Ch. 51 and 52 Blood Collections and Analysis

Chain of custody

the ability to guarantee the identity and integrity of the specimen from its collection to the reporting of test results. May be required for impaired driving arrest, drug test, or paternity test

Acceleration of clotting

The red-topped plastic tubes require the addition of a clot activator. The glass SST red-gray marble-topped tube and the plastic SST gold-topped tube have silica additives to accelerate clotting.

Centrifugation

the process that removes the clot from serum.

Aspiration of plasma

aspiration of the plasma follows centrifugation. Plasma is transferred to another tube using a disposable pipette.

Refrigeration

Certain tests like the complete blood count (CBC) require whole blood which must be refrigerated

Three-layer collection

• The primary container for the packaging should be leak-proof, and the lids of the container should be secure.

• The secondary container should be the specimen in a red biohazard bag and should be wrapped with absorbent material.

• The outer shipping container must have the identifiers with respect to the patient, sample, and the affiliated laboratories.

Tourniquet

a constricting device that is used to control blood circulation to an extremity for a certain period of time. Application of a tourniquet before withdrawing blood helps to locate the vein for venipuncture.

Evacuated tube system

Evacuated tubes come in various sizes and use color-coded tops to indicate the tube’s contents.

Tube additives

Additives are present in all vacuum tubes. Some forms of anticoagulants are present in colored plastic tubes to prevent the blood from clotting.

Preventing needle-stick injuries

• one-handed vacutainer needles

• syringe needle safety device

• push-button butterfly safety device

• needle blunting butterfly set

Responding to needle stick injuries

• examine wound for foreign material

• wash with antimicrobial soap for 10 minutes

• undergo baseline testing for BBPs

Venipuncture steps

• palpate the skin and select puncture site

• apply tourniquet

• cleanse the area with alcohol wipes

• anchor the skin and insert bevel face-up at 15 degree angle

• push the evacuated tube and fill containers

• release the tourniquet and remove the needle

Pale yellow

Additive and Its Function: SPS prevents blood from clotting and stabilizes bacterial growth

Laboratory Use: Blood or body fluid cultures

Light blue

Additive and Its Function: Sodium citrate; prevents blood from clotting by removing calcium

Laboratory Use: Coagulation testing

Royal blue

Additive and Its Function: Sodium heparin (also sodium EDTA); inhibits thrombin formation to prevent clotting

Laboratory Use: Chemistry trace elements

Red/red-gray

Laboratory Use: Serum tests; chemistry studies, blood bank, serology

Green

Additive and Its Function: Heparin (sodium/lithium/ammonium); inhibits thrombin formation to prevent clotting

Laboratory Use: Chemistry tests, STAT testing

Lavender

Additive and Its Function: EDTA; removes calcium to prevent blood from clotting and preserves blood cells

Laboratory Use: Hematology tests

Gray

Additive and Its Function: Potassium oxalate and sodium fluoride; removes calcium to prevent blood from clotting; fluoride inhibits glycolysis

Laboratory Use: Chemistry testing, especially glucose and alcohol levels

Order of collection (by color)

Yellow (sterile), light blue, red, red-gray, gold, green, light green-gray, light green, lavender, royal blue, gray

Capillary puncture

To perform a capillary puncture, the MA can use a device called a lancet. A lancet helps puncture a capillary quickly to a predetermined depth.

Micro-collection

• devices with different additives and anticoagulants.

• They contain the same additives as evacuated tubes, which are identifiable based on the colored tops.

Capillary tubes

glass tubes with an exterior protective plastic coating used for collecting blood from a dermal puncture.

Capillary puncture under 1 yr

the medial and lateral areas of the plantar surface (bottom) of the heel are the prescribed sites for puncture.

