Week 5 Handout - Phlebotomy PDF

MA - 156 - Phlebotomy WEEK 5 Syringe Draws, Pre-Analytical Errors and Specimen Processing 01 SYRINGE DRAWS Patients with fragile veins may need to have blood drawn using a syringe because the stronger vacuum of the evacuated tube may collapse the vein. A small needle is usually used for the draw. Af...

MA - 156 - Phlebotomy WEEK 5 Syringe Draws, Pre-Analytical Errors and Specimen Processing 01 SYRINGE DRAWS Patients with fragile veins may need to have blood drawn using a syringe because the stronger vacuum of the evacuated tube may collapse the vein. A small needle is usually used for the draw. After the blood is drawn, the needle safety shield is activated. Blood is transferred to evacuated tubes using a blood transfer device. When using a syringe one important step is to prep the syringe, sometimes called burping the syringe. This is to ensure that the seal is broken and that the plunger will moves smoothly during collection. Pull the plunger back to break the seal on the syringe, then push the plunger forward to the hub. Like with a WIS we see a small flash of blood in the hub of the syringe, indicating that the vein has been entered. Unlike the evacuated tube, the syringe does not automatically fill with blood. Pull back the plunger evenly, gently, and slowly to withdraw the blood. Be sure to firmly brace the hand holding the barrel against the patient’s arm so that only the plunger moves. Excess pressure caused by pulling back on the plunger too quickly can cause hemolysis or the vein to collapse. Transferring the blood to evacuated tubes is done in the same order as if the evacuated tube system were used (blood culture, light blue, and so on). Rubber stoppers should not be removed. It is important to transfer blood immediately to prevent clotting of the blood in the syringe. Never transfer blood from a syringe with an exposed needle. Instead, activate the safety device on the needle, remove it from the syringe, and dispose of it according to your institution’s procedures. Then, attach a blood transfer device to the syringe. Holding the syringe upright, push the first tube up into the transfer device. Angle the tube slightly so blood flows slowly down the side of the tube, rather than dropping straight down, to prevent hemolysis. Allow the tube to fill without applying any pressure to the plunger. Pushing on the plunger causes hemolysis and increases the risk of causing an aerosol spray when the needle is removed. The evacuated tube will fill according to its vacuum capacity. If you need to fill a second tube, remove the first and insert the second tube just as you did the first. Invert all tubes to mix after removal from transfer device. 02 PRE-ANALYTICAL VARIABLES AND ERRORS There are three types of variables: pre-analytical, analytical, and post-analytical, each of which can affect test results. The phlebotomist is most responsible for controlling pre-analytical variables, those that occur before analysis of the specimen. Specimen collection accounts for more than half of the errors in pre-analytical variables. Analytic variables, those that occur during specimen analysis, can be affected by pre-analytical variables, such as collection time or transport conditions. Post-analytical variables, such as delays in reporting results or improper entry of results in the data bank, may also be part of the phlebotomist’s responsibilities. Many pre-analytical variables arise during patient preparation and specimen collection. Although not all of them can be completely controlled in every procedure, developing skill as a phlebotomist largely means minimizing the effect of these variables to the greatest extent possible. The total testing process is the entire process from ordering of a test to the interpretation of test result. It starts and ends with the patient, and can be subdivided into three phases i.e. preanalytical step, analytical step and post-analytical step. Pre-analytical Phase - This phase involves in the test request, patient and specimen identification, blood drawing sample collection, handling and the transportation of specimens to the laboratory Pre-analytical Errors - These include errors in specimen preparation which involves all activities to render a sample suitable for analysis. Log-in, centrifugation, aliquotting, pipetting,dilution, and sorting specimens into batches for their introduction into automated analyzers are all included in pre analytical errors. Most studies demonstrated that a large percentage of laboratory errors occur in the pre and post analytical phases, with fewer mistakes occurring in analytical phase. Pre-analytical errors account for 46-68% of errors in the total testing process, analytical errors account for only 7-13% of errors, and post-analytical errors account for 19-47% of errors in the total testing process. Breakdown of Pre-analytical Errors Inappropriate Laboratory Test Requisition - Many studies indicate the importance of the prepre-analytical phase. Misuse of laboratory services through requesting inappropriate laboratory test is under scrutiny worldwide because of its impact on total costs, and the inherent increased risk of medical errors and injury. The estimations of inappropriate laboratory tests vary from 11% to 70% for general biochemistry and hematology tests, 5% to 95% for urine screens and microbiology, and 17.4% to 55% for