Pre-analytical Laboratory Errors
Pre-analytical Laboratory Errors
By: Tim Guirl MT (ASCP)
Phlebotomy Instructor
North Seattle Community College
Health & Human Services Division
Objectives
* Identify the significant pre-analytical errors that can occur during blood specimen collection and transport
* Explain the various means of pre-analytical error prevention
* List proactive steps to reduce potential pre-analytical errors associated with blood collection and transport
Introduction
* Three phases of laboratory testing: pre-analytical, analytical and post-analytical
* Pre-analytical—specimen collection, transport and processing
* Analytical—testing
* Post-analytical—testing results transmission, interpretation, follow-up, retesting.
Phlebotomy Errors
* Phlebotomy is a highly complex skill requiring expert knowledge, dexterity and critical judgment
* It is estimated that one billion venipunctures are performed annually in the U.S.
* Phlebotomy errors may cause harm to patients or result in needlestick injury to the phlebotomist
Pre-analytical errors
* Pre- and post-analytical errors are estimated to constitute 90% of errors
* Errors at any stage of the collection, testing and reporting process can potentially lead to a serious patient misdiagnosis
* Errors during the collection process are not inevitable and can be prevented with a diligent application of quality control, continuing education and effective collection systems
Types of Collection Errors
* Patient Identification
* Phlebotomy Technique
* Test Collection Procedures
* Specimen Transport
* Specimen Processing
Patient Identification Errors
* Errors in correctly identifying the patient are indefensible
* Reasons for patient identification errors
o Proper positive patient identification procedures not followed
+ Patient identification from identification bracelet (inpatients)
+ Patient identification by asking patients to state or spell their full name (inpatients/outpatients)
+ Patient identification by staff or family member if patient unable to identify him/herself
Patient Identification Errors
o Specimen tubes unlabeled
+ Requisition or collection tube labels not affixed to tubes
# Requisition or collection tube labels in bag containing collection tubes
# Requisition or collection tube labels rubber-banded to tubes
# Collection tube labels not affixed to all tubes
# Specimen collection tubes labeled insufficiently with at minimum patient’s full name, date/time of collection, phlebotomist’s initials
Patient Identification Errors
* Collection tubes labeled with the wrong patient
o Wrong computerized labels affixed to collection tubes at bedside
o Collection tubes not labeled at the time of collection
o Collection tubes incorrectly labeled by someone other than the phlebotomist who collects the specimen
Patient Complications
* Some patient variables that affect blood specimens
o Diet
+ Fasting
o Exercise
o Obesity
o Allergies to alcohol or iodine used to clean venipuncture site
+ Use alternative cleanser such as chlorhexidine
Phlebotomy Technique Errors
* Phlebotomy technique is important
o Ensures test result validity
o Minimizes trauma to patient
o Minimizes potential for phlebotomist injury
o Reduces recollections
* Vein selection essential for successful venipuncture
o Three veins in antecubital fossa in order of selection (1) median cubital (2) cephalic (3) basilic
Phlebotomy Technique Errors
* Site Selection
o Avoid sites with IV
+ Use alternative arm or draw below IV to avoid contamination/dilution from IV
+ Document arm if IV
o Mastectomy—avoid site due to lymphostasis
+ Infection risk/alteration in body fluids and blood analytes
o Edematous areas —avoid due to accumulation of body fluids
+ Possible contamination/dilution of specimen
Phlebotomy Technique Errors
o Venous Access Difficulties
+ Obstructed, hardened, scarred veins
+ Veins difficult to locate
+ Use of Alternative sites
# Top of hand/Side of wrist
# Areas to avoid
o Vein Collapse
+ Use of appropriate needle size
+ Smaller evacuated collection tube
Phlebotomy Technique Errors
* Tourniquet Application
o Tourniquet tied too close to the venipuncture site can cause hematoma
o Veins may not become prominent if tourniquet is tied too high (more than 3 to 4 inches above venipuncture site)
o Tourniquet left on longer than one minute can result in hemoconcentration, affecting some test results
+ Tourniquet should be released as soon as needle is in the lumen of the vein and blood flow established
Phlebotomy Technique Errors
* Cleansing of venipuncture site
o Thorough cleaning with alcohol
o Allow alcohol to dry completely to avoid stinging sensation upon needle entry and hemolysis of sample
o Samples such as blood cultures should be collected using iodine to cleanse site to ensure sterility of sample
+ Recollection rate for blood cultures ranges due to contamination is as high as 50% in hospitals with increased costs, patient overtreatment
Phlebotomy Technique Errors
* Correct collection system
o Evacuated tube system (Vacutainer) for large veins in antecubital fossa
o Syringe for small, fragile veins or veins outside antecubital fossa
* Venous access
o Needle entry should be at 15 to 30 degrees depending on depth of vein
o Needle entry should be in same direction as vein, centered over vein
o Anchor vein to prevent movement during needle entry and to reduce pain to patient
Test Collection Errors
* Order of Draw
o Order of draw affects the quality of the sample and can lead to erroneous test results due to contamination with the additive from the previous blood collection tube
* Hemolysis
o Blood collected insufficient to amount of additive in tube,
o Traumatic venipuncture
o Blood collected from area with hematoma
o Vigorous shaking of tubes after collection
o Milking the site when collecting capillary samples and blood collected using a small diameter needle.