Obtaining a capillary sample

1. Wipe the first drop of blood

2. fill sampling containers

3. apply pressure with gauze when complete

Benefits of capillary puncture

Can be used to test for hemoglobin, spun hematocrit, erythrocyte sedimentation rate, prothrombin time, and thyroid stimulating hormone

Capillary puncture over venipuncture

• pediatric, older adult patients

• Obesity

• Dehydration

• Frequent glucose monitoring

• Burns or edema

Best uses of capillary puncture

• glucose testing

• hemoglobin testing

Hematocrit

a measurement of the percentage of packed red blood cells (RBCs) in a volume of blood. Measured using capillary puncture

Factors affecting hematocrit

• age

• gender

• collection technique

• geographic location

• smoking

• physiologic condition

• pathologic factors

Microhematocrit

comparing RBC volume to the total volume of the whole blood sample. Involved collection of two capillary tubes which are processed by a microhematocrit reader

Complete blood count

• hemoglobin

• hematocrit

• RBC count

• RBC indices

• WBC count and differential WBCs

• Platelet count

Mean cell volume

The average size of RBC is an index to classify anemias. Its value is obtained by dividing Hct with RBC count.

Mean corpuscular hemoglobin (MCH)

This indicates average weight of the hemoglobin in the RBC. Normal reference range is 26 to 34 picograms (pg).

Mean corpuscular hemoglobin concentration

This is a ratio of Hgb and Hct. The normal reference range is 32 to 37 g/dL.

Abnormal RBC count

• Decreases with anemic conditions

• Increases in such conditions as dehydration, polycythemia vera, severe burns, and high altitudes

Abnormal WBC count

• Increases with such conditions as pregnancy, stress, anesthesia, exercise, exposure to temperature, and after treatment with corticosteroids

• Pathologic causes that increase WBC count include bacterial infections, leukemia, appendicitis, and pneumonia

• Decreases with such conditions as viral infections, exposure to radiations, and certain drugs and chemicals

Hemoglobin and hematocrit (H and H)

Test carried out together. Values must be equal

Anemia

a condition in which the oxygen-carrying capacity of blood is below normal. It may occur in dehydration, polycythemia vera, or severe burns, as well as in those living at high altitudes.

Mean cell hemoglobin

The MCH determines the average weight of hemoglobin in the RBC.

Mean cell ratio of Hgb and Hct

the average weight of hemoglobin in comparison to cell size.

Erythrocyte sedimentation rate (ESR)

determines the rate at which erythrocytes slowly separate from plasma and settle to the bottom of a specially calibrated tube in an hour. Indication of inflammation

Abnormal Sed rates

ESR values increase in conditions such as acute and chronic infections, rheumatoid arthritis, tuberculosis, hepatitis, cancer, multiple myeloma, rheumatic fever, and lupus erythematosus.

Leukocytosis

an increase in the number of white blood cells or leukocytes due to physiologic or pathologic reasons.

• stress

• anesthesia

• exercise

• pregnancy

• extreme temps

• infection

• cancer

Leukopenia

a reduction in the number of white blood cells.

• viral infection

• radiation

• certain drugs and chemicals

Blood platelets function

initiate the process of blood coagulation, or clotting, by producing a substance that combines with calcium ions in the blood, forming thromboplastin

Prothrombin time (PT)

refers to a method that measures how well the blood clots. Especially important test for patients on blood thinners

Partial throboplastin time (PTT)

PTT in combination with PT screens hemophilia and other hereditary clotting disorders.

International normalized ratio (INR)

The INR is widely accepted to report prothrombin time rather than time in seconds.

Blood types

The two most widely used blood antigen systems are the Landsteiner (ABO) system and the Rh (D) system.

Point of care finger sticks

1. Blood glucose testing

2. Hemoglobin A1c testing

3. Cholesterol testing

4. Liver enzymes for cardiovascular diseases

5. Thyroid hormone testing

Hemoglobin A1C

The lifespan of red blood cells is 120 days. The measurement of glucose bound irreversibly to hemoglobin for a period of 60-90 days gives the average blood glucose level assessment