cardiac enzymes and thyroid tests. This type of error generally comes from the provider entering the incorrect test, or incomplete orders. Incomplete Laboratory Request Forms - One important source of pre-analytical error is incorrect or incomplete information on the test request or labels which have been found in more than two thirds of all rejected samples in the laboratory. Several other studies confirm that test requests can be a clinically important source of errors. Paperbased test requests are risky as they can be incompletely filled, placed in the wrong collection box, or simply be lost. Incomplete laboratory requests forms are rarely rejected at the service point and in many instances the reception staff in the laboratory may not know the significance of the missing data. Specific missing information included the physician’s name, misidentification of patient and requested tests. Wrong Patient Identification - Correct patient identification is the most important task in all medical procedures, therefore, efforts to ensure compliance with standardized identification routines should be prioritized. Mistakes in patient identification before specimen collection is responsible for up to 25% of all pre-analytical errors while, critical patient identification errors occur in approximately 1 out of 1200 test requested. Mistakes in patient identification often occur during manual tasks which can be avoided using electronic technologies like barcodes, radio-frequency identification and wristbands. Wristbands have patient’s name and identification number, and sometimes also have a barcode. Studies have reported error rates of 0.3– 11% for identification wristbands mostly comprising of missing or incomplete wristbands, and wrong wristband on the patient. Wrong Labeling of the Containers - Labeling of specimen containers should always be done immediately after sample collection while still in the presence of the patient, and after reconfirming patient identity. Labeling them after leaving the patient increases the risk of the specimen collection from the wrong patient. Mislabeling is responsible for 50% of all identification errors. Potential Outcomes of Collection Errors - Proper sample collection is an important part of good laboratory practice and improper collection can lead to delays in reporting, unnecessary re-draws/retests, decreased customer satisfaction, increased costs, incorrect diagnosis / treatment, injury and occasionally death. Prescription practices: studies have shown the importance of checking for specimen adequacy as a critical factor in test result accuracy and usefulness. Samples that are missing, coagulated, hemolysed, insufficient or wrong due to inappropriate specimen collection and handling account for a large percentage of preanalytical mistakes. Inadequate Volume - Insufficient volume is a major factor leading to rejection of samples. The main reason for this anomaly is the ignorance of the phlebotomist, difficult sampling as in pediatric patients, debilitated cases, those on chemotherapy and those with difficult to localize veins. Insufficient sample constituted the most frequent cause of test rejection in a study done in out patients department. Incorrect Phlebotomy Practices - Incorrect phlebotomy practices are also one of the main reason behind pre-analytical errors which occur due to lack of knowledge or heavy workload. Ideal phlebotomy practices should be adopted by all health care workers. Hemolysis - Hemolysis of samples occur when blood is forced through a fine needle, shaking the tubes vigorously, and centrifuging the sample specimens before clotting. Hemolysis accounts for the majority of rejections in specimen, received in the laboratory. The introduction of vacuum tubes along with the closed system of blood collection has made blood collection efficient and easy. But lack of staff training engaged in phlebotomy is an impediment for expediting sample collection and transport. Freezing and thawing of blood specimens also causes massive hemolysis. A study reported that over 95% of the hemolysed samples were due to incorrect sampling procedure or transportation. Hemolysis leads to the extravasation of intracellular contents into the plasma, leading to false high values of potassium, aspartate amino transferase (AST) and lactate dehydrogenase (LDH). Delayed Transport of Specimen - Transport delays to the laboratory can give rise to clinically important errors if transport conditions are not optimized. Errors in Specimen Preparation - The specimen preparation steps contribute to approximately 19% of the overall cost of analyzing a single specimen and are time-consuming (37% of time spent in producing result). Being infectious, manual handling of samples are a well-recognized hazard to laboratory staff. Possible consequences of few of the above mentioned pre-analytical errors can result in varying degrees of seriousness. Patient identification is probably the most important task in sample collection and error in this crucial step could have mild to life threatening consequence. Therefore, efforts to ensure compliance with standard identification procedures should be prioritized. Similarly wrong container labeling could also result in mild to sever life threatening consequence. 