Clinical Laboratory Specimens and Blood Samples PDF

Clinical Laboratory Specimens  Sample vs. Specimen Sample is a small portion which is a true representative of the larger portion of a material or body. ‘a blood sample’ Specimen is an individual instance that represents a class....

Clinical Laboratory Specimens  Sample vs. Specimen Sample is a small portion which is a true representative of the larger portion of a material or body. ‘a blood sample’ Specimen is an individual instance that represents a class. ‘early specimens of the art of Picasso’ In medical field, specimen is a sample of a patient's fluid, tissue or other material derived from the patient used for laboratory analysis, examination or study: a urine specimen; a tissue specimen.  Types of Biological Samples Blood Urine Cerebrospinal fluid (CSF) Feces Sputum Synovial fluid Amniotic fluid Tissue  Blood Sample Blood is one of the most frequently used sample in the clinical laboratory. Knowledge of proper collection, preservation and processing of specimens is essential. A properly collected blood sample is important to quality performance in the laboratory. Food intake, medication, activity (exercise) and time of day can effect the laboratory results for blood samples. Blood can be collected from veins, arteries or capillaries.  Venous blood Collected from superficial veins on the body. The most common sample type in clinical lab. The specimen of choice for most routine lab tests. Venous blood obtained by venipuncture.  Types of Blood Specimens 1. Serum: – Clear pale yellow fluid (non fasting serum Plasma cab be cloudy) separated from clotted blood by centrifugation. – Many chemistry test performed on serum. 2. Plasma: – Clear or slightly hazy pale yellow fluid separated from cells when blood is collected Centrifuge in an anticoagulant tube centrifuged. – Contains fibrinogen while serum don’t because it has been used in clot formation. 3. Whole blood: Blood Clot – Contains both cells and plasma. Whole Blood – Must be collected in anticoagulant tube to Serum prevent clotting. – Used for most hematology tests and many point-of-care-testing, eg. glucose meters.  Arterial Blood Blood collected from arteries, used mainly for analysis of blood gas or Arterial Blood Gases (ABG): – Partial pressure of oxygen (PaO2) – Partial pressure of carbon dioxide (PaCO2) – pH Arterial Blood and Venous blo Require special training and performed by doctors or specially trained technicians only. Usually collected from: – Radial artery – Branchial artery Heparinized syringe used in artery puncture. The drawn blood sample must be transported to the lab in ice as soon as possible not to lose any of the gashouse components.  Capillary Blood Obtained by skin puncture with a special lancet. Only small blood volume collected Used to collect blood from infants and emergency situations. Collection sites: – Tip of a finger - Adults – Heel or big toe- Infants – Ear-lobe - infants  Phlebotomy Phlebotomy means “ to cut vein” is a procedure used to collect blood from veins. Two main phlebotomy procedures: – Venipuncture; blood is collected by needle inserted into a vein. – Capillary puncture; blood collected by skin puncture made with lancet or similar device. Venipuncture is the most common method of obtaining blood for routine laboratory analysis. It is safe and quick way to obtain a large sample of blood. Must be performed by trained personnel in phlebotomy techniques; laboratory technologist, laboratory technician, physicians and nursing staff, however, phlebotomist have been specifically trained for this blood collection technique.  Patient Interaction Phlebotomy is possibly the only patient contact with clinical laboratory. Blood collection personnel must project a professional image, in terms of appearance, positive attitude and communication skills. Appearance: – First impression is important for future communication. – Lab coat should protect underneath clothes – Shoes should be conservative and clean – Long hair pull back, no long nails etc. Integrity, being sensitive to patients need and willing to offer reassurance, dependability (able to be relied upon).  Patient Interaction Communication skills – Be good listener to the patient and use the feed back to positive communication – Use easily understood verbal language – Observe patients nonverbal feeling and respond positively Family members can help to calm the patient (especially children) or increase anxiety, ask them to leave the room if necessary. Patient consent is necessary to be obtained before the procedure. Apply standard safety precautions and always wear PPE (personal protective equipment) that include ; lab coat or gowns, and gloves must be worn all the time. Use proper hand hygiene procedure to prevent spread of infections. Maintain patient confidentiality  Venipuncture Site Major veins for venipuncture are in the antecubital fossa; the area of the arm in front the elbow. – Median Cubital Vein; first choice. – Cephalic vein; is the second choice. – Basilic Vein; should not be used. Other veins; include veins in the back of hand and wrist; dorsal metacarpal veins. Leg, ankle, and foot veins sometimes used but needs permission from the physician due to potential medical complications.  