Phlebotomy Questions

Which of these patients may NOT be a candidate for capillary blood collection by dermal puncture?

-a patient who is dehydrated -It may be difficult to obtain a sufficient blood sample by dermal puncture from a patient who is dehydrated. Collecting a specimen by dermal puncture rather than by venipuncture is often the preferred method for a neonate, a severely burned patient, and an elderly patient with fragile veins.

When is capillary blood collection appropriate?

1. A heel puncture is the most indicated type of blood collection for neonates due to their small size of veins. 2. An extremely obese person may present a challenge in collecting venous blood, their veins may be too deep for the needle to reach. 3. Patients with extensive scarring on their arms may have damaged or fragile veins that should be avoided for blood collection.

Gray tube

-Additive: Sodium fluoride, and sodium or potassium oxalate -Function of additive: Fluoride inhibits glycolysis, and oxalate prevents clotting by precipitating calcium. -Common lab tests: Glucose (especially when testing will be delayed), blood alcohol, lactic acid

Green top tube

-Additive: Sodium or lithium heparin with or without gel -Function of additive: Prevents clotting by inhibiting thrombin and thromboplastin -Common lab tests: Stat and routine chemistry

The recommended finger for capillary blood collection is the index finger (finger next to the thumb).

-FALSE -The index finger is not recommended for dermal puncture because it is often more sensitive or calloused than the middle or ring fingers (the fingers that are recommended).

Errors

1. Hemoconcentration - pooling of blood at puncture site caused by prolonged application of tourniquet. 2. Microclots - small blood clots that result from inadequate mixing of specimen. 3. Mislabeling -test results reported on wrong patient. 4. Over-dilution or under-dilution of blood; wrong additive in tube- combining tube contents.

Among the most common matrix interferents in blood, which is considered to be the most preventable with precautions taken during sample collection and handling?

HEMOLYSIS

A gel barrier has not fully separated the cell layer of blood from the serum. How could this affect serum potassium and serum glucose?

Serum glucose could be falsely decreased and serum potassium could be falsely elevated.

Before attempting any venipuncture the phlebotomist should assess a vein for:

depth, direction, resilience (health) and approximate vein size (to choose the correct needle gauge).

TDM (Therapeutic Drug Monitoring)

1. The lowest level of the drug in the patient's body is called the trough level. 2. The peak for a drug is when the level of the drug in the patient's body is the highest. 3. To assess drug concentrations during the trough phase, blood should be drawn immediately before the next dose. 4. To assess peak levels, the time for drawing depends on the route of administration: Intravenous (IV): 15 - 30 minutes after injection/infusion Intramuscular (IM): 30 minutes - one hour after injection Oral: One hour after drug is taken (assumes a half-life of > two hours)

specimen type: Capillary

1. method of collection: Dermal puncture of fingertip or heel 2. common use: Infants and young children, Elderly patients with fragile veins, Severly burned patients, Point-of-care testing

specimen type: Arterial

1. method of collection: Direct puncture of artery; vascular access device 2. common use: Arterial blood gases

Lavender or pink tube

-Additive: Potassium EDTA -Function of additive: Prevents clotting by binding calcium -Common lab tests: Hematology and blood bank

Red or gold and tiger top tubes

-Additive: Serum tube with or without clot activator or gel -Function of additive: Clot activator promotes blood clotting with glass or silica particles. Gel separates serum from cells. -Common lab tests: Chemistry, serology, immunology

Light Blue Tube

-Additive: Sodium Citrate -Function of additive: Prevents blood from clotting by binding calcium -Common lab tests: Coagulation

Which of the following procedural steps should be followed when a capillary specimen for lead is collected by dermal puncture?

The patient's hands should be thoroughly washed with soap and warm water.

A two-hour glucose tolerance test consists of a total of three blood specimen collections.

A fasting blood glucose specimen is collected. After that collection, a specified amount of glucose is ingested. Blood specimens are then collected at one and two hours for a total of three blood specimens.

Which of the following devices is recommended when puncturing a finger for capillary blood collection?

A single use puncture device with a retractable needle/blade

What is capillary blood composed of?

Arterial blood, venous blood, interstitial fluid, and intracellular fluid

Which of the veins in the antecubital area should be considered only as a final alternative due to its proximity to an artery, nerves, and tendons?

Basilic

What is the greatest challenge in collecting a quality capillary blood sample?

Clotting of sample

concerns for a phlebotomist when collecting a bilirubin specimen from a neonate?

Collecting the specimen in a clear tube, forgetting to turn off the infant's UV light, and not collecting the specimen quickly due to slow blood flow, can expose the specimen to light which in turn will break down the bilirubin resulting in erroneously decreased levels of bilirubin.

Matrix Effect: Icterus

Interfering Substance: Bilirubin

Matrix Effect: Hemolysis

Interfering Substance: Hemoglobin

Where should the tourniquet be placed when assessing a vein in the hand as a venipuncture site?

One or two inches above the wrist

Which two of the following analytes may be affected as a result of patients not adequately fasting prior to blood collection?