03 SPECIMEN PROCESSING General Guidelines for Specimen Transport Tubes with additives should be inverted gently and completely 5 to 10 times immediately after being drawn. Thorough mixing allows the additives to be evenly distributed throughout the sample. Gentle inversion minimizes hemolysis. Do not mix together blood from different containers. Do not mix contents from two underfilled tubes, even ones with the same additive. Mixing tubes changes the concentration of the blood/additive ratio, which can cause erroneous results. If there is not enough blood in a tube, reject it at the bedside and redraw the tube. Specimens must be correctly labeled. Bar code labels have become the standard throughout the healthcare system. An efficient and safe way to transport samples is in a leak-resistant bag with zip closure. Specimen bags are marked with a biohazard symbol and have a separate front pouch for requisitions to prevent contamination of the requisition should the specimen leak. Specimens transported from outside a hospital laboratory are carried in crush-resistant containers with absorbent material inside and biohazard labels outside the container. Government regulations require training for couriers who transport specimens in vehicles. Tubes should remain upright during transport. This accomplishes several purposes: it promotes complete clot formation when there is no additive present; it prevents sample contamination caused by prolonged contact with the stopper; it reduces the likelihood of aerosol formation during uncapping, as there is no residual blood clinging to the stopper; and since the clot does not form at the top of the tube, it does not have to be “rimmed,” or detached, from the tube, reducing hemolysis of the specimen. Time Constraints The quality of test results depends heavily on the time between when the sample is drawn and when it is analyzed—the longer the interval, the more likely the results will be inaccurate. Ongoing glycolysis (metabolic sugar breakdown within cells) within the specimen is a primary cause of inaccurate test results. Many different tests can be affected by glycolysis, including those for glucose, potassium, calcitonin, phosphorus, aldosterone, and a number of enzymes. As a general rule, an uncentrifuged blood sample should be delivered to the laboratory within 45 minutes of being drawn. Short turnaround time (stat) requisitions should be delivered to the laboratory immediately after being drawn. According to the Clinical and Laboratory Standards Institute (CLSI), no more than 2 hours should pass between collection and separation by centrifugation of cells from plasma or serum. Separating the cells from the plasma prevents alteration of the levels of analytes in the serum or plasma as the cells continue to metabolize. Analytes (the substances being tested) may be elevated or decreased if cells are not separated; glucose is falsely decreased, potassium is falsely increased, and lactate dehydrogenase is falsely elevated. Once separated, the specimen can be held for longer periods. The appropriate storage temperature depends on the sample type and tests ordered. A few sample types can wait longer before processing without loss of viability. Because fluoride inhibits glycolysis, glucose samples collected in gray-topped tubes can be held for 24 hours at room temperature and for 48 hours at 2°C to 8°C. In this example, centrifugation can be delayed. Whole blood specimens collected in ethylenediaminetetraacetic acid (EDTA) for complete blood counts (CBCs) are stable for 24 hours at room temperature; however, automated differentials must be performed within 6 hours of specimen collection, and blood smears made from such samples must be done within 1 hour of collection, because over time, EDTA distorts cell morphology. Temperature Considerations Temperature extremes can cause hemolysis. Samples that do not require freezing, cooling, or warming should be kept at room temperature during transport. Keeping Specimens Warm - Specimens that must be maintained at 37°C during transport and handling include cold agglutinins, cryoglobulins, and cryofibrinogen. The tubes for these specimens should be warmed using a heel-warmer packet before collection, and the sample should be transported wrapped in a heel-warmer packet as well. Heel warmers are effective up to 30 minutes. Some tests require warming of the sample in a 37°C heat block before testing. The phlebotomist should alert the laboratory staff of the arrival of a warm sample to make sure that it is held at the correct temperature until testing. Patients with certain types of blood disorders may have acquired cold agglutinins, which can cause problems with testing by automated instruments. To prevent this, the EDTA tube for a CBC must be prewarmed and kept warm. Specimens for cold agglutinin testing and cryofibrinogen must also be kept warm. Keeping Specimens at Room Temperature - Some specimens must be kept at room temperature. If the specimen is being delivered outside the facility by courier, it may be placed in an insulated container to protect it from extreme heat or cold. Follow facility protocols for placing specimens in a transport device for delivery. Keeping Specimens Cool - Chilling a specimen slows metabolic processes and keeps analytes stable during transport and handling. Samples that need to be chilled include pyruvate, ammonia, and lactic acid. A blood gas sample needs to be chilled if its delivery to the laboratory will be delayed. To