Venipuncture Equipment Venipuncture can be performed on three basic methods: – Evacuated tube system (ETS) – Needle and syringe Evacuated tube system (ETS) – Winged infusing set (butterfly) ETS is the preferred method because the collected blood goes directly into the tube minimizing contamination. Needle and syringe used for small, Needle and fragile or damaged veins. syringe Winged infusing set (butterfly) used in infants children hand veins and other difficult draw situations. Winged infusing set (butterfly)  Venipuncture Equipment Tourniquet Tourniquet: rubber band applied on the patients arm to restrict venous blood flow to make veins larger and easier to find. Needle: sterile, disposable, sized by length and gauge. Needle length selection depends on the veins depth and user preference. Gauge is a number of needle diameter. Gauge and bore are inversely related, the larger the gauge the smaller the bore. Gauge selected size, depend on the condition of the vein and amount of blood required. 21 gauge is the standard size for routine venipuncture. Appropriate gauge size is important, if needle too large (small gauge) will damage the vein, if too needle too small (high gauge) sample may be hemolyzed.  Evacuated tube system Has three basic components; – Multisampling needle; allow collection of multiple samples Multisampling – The tube needle end covered by a rubber Tube holder needle sleeve to prevent blood leakage. – Tube holder: a plastic cylinder with small opening for the needle and large opening for the evacuated tube. – Various types of evacuated tubes; Have premeasured vacuum automatically fill the tube. – Vacuum loos may occur if the tube do not stored properly, opened, dropped. Or advance too far by the needle before the blood flow during venipuncture. Various types of – Tube stoppers are color coded to identify evacuated or vacuum the type of additive. tubes  Syringe system Syringe needle are available in a wide range of gauges and lengths For venipuncture 21-23-gauge. They have barrel with graduated markings and in mLs or cc (cubic centimeter) and a plunger fits into it. The plunger should be slowly pulled back to create a vacuum that pulls blood into the barrel, pulling the plunger so fast may lead to sample hemolysis.  Butterfly system A short needle with a plastic part resembling butterfly wings and a length of tubing with a luer fitting for syringe or ETS use. They came with various gauges but 23-gauge is most commonly used for phlebotomy. Smaller needles increased the risk for specimen hemolysis.  Performing a Venipuncture Using A Winged Collection Set (A) Attach tube holder or syringe to collection set (B) Remove shield and insert needle into vein by grasping wings together or holding body of device (C) Observe “flash” of blood behind “wings” (D) When blood collection is complete, activate safety feature while needle is still in vein by depressing button with index finger (E) Apply pressure to venipuncture site (F) Confirm that needle is retracted (G) Discard entire set into sharps disposal container Material needed to Perform Venipuncture Collect all the equipment needed for the procedure and place it within safe and easy reach on a tray or trolley. The required equipment are: – Safety needle or syringe or a winged collection set with tubing or evacuated tube collection system. – Evacuated blood collecting tubes – Alcohol swabs or sterile gauze – Tourniquet – Gauze or cotton – Gloves – Small adhesive bandage Venipuncture Procedure Using ETS Identify and prepare the patient – Check that the laboratory form matches the patient's identity (match the patient's details with the laboratory form to ensure accurate identification). – Make the patient feel comfortable. Inspect both arms to select the most suitable puncture site with best obvious veins. A tourniquet is applied to the arm to make the veins more prominent or distended, should be just tight enough to block venous return but not restrict arterial blood flow.  Find the Venipuncture Site The veins most frequently used are the median cubital vein and cephalic vein. The basilic vein should not be used. Under the basilic vein runs an artery and a nerve so puncturing here runs the risk of damaging the nerve or artery and is usually more painful. Palpate the vein by gently pressing the fingertip along the vein to determine its direction and estimate its size and depth.  Tube Additives Common vacuum tube additives include: – Anticoagulants; prevent blood from clotting include; ethylenediaminetetraacetic acid (EDTA), citrate, heparin, and oxalate. – Antiglycolytic agent; such as sodium fluoride to prevent blood glucose cellular consumption by glycolysis often combined with potassium oxalate. – Clot activators; coagulation factors such as thrombin and substances like glass (silica) particles or clay like diatomite that enhance clotting. – Thixotropic gel separator; during centrifugation the gel separates cells from serum or plasma. For additive optimal function if the tube should be filled to its stated volume and mixed immediately after collection by gentle inversion to mix the anticoagulant. Shaking or vigorous mixing can hemolyze the sample. Additive reliability guaranteed until the expiration date. Common tube additives and Stopper color codes  Order of Tube Draw Contaminat Special sequence of tube ing Test Potentially affected additive collection must be followed to Citrate Alkaline reduce the risk of specimen Phosphatase, contamination by Calcium and Phosphorus microorganisms or additives EDTA Calcium, Alkaline carry over that affect some Phosphatase, tests. Creatine Kinase, Potassium, Iron EDTA carry over causes the and Sodium highest problems than other Heparin Activated clotting time additives. Acid phosphatase Heparin causes the lowest Partial thromboplastin problems because naturally Protime present anti-coagulant. Oxalate Acid Phosphatase Alkaline phosphatase Amylase Order of tube draw  Performing a Venipuncture Using A Syringe (A) Cleanse puncture site, anchor vein and insert needle. (B) hold syringe with