TRIGLYCERIDES AND GLUCOSE: Fasting is recommended for 8-12 hours prior to the collection of a lipid profile where triglycerides are being determined and prior to blood collection for glucose where a fasting level is requested.

When the transport time may be prolonged for circumstances beyond the control of the laboratory, the integrity of the sample may be preserved by keeping the sample chilled during transit.

TRUE: In most cases, the practice of controlling the specimen transportation environment by employing the use of coolers and ice packs helps to preserve the sample integrity. Avoiding exposure to extremes of temperature may help to maintain the stability of the measurand of interest.

Which area(s) are acceptable to puncture on the foot of a newborn for collection of a capillary blood specimen?

The areas that can be safely punctured on the foot of an infant are either side of the heel

Which fingers should be used for dermal puncture to obtain capillary blood specimens?

The primary sites used to obtain a capillary specimen are the middle and ring fingers. The thumb is not used because it is often more calloused and has a pulse. The index finger is often very calloused and may cause more discomfort for the patient. The fifth or little finger often does not have enough fleshy pad and may lead to possible puncture of the bone.

During the capillary blood gas collection process, what is the purpose of the metal "flea?"

To mix the specimen.

A patient has an order for microhematocrit testing. Which of the following should be collected for this testing?

Two heparinized plastic capillary tubes: A minimum of two capillary tubes should be collected for testing. The tubes should be coated with an anticoagulant to prevent clotting. Plastic rather than glass should be used to prevent injury and possible exposure to bloodborne pathogens that could occur if the glass shattered.

During capillary collection from a young child, which of the following laboratory results may be falsely increased due to excessive crying?

White blood cell (WBC) count

If blood stopped flowing freely from the finger that was punctured for a capillary blood collection, which of the following actions would be appropriate?

Wipe the site with sterile gauze to dislodge the blood clot, then gently massage the finger to get blood flowing.

To assess drug concentrations during the trough phase:

blood should be drawn immediately before the next dose is given.

Reasons for hemolysis on a capillary specimen?

contamination of the specimen with alcohol from the skin, milking the site, scraping the blood instead of allowing the blood to flow in the collection container. In infant patients, there is an increase in red blood cell (RBC) fragility and increased RBC volume, which can cause hemolysis.

Which of these pieces of personal protective equipment (PPE) is always required when a dermal puncture is performed to collect a capillary blood specimen?

gloves

Holding pressure on a site immediately after removing a needle may prevent a?

hematoma (bleeding under the skin).

Which analyte may be falsely decreased due to a delay in transport time to the laboratory?

GLUCOSE

Matrix Effect: Viscosity

Interfering Substance: Protein and immunoglobulins

Matrix Effect: Lipemia

Interfering Substance: Triglycerides and chylomicrons

How will the following laboratory results be affected if a capillary specimen is tested?

Potassium, calcium, and total protein are lower in capillary specimens, where glucose is typically higher than in venous blood.

Which of these actions could contribute to the hemolysis of the sample?

Sources of hemolysis include aggressive mixing of the sample, turbulent transportation of the sample, and using too small of needle gauge relative to the size of the evacuated tube.

When performing a capillary blood collection, the laboratory may reject the specimen due to hemolysis and/or clotting of the specimen.

1. Hemolysis may occur when the alcohol on the cleansed finger is not allowed to dry completely before puncture and subsequent collection of the blood. 2. The specimen may become clotted if the blood is not mixed by inverting the container several times after the specimen is collected. The specimen may also clot if the flow of blood is too slow, delaying collection of the blood into the container and mixing with the anticoagulant. 3. Allow the blood to flow freely into the tube using gravity to help you. The puncture site should be lowered below the level of the patient's heart. Elevating the puncture site will diminish blood flow. 4. The first drop of blood should be wiped away prior to collection of specimen to prevent contamination of the specimen with tissue fluid that could interfere with testing.

Hemolysis can be caused by:

1. Incorrectly positioning the needle in the vein so that blood flows slowly into tube. 2. Pushing the plunger of a syringe during blood transfer. 3. Alcohol that is still wet on the venipuncture site. 4. Vigorously shaking the tube after blood collection.

Insufficient blood volume may cause erroneous test results and specimen rejection. When blood flow stops, it can mean several things:

1. The bevel of the needle may be pressed against the wall of the blood vessel. If this is the case, moving the needle slightly may cause blood to begin flowing again. 2. The vein may have collapsed due to the vacuum of the tube. 3. The needle may have gone all the way through the vein. Pulling the needle back slightly may cause blood to resume flowing. 4. The tube you are using may have insufficient vacuum. Try another tube.

Specimen type: Venous

1. method of collection: Direct puncture of vein by venipuncture; vascular access device 2. common use: Routine laboratory tests

A heel puncture that is performed on a small infant should not exceed what depth?

2.0 mm: Puncturing beyond 2.0 mm may result in bone damage.

What is the correct procedure when using a winged collection device (butterfly) to draw a light-blue top tube intended for a coagulation test if this is the first tube that will be collected in the draw?

Draw and discard a waste light-blue top tube before the tube that will be used for coagulation studies.