chill a sample, place it in a slurry of chipped or shaved ice and water. This promotes complete contact between the sample and the ice bath. Avoid large ice cubes, as these may cause part of the sample to freeze. There are also commercially available systems that keep samples cold. Keeping Specimens Frozen - Some specimens must be kept frozen, because some analytes are stable only in extreme cold. These analytes require storage at temperature ranging from −20°C down to −70°C before testing. Examples include clotting factors and complement factors. For such samples, the plasma or serum should be frozen as soon as it is separated from the cells. Always freeze in plastic tubes that are designed for low temperatures and use labels that adhere to plastic at low temperatures. Tests that require freezing often require special equipment or reagents, and are usually sent out to a reference laboratory and must be transported frozen, using dry ice (frozen carbon dioxide). Protecting Specimens From Light Exposure to light can break down light-sensitive analytes. Bilirubin is the most common lightsensitive analyte; others include vitamin B12, carotene, folate, and urine porphyrin. To prevent light exposure, samples are collected in amber-colored microtubes, wrapped in aluminum foil, or an amber/brown biohazard bag, and placed inside a brown envelope or heavy paper bag. There are commercially available amber-colored sealable plastic bags that keep samples protected from light. Transporting Samples to the Laboratory How a sample is transported to the laboratory depends on the size of the institution and the degree of specialization within it. In many institutions, samples are hand-carried by the phlebotomist or another member of the laboratory team. Samples may be dropped off at designated areas within the hospital for transportation and delivery by the laboratory staff. This system works best when there are clear standards for documentation. A typical system uses a logbook at the drop-off and pickup area in which information about the specimen is documented. Minimum information should include the patient’s name, hospital number and room number, specimen type, date and time of delivery to the drop-off area, and name of the person depositing it. Larger hospitals may have a transportation department that is responsible for patient escort, as well as sample transport. In addition to the standard information concerning patient identification and sample type, specimens should be labeled with the laboratory as the destination. Some institutions use a pneumatic tube system, in which samples are carried in sealed plastic carriers that travel within a network of tubes. Shock-absorbing foam inserts are placed in carriers to reduce the shaking and agitation of the sample during transport. Samples are first routed to a central station and then sent on to the laboratory. Pneumatic systems are often used for the delivery of paperwork and other items but are not always appropriate for blood samples, and the laboratory must assess how well this system meets its needs. Factors may include the reliability of the system, the speed of delivery, the likelihood of specimen damage during transport, and the cost of the alternative. Samples should always be bagged in sealable plastic bags, and the bag completely sealed, before being placed in the plastic carrier. When a spill occurs within the tube system, it must be closed down for decontamination. Some larger laboratories may have self-contained motorized carriers that run on a track between departments within the laboratory for transporting specimens. There may also be tracks between different departments in the hospital to the laboratory, allowing for transport of specimens from outside of the laboratory. Samples may arrive at the laboratory from sites outside of the hospital, such as a community clinic or private physician’s office. These samples usually arrive by courier. Because of the short time allowed between collection and serum or plasma separation, the sample should be centrifuged at the collection site before transport. Samples also may arrive by overnight mail. Special containers are used to protect the sample and prevent contamination of other material during transport. Samples transported from outside the laboratory must adhere to both state and federal regulations that govern transportation of biological specimens. Processing Safety - The Occupational Safety and Health Administration (OSHA) requires personal protective equipment (PPE) to be worn during sample processing. Required equipment consists of gloves; a full-length laboratory coat, buttoned or snapped, with closed cuffs; and protective face gear, including either goggles and mask or a chin-length face shield. Central Processing - Specimens entering the laboratory are usually first handled by central processing, an area devoted to accessioning and sorting samples as they arrive. Staff will assess the acceptability of specimens upon arrival and reject any that are not acceptable. Staff must verify that each specimen is accompanied by a proper requisition, is correctly labeled, is of adequate volume for the tests required, is not clotted or hemolyzed, and has been correctly transported with regard to temperature and other conditions. The date and time of arrival are recorded, often with a time- and date-stamping machine. Alternatively, samples