one hand while pulling back on plunger with the other hand (C) Release tourniquet and (D) Apply pressure to site immediately after removing needle Using a needleless transfer device to transfer blood from syringe to blood collection tube: (A) Attach transfer device to lock of syringe; (B) Push collecting tube into  Troubleshooting failed venipuncture Common causes of blood draw failure: – Tube position/misaligned tube in the holder; verify tube properly seated in the holder, make sure the needle penetrated the tube stopper reseat if necessary. – Loss of tube vacuum; tube may lost the vacuum before or during the draw, change new one if necessary. – Improper position of the needle in the vein; Bevel against the vein wall: remove the tube, retract the needle slightly, rotate the bevel slightly. Needle too deep: withdraw needle slightly to establish blood flow, stop the draw if hematoma forms. Troubleshooting failed venipuncture  Troubleshooting failed venipuncture Needle not deep enough: this may cause slow blood flow, gently advance the needle to establish correct flow. Needle beside the vein: withdraw the needle slightly, anchor the vein and redirect the needle into it. If redirection not successful stop and choose new site. Collapsed vein: if tube vacuum to great, syringe plunger pulled to quickly, tourniquet too tight or close to the site, the vein may collapse and stop blood flow. In elderly or fragile veins the blood flow may stop after the tourniquet release may be due to changed needle position but not vein collapse. Undetermined needle position: withdraw the needle until just under the skin palpate the arm above the needle site locate and anchor the vein and redirect the needle into it. If the vein cannot be located discontinue the draw, its painful and can damage nerves and puncture arteries.  Multiple venipuncture attempts If not possible to draw blood from the first attempt, try aging below the first site in the other arm. If the second attempt unsuccessful ask some one else to take over. If second person unsuccessful two attempts, give the patient a rest and try later. If the specimen not obtained notify the nurse or physician.  Pediatric venipuncture Ideally performed with a 23 gauge butterfly and tube holder, this allow flexibility it the child move. Infant and children has small blood volume and effort must be made to collect only the minimum amount of blood required for testing. Physical restrain may be needed for toddlers or small children to support steady the venipuncture Seated adult arm. restraining a toddler  Procedural Errors Risk Hematoma formation; rapid swelling at the venipuncture site due blood leaking into the tissue. Common causes: – Small or fragile vein – Partially inserted needle – Needle penetrate all the way through the vein – Needle removed before the torniquet release – Inadequate pressure on the venipuncture site Hematoma from Inadvertent arterial puncture; accidently sticking venipuncture an artery instead of a vein, arterial blood is collected. Infection of the site of venipuncture Nerve injury; mainly due to poor site selection or deep needle insertion to quickly, patient movement, excessive or lateral needle redirection, Nerve injury may lead to excessive pain, burning or electrical shock sensation, arm numbness, pain radiation down the arm require immediate removal of the needle.  Complications Allergies to supplies or equipment; patient can be allergic to antiseptics e.g. iodine adhesive glue bands, latex from gloves. Excessive bleeding; for example in case of hemophilia patients or patients with low platelets count. apply pressure on the site until bleeding stops, if continue beyond five minutes notify the physician. Fainting (syncope); vasovagal syncope or attack may occur suddenly, discontinue blood collection immediately. Nausea vomiting Pain; sever pain indicate sticking a nerve involvement. Petechiae; appear in some individuals as tiny red spots on the arm due to long torniquets application. Seizures and convulsions; discontinue blood collection immediately.  Analytical Issues Two conditions that may occur due to improper phlebotomy; Hemolysis; destruction (lysis) of red blood cells. Greatly affect results for potassium, magnesium, enzymes and bilirubin. Causes: Too small needle (higher-gauge). Fast plunger pulling in syringe system. Slowing of blood flow into the collection tube due to incorrect positioning of the needle in the vein. Vigorous sample mixing shaking. Hemoconcentration; high blood cellular component compared to the fluid in the sample. Can cause falsely elevated glucose, potassium, and cholesterol. Causes:  Capillary Puncture Capillary puncture; collecting blood sample from capillaries. Used to collect blood when: a) Limited sample volume e.g. in infants and pediatric patients b) Repeated venipunctures have caused severe vein damage c) Burns or bandaged areas- veins are not available for venipuncture d) For neonatal screening and molecular genetics testing Capillary blood used in compact analyzers that require only small quantities of blood for testing. Compact analyzers used for point-of-care (POC) testing, such as at the bedside, in the emergency room or in the physician’s office laboratory (POL) to perform several tests. Capillary blood is used to; – Measure hemoglobin – Perform a WBC count – Make thick and thin blood smears  Capillary Puncture Site For adults and children over the age of 2 years, the usual site for capillary puncture is the ring fingertip, because it is less hard. Thumb or index finger are the most sensitive fingers for capillary Adults and young Children puncture. For newborns (0 -2 months), infants (