What are examples of efforts taken to maintain sample integrity during transportation to the laboratory?

Efforts to preserve the analytes of interest in a sample include minimizing the transport time, ensuring a controlled temperature that is ideal for the intended measurands, and shielding samples from direct exposure to light.

Inaccurate analyte results due to hemolysis

Extreme care should be taken in order to avoid hemolysis of the specimen. When the specimen is hemolyzed, the concentration of analytes is changed and results are inaccurate. Some falsely increased results include potassium, magnesium, iron, lactate dehydrogenase, phosphorus, ammonia, and total protein. Some of the results falsely decreased include red blood cell count, hemoglobin, and hematocrit.

A phlebotomist can use a dermal puncture to obtain a blood specimen for every laboratory test.

FALSE: This statement is false. Collecting blood using a dermal puncture is a valuable alternative to venipuncture for the phlebotomist but cannot be used for every laboratory test. The dermal puncture is the most efficient way to obtain small quantities of blood from newborns and small children, obese patients, elderly patients and patients with severe burns. Many, but not all, blood tests analyzed in the laboratory and during point-of-care testing can be done using very small amounts of blood obtained via dermal puncture. However, some tests may require a greater volume of blood than can be obtained from a dermal puncture and some test results may be compromised by exposure to the air or tissue fluid during specimen collection. In these situations, a venipuncture is required.

If blood has stopped flowing from the finger puncture site, you should repuncture the same site to re-establish the blood flow.

FALSE: This statement is false. If a second puncture is necessary, the same site should NOT be used. To re-establish the blood flow, you could try re-wiping the puncture site with sterile gauze to dislodge a clot that may have formed. Then gently massage the finger intermittently.

A phlebotomist must perform a skin puncture to obtain CAPILLARY specimens for a complete blood count (CBC), a plasma-based chemistry test, and a serum-based immunology test. The microcollection containers that will be used are lavender top containing EDTA anticoagulant, green top containing heparin anticoagulant, and gold top containing no anticoagulant. Which of the containers should be collected FIRST?

LAVENDER: When performing a capillary draw, the lavender top container is obtained first. This decreases the possibility of clots in the container which would invalidate the results of the complete blood count test. After the lavender is drawn, other containers with anticoagulants would be collected, and containers without anticoagulants would be collected last.

A lavender top microcollection container that has EDTA as an anticoagulant is used to collect a capillary hematology specimen for a complete blood count (CBC). If additional specimens are also collected with the same dermal puncture into a green top and a red top container, at what point should the lavender top for the CBC specimen be collected?

Lavender top should be the first specimen collected: For capillary blood collection from a dermal puncture, the lavender top containing EDTA should be the first specimen collected if the blood will be used for a blood count. The reason is to ensure a specimen that is free of clots that would alter a blood count. This order of draw is different from the recommended order for a venipuncture.

How may a phlebotomist help to reduce pre-analytical variability associated with sample collection?

Phlebotomists who adhere to established sample collection procedures, including minimizing tourniquet use, selecting the appropriate needle gauge, and collecting blood from an alternate arm where an IV is not being infused, all serve to minimize pre-analytical sources of error.

John is a phlebotomist collecting a capillary specimen from a geriatric patient. After completing the collection, which of the following labeling options is NOT acceptable?

Placing the tube and label in the bio-hazard transport bag at the patient's bedside: The tube has to be labeled at the patient's bedside. Placing the label in the same bio-hazard transport bag is not a safe procedure as the label can be lost.

Which of these variables related to the collection of blood may falsely increase the plasma potassium level, if the potassium sample is collected using a green-top tube?

Potassium testing results may be falsely increased due to hemolysis caused by the rupture of red blood cells (RBCs). Shaking the tube can cause hemolysis, which will falsely increase plasma potassium. Another common source of elevated potassium is potassium-EDTA anticoagulant, often used in purple-top tubes. Potassium can also be included in intravenous (IV) solutions, and may be a source of falsely increased potassium in a blood sample if the blood sample is collected above an IV site.

Which of these methods should be used to verify the identification of an infant in the nursery prior to collecting a blood specimen?

Read the name and hospital/medical record number on the identification band attached to the baby and compare both identifiers against the blood test order.

The laboratory receives red, green, and lavender top capillary specimens for testing from a nine month old patient in the pediatric wing of the hospital. This is the second day for the patient in the hospital and the same tests were performed on the previous day. A delta check is triggered when the platelet count is found to be drastically higher than the first result from the day before. All the other test results were the same. The blood was recollected and all results were the same as earlier in the day. What could be the most likely explanation for the changes in the platelet results?

The lavender specimen from the previous day was not collected first: Platelets have a tendency to accumulate at the site of the wound as part of the clotting process. It is possible that the lavender specimen from the previous day was not collected first and the platelets started accumulating at the puncture site, therefore drastically reducing the actual count.

If a patient's dermal collection site is cyanotic (bluish in color due to reduced blood circulation), how should the phlebotomist proceed?

The phlebotomist should apply a warming device, such as a heel warmer, to the site to increase blood flow.