can be scanned in with a barcode reader, with the date and time recorded automatically in the laboratory’s information system. Each sample is marked with an accession number, a unique identifying number used for cataloging the sample in the laboratory. In addition, samples are labeled with bar codes that are read by an electronic reader, which also records the time the sample is received and stores it in the computer system. Samples are then sorted by sample type and destination within the laboratory. Central processing is also usually responsible for centrifuging samples, to separate plasma or serum from cellular elements, and for preparing aliquots, which are small portions of the specimen transferred into separate containers for distribution to a variety of laboratory departments. Before centrifuging, the stopper should remain on the sample to prevent its contamination or alteration. Cap removal releases carbon dioxide, which raises the pH and allows sample evaporation, causing increased concentration of analytes. An open tube is likely to pick up dust, sweat, powder from gloves, or other contaminants. It also creates the possibility of infectious aerosols during centrifugation. Clotting - Serum specimens must be completely clotted before centrifugation. Incompletely clotted samples continue to clot after serum separation, forming fibrin strands which interfere with testing. Plasma specimens, in contrast, can be centrifuged immediately because they have anticoagulants to prevent clotting. Complete clotting may take 30 to 45 minutes at room temperature. Samples from patients on anticoagulants, such as heparin or Coumadin (dicumarol) have longer clotting times, as do chilled specimens and those from patients with high white blood cell counts. Samples with clot activators (including serum separator tubes) clot within 30 minutes. If thrombin is used, complete clotting may occur within 5 minutes. Activators are also available that can be added to the tube after collection. Centrifuging - A centrifuge spins the sample at a very high speed, separating components based on density. Cellular elements, which are denser, move to the bottom; the less dense plasma or serum is pushed to the top. Centrifuges come in a variety of sizes, from small tabletop models designed to hold six to eight specimens to large floor models that can hold 20 or more. The most important principle of centrifuge operation is that every sample must be balanced by another of equal weight. Failure to balance the load causes the rotor of the centrifuge to spin out of center. This can damage the centrifuge and may allow it to move during operation, possibly causing it to fall off the table or move across the floor. In addition to the direct danger this poses to laboratory personnel, the resulting breakage of samples presents a biohazard. When necessary, an extra tube containing water should be added to balance an odd number of tubes. Repeated centrifugation of a specimen is not recommended because it may increase hemolysis of the sample and deterioration of analytes. Removing a Stopper - The major risk of stopper removal is formation of an aerosol, a microscopic mist of blood that forms from droplets inside the tube. Aerosols are especially likely if the tube or rim has been contaminated by blood during collection or transport. Many automated instruments allow for testing without stopper removal. In these cases, the instrument removes the sample by piercing the stopper of the tube. Careful stopper removal reduces the risk of aerosol formation. To remove a stopper, place a 4x4 inch piece of gauze over the top and pull the stopper straight up, twisting it if necessary. Do not rock it from side to side or “pop” it off. The Hemogard top is a plastic top that fits over the stopper to reduce aerosol formation and spattering. Commercial stopper removers are available as well. When removing a top from a tube, always use a safety shield to prevent blood from accidentally spattering on you and to reduce the risk from aerosols. There are two types of safety shields. A personal shield has a headband that sits on your head like a hat. It has a clear plastic visor that you pull down over your face. A workstation shield attaches to the work counter from either above or below. Its height can be adjusted to offer the best protection to the person using it. Preparing Aliquots - All tubes into which aliquots are placed should be labeled before filling and then capped before delivery to the appropriate department. Aliquots are not poured off because this may cause splashing and aerosol formation. Instead, an aliquot is removed with any one of several types of disposable pipetting systems. Aliquots may also be prepared automatically by an instrument in the laboratory. The system may include automated centrifuging and delivery of samples to testing instruments. A common task for the phlebotomist is to transfer serum or plasma to plastic transport tubes for testing at a commercial “send-out” laboratory. To prevent an identification error, you must label the transport tube before aliquoting the sample and then carefully match the patient information on the original tube with the transport tube label to be certain the aliquot is labeled correctly. SOURCE: Warekois, Robin, S. et al. Phlebotomy. Available from: Pageburstls, (5th Edition). Elsevier Health Sciences (US), 2020.