Test Collection Errors
* Timing of Collection
o Timed Draws
o Therapeutic Drug Monitoring
+ Peak and trough collection times
o Basal State Collections
+ Fasting requirements—no food or liquid except water
o Specimens affected by time of day, for example, cortisol
Test Collection Errors
* Improper collection tube drawn for test ordered
* Collection tube not completely filled
o Example—light blue top tube for Coagulation Studies. Incomplete filling results in specimen dilution and erroneous Prothrombin and aPTT test results.
Test Collection Errors
* Capillary Collections—finger stick or heel stick
o Appropriate site
+ Heel stick—sides of the bottom surface of the heel
+ Finger stick—third or fourth fingers, perpendicular to fingerprint lines on fleshy pads on finger surface
o Warming—Warm before collection to increase capillary blood flow near skin surface
o Cleaning—cleanse site with alcohol and allow to air dry
Capillary Collections
o Massaging site to increase blood flow
+ Milking site can cause hemolysis or tissue fluid contamination
+ Finger sticks—roll fingers toward fingertip at 1st finger joint several times
+ Heel sticks—gently squeeze infant’s heel before performing puncture.
o Perform puncture while firmly squeezing finger or heel
o Wipe away first two drops of blood
+ Ensure that full blood drop wells up each time
Capillary Collections
o Avoid touching capillary collection tube or micro collection tube to skin or scraping skin surface
+ Contaminates puncture site
+ Blood may become hemolyzed
o Mixing micro collection tubes with additive frequently to avoid micro clots
o Collecting tubes with additives first
o Protecting tubes for bilirubin from light
Blood Specimen Transport Errors
* Transport of blood specimens in the proper manner after collection ensures the quality of the sample
* Timing
o Some specimens must be transported immediately after collection, for example Arterial Blood Gases.
o Specimens for serum or plasma chemistry testing should be centrifuged and separated within two hours
Transport Errors
* Temperature
o Specimens must be transported at the appropriate temperature for the required test
+ On ice—ABGs, Ammonia
+ Warmed --98.6 degrees (37 C), cryoglobulins
+ Avoid temperature extremes if transported from via vehicle from other collection site
* Transport Container
o Some samples need to be protected from light, for example, bilirubin
o Transport in leak-proof plastic bags in lockable rigid containers
Error Prevention
* Phlebotomy Education
o Phlebotomists should have completed a standard academic course in phlebotomy and undergo thorough on-the-job training under the supervision of a senior phlebotomist
* Continuing Education
o Phlebotomists should participate in regular educational competency assessments (written and observational)
o Professional Licensure
* Phlebotomy Staffing
o Adequate staffing to maintain collection standards
* Technology
o Use of barcode scanners for patient identification
Questions and Discussion
* How are pre-analytical errors prevented in your laboratory?
* What technology do you use to prevent human error?
* What systems does your hospital use to prevent errors by non-laboratory staff collecting blood?
* What pro-active improvements would reduce the number of pre-analytical errors?
Pre-analytical Laboratory Errors.ppt
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