilicate)
High silica
Vycor (acid and alkali resistant)
Low actinic (amber colored)
Flint (soda lime) glass used for disposable material
Characteristics of laboratory plasticwares 
Resistance to corrosion and breakage
Flexible
Relatively inexpensive
The major types of resins frequently used in the clinical chemistry laboratory
Polystyrene
Polyethylene
Polypropylene
Tygon
Teflon
Polycarbonate
Polyvinyl chloride
Successful cleaning solutions for glasswares and plasticwares
Acid dichromate
Nitric acid
Type of cleaner used in the clinical laboratory that can help remove debris coating the surfaces of glass
Ultrasonic cleaners
The flask has a round, lower portion with a flat bottom and a long, thin neck with an etched calibration line
Volumetric flask
The flask that has a wide bottom that gradually evolves into a smaller, short neck
Erlenmeyer flask
Container that has a flat bottom, straight sides, and an opening as wide as the flat base, with a small spout in the lip
Griffin beaker
Laboratory vessel with long, cylindrical tubes usually held upright by an octagonal or circular base
Graduated cylinders
Glass or plastic utensils used to transfer liquids; they may be reusable or disposable
Pipets
Pipet that holds or contains a particular volume but does not dispense that exact volume
TC pipets
Pipet that will dispense the volume indicated
TD pipets
Pipet that has a continuous etched ring or two small, close, continuous rings located near the top of the pipet
Blowout pipet
Pipet that allows the contents of the pipet to drain by gravity
Self-draining pipet
A self-draining pipet without graduations to the tip. And the tip should not be allowed to touch the vessel while the pipet is draining
Mohr pipet
Pipet with graduation marks to the tip and is generally a blowout pipet
Serologic pipet
A pipet with a total holding volume of less than 1 mL; it may be designed as either a Mohr or a serologic pipet
Micropipet
The subgroups of measuring or graduated pipets
Mohr
Serologic
Micropipets
These pipets are designed to dispense one volume without further subdivisions
Transfer pipets
Pipet used with biologic fluids having a viscosity greater than that of water
Ostwald-Folin pipets
Pipet designed to dispense or transfer aqueous solutions and is always self-draining
Volumetric pipet
This type of pipet usually has the greatest degree of accuracy and precision and should be used when diluting standards, calibrators, or quality-control material
Volumetric pipet
Pipet without calibration marks and are used to transfer solutions or biologic fluids without consideration of a specific volume
Pasteur pipets
These pipets should not be used in any quantitative analytic techniques
Pasteur pipets
The most routinely used pipet in today’s clinical chemistry laboratory
Automatic pipet
A pipet associated with only one volume is termed
Fixed volume pipet
A pipet associated with different volume is termed
Variable pipet
Pipet that relies on a piston for creating suction to draw the sample into a disposable tip that must be changed after each use
Air-displacement pipet
Pipet that operates by moving the piston in the pipet tip or barrel, much like a hypodermic syringe
Positive-displacement pipet
Automatic pipets that obtain the liquid from a common reservoir and dispense it repeatedly
Dispensers and dilutor/dispenser pipets
The most desirable method for pipet calibration
Gravimetric Pipet Calibration
How often do we need to perform pipet calibration
Three or four times per year, or as dictated by the laboratory’s accrediting agency
Labware that looks like a wide, long, graduated pipet with a stopcock at one end
Buret
Function of buret
It is used to dispense a particular volume of liquid during a titration
Many compounds combine with water molecules to form loose chemical crystals. The compound and the associated water are called a
Hydrate
When the water of crystallization is removed from the compound, it is said to be
Anhydrous
Substances that take up water on exposure to atmospheric conditions are called
Hygroscopic
These compounds absorb enough water from the atmosphere to cause dissolution
Deliquescent substances
Closed and sealed containers that contain desiccant material may be used to store more hygroscopic substances
Dessicators
Type of balances that are currently the most popular in the clinical laboratory
Analytic and electronic balances
Balance required for the preparation of any primary standard
Analytic balances
A process in which centrifugal force is used to separate solid matter from a liquid suspension
Centrifugation
Centrifugal force depends on three variables:
Mass
Speed
Radius
The centrifugal force generated is expressed in terms of
Relative centrifugal force (RCF) or gravities (g)
A process in which uses porous material to separate solid matter from a liquid suspension
Filtration
The liquid that passes through the filter paper is called
Filtrate
The solid material trapped on the filter paper is called
Residue
Method for separating macromolecules from a solvent or smaller substances
Dialysis
Expressed as mass per unit volume of a substance
Density
Ratio of the density of a material when compared with the density of pure water at a given temperature
Specific gravity
Represents the ratio of concentrated or stock material to the total final volume of a solution and consists of the volume or weight of the concentrate plus the volume of the diluent, with the concentration units remaining the same
Dilution
Type of dilution when the laboratory scientist must decide on the total volume desired and the amount of stock to be used
Simple dilution
It is defined as multiple progressive dilutions ranging from more concentrated solutions to less concentrated solutions
Serial dilution
Dilution method used to obtain titer
Serial Dilutions
Mathematically establishes the relationship between concentration and absorbance in many photometric determinations
Beer-Lambert law (Beer’s law)
The act of obtaining a blood sample from a vein using a needle attached to a syringe or a stoppered evacuated tube
Phlebotomy, or venipuncture
The most frequent site for venipuncture
Antecubital vein of the arm
Relation of needle gauge and needle size
Inversely related; the larger the number, the smaller the needle bore and length
How to properly collect blood samples to patients with IV infusions?
Sites adjacent to IV therapy should be avoided; however, if both arms are involved in IV therapy and the IV cannot be discontinued for a short time, a site below the IV site should be sought. The initial sample drawn (5 mL) should be discarded because it is most likely contaminated with IV fluid and only subsequent sample tubes should be used for analytic purposes
The major difference between plasma and serum
Serum does not contain fibrinogen
What to do before centrifuging serum samples?
It is important that serum samples be allowed to completely clot (≈20 minutes) before being centrifuged
Does plasma samples require time to clot before centrifugation?
No
Destruction of red cells that can result in hemoglobin release
Hemolysis
First step in sample collection
Proper patient identification
Effects of prolonged tourniquet application
Causes a stasis of blood flow and an increase in hemoconcentration and anything bound to proteins or the cells
Why do we prohibit our patients to open and close their fist during phlebotomy?
It may cause an increase in potassium
Proper antiseptic for disinfecting the site when drawing blood alcohol levels
Non-alcohol antiseptics
Laboratory test often used to assess the completeness of a 24-hour urine sample
Creatinine analysis
The average adult excretes _____ of creatinine per ___ hours
1-2grams; 24hours
Is CSF an ultrafiltrate of the plasma?
Yes
Sample used to assess fetal lung maturity (L/S ratio), congenital diseases, hemolytic diseases, genetic defects, and gestational age
Amniotic fluid
Increased bilirubin pigment in blood samples
Icterus
Increased lipids in blood sample
Lipemia
Plasma or serum samples should be analyzed within
4 hours
What to do when testing of plasma or serum samples is not possible within 4 hours?
Refrigerate at 4°C for 8 hours
Temperature requirements when storing plasma or serum samples for a longer period
-20°C
