Clinical Chemistry 4: Specimen Collection, Handling, and Processing

Vocabulary flashcards covering key terms, anatomical structures, equipment, additives, and specimen quality interferents in specimen collection, handling, and processing.

Arteries

Thick-walled blood vessels that carry oxygenated blood from the heart to the tissues and withstand the pressure of ventricular contraction.

Veins

Blood vessels with thinner walls than same-size arteries that carry deoxygenated blood from the tissues to the heart and then to the lungs for oxygenation.

Capillaries

Blood vessels that are only $1$ cell thick, allowing the exchange of gases, nutrients, waste materials, and other substances between the blood and tissues.

Blood

A specialized body fluid that delivers necessary substances to body cells, comprising $5$ to $6$ liters ($7$ to $8\%$ of total body weight in adults) and consisting of $45\%$ formed elements and $55\%$ fluid portion.

Plasma

The fluid portion of blood inside the body or obtained by centrifuging whole blood collected with an anticoagulant; it contains all coagulation factors, including fibrinogen.

Serum

The liquid portion of blood obtained after uncoagulated blood is allowed to clot completely (requiring $20\,minutes$) and then centrifuged; it does not contain fibrinogen.

Whole Blood

A blood specimen collected with an anticoagulant in which the cellular (formed elements) and fluid portions are not separated.

Venipuncture

The collection of a blood specimen using the veins, which is the most commonly used method for specimen collection in clinical chemistry.

Arterial Puncture

Collection of a blood sample by puncturing the arteries.

Microcapillary Puncture

Collection of a blood sample from the periphery, particularly the capillaries.

Median Cubital Vein

The most preferred site for venipuncture because it is very big, very stable, not movable, and does not easily collapse.

Cephalic Vein

A big vein located laterally in the arm that may be used for venipuncture but is not most preferred because it is usually not stable and is very movable.

Basilic Vein

A big vein in the arm that is usually avoided for venipuncture due to its instability and proximity to nerves and arteries, risking accidental arterial or nerve puncture.

Hematoma

An area where an amount of blood has escaped from the blood vessels, causing pain and tenderness, making the site unsuitable for blood collection.

Mastectomy

The surgical removal of the entire breast tissue including axillary lymph nodes; blood collection from the same side must be avoided because the removal of lymph node filters predisposes the patient to infection.

Antiseptics

Chemical agents used on skin to prevent sepsis and inhibit the proliferation of microorganisms or normal flora prior to puncture, such as $70\%$ ethyl alcohol or $70\%$ isopropanol.

Tourniquet

A device applied $3$ to $4\,inches$ above the venipuncture site to obstruct venous blood return to the heart and distend the veins.

Needle Gauge

A measure of needle diameter where a larger gauge number corresponds to a smaller needle and smaller bore hole.

Syringe Method

A blood collection system (open or closed) used primarily for small, fragile, or damaged veins in pediatric and geriatric patients.

Evacuated Tube System

A closed blood collection system comprising a multisample needle, a needle and tube holder, and color-coded evacuated tubes.

Butterfly System

A winged infusion system designed for securing the needle during blood collection in patients with very fragile or small veins.

Anticoagulants

Chemical substances added to collection tubes that prevent blood clotting either by removing calcium (via chelation or precipitation) or by inhibiting thrombin formation.

EDTA (Ethylenediaminetetraacetic Acid)

An anticoagulant found in lavender-top tubes that prevents clotting by chelating calcium at an optimal concentration of $1.5\,mg/mL$ of blood; it is the anticoagulant of choice for hematology cell counts.

Sodium Citrate

An anticoagulant found in light blue-top tubes that prevents clotting by chelating calcium, requiring a strict $9:1$ blood-to-anticoagulant ratio for valid coagulation test results.

Heparin

A mucoitin polysulfuric acid anticoagulant in green-top tubes that accelerates antithrombin III action to neutralize thrombin; heparinized plasma is preferred for potassium determination.

Potassium Oxalate

The most widely used oxalate anticoagulant that prevents blood clotting by precipitating calcium, requiring $8$ to $10$ inversions for proper mixing.

Acid Citrate Dextrose (ACD)

A special-use anticoagulant available in formulations A and B that binds calcium and is used in blood banking to collect units of blood for transfusion.

Citrate Phosphate Dextrose (CPD)

A special-use anticoagulant that prevents clotting by binding calcium, utilized in blood banks for preserving blood collected for transfusion.

Sodium Polyanethol Sulfonate (SPS)

An anticoagulant found in yellow-top tubes that binds calcium and is used specifically for collecting blood culture specimens.

Sodium Fluoride

An antiglycolytic agent found in gray-top tubes that prevents glycolysis by inhibiting glycolytic enzymes at a concentration of $2\,mg/mL$ of blood for up to $48$ to $72\,hours$.

Clot Activators

Substances such as silica particles, Celite, or thrombin added to blood collection tubes to accelerate coagulation for rapid serum separation, requiring $5$ gentle inversions.

Thixotropic Gel Separator

An inert synthetic gel present in collection tubes that forms a physical barrier between cells and fluid (serum/plasma) upon centrifugation to prevent continued cell metabolism of analytes.

Trace Element-Free Tubes

Royal-blue stoppered collection tubes manufactured free of trace element contamination, used for toxicology, nutrient determinations, and measuring trace elements such as iron and magnesium.

Hemolysis

The breakdown or rupture of red blood cells releasing intracellular contents (such as potassium) into plasma or serum, imparting a reddish color and causing dilutional and analytical errors.

Icterus

A condition characterized by elevated bilirubin levels in serum or plasma, causing a dark yellow to greenish discoloration and spectral interference at $340\,nm$ and $500\,nm$.

Lipemia

A milky or turbid appearance of serum or plasma caused by elevated lipid levels, noted at levels of $400\,mg/dL$ ($4.6\,mmol/L$), leading to false spectrophotometric readings.