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How Can the Presence of
Inappropriate Anticoagulant in
Specimen Collection Compromise
Sample Quality?
Beth Warning, MS, MLS (ASCP)CM
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Bench tech experience in hematology, hemostasis, urinalysis, toxicology, and chemistry in a large multi- system medical center
Program Director of a hospital based MT Program as well as Safety and Education Coordinator
Lab Director of Immediate Response Lab and Critical Access Lab
MLS instructor at University of Cincinnati for online and on campus students
About the Speaker
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Objectives
1. Review venous specimen
collection and tube order
of draw
2. Review the function of
common anticoagulants
3. Identify errant test results
based on inappropriate
anticoagulant use
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Pre-Analytical Errors
1999 IOM To Err is Human: Building A Safer
Health System
46-68.2% of errors in the lab are pre-analytical*
– 25% result in inappropriate patient care*
– Hospital costs are increased
• Patient management
• Recollection and repeat testing
• Lab investigation
• Consumables and supplies
Kaushik, Nitin, and Green, Sol. Pre-analytical errors: Their impact and how to minimize them. MLO, 5/2014
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Pre-Analytical Errors
Patient non –compliance
Misidentification
Labeling and clerical errors
Sample transport and storage
Inadequate specimen collection – Inadequate specimen volume/ratio of blood to
anticoagulant
– Incorrect order of draw
– Contamination by other anticoagulants
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Standard Procedures
WHO – World Health Organization
– WHO guideline on drawing blood: best practices in
phlebotomy
CLSI – Clinical Laboratory Standards Institute
– GP41-A6 Procedures for the collection of diagnostic
blood specimens by venipuncture -Approved
guideline, 2007
• Addresses the need to prevent errors in the lab induced by
additive contamination
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Order of Draw
Sterile tubes
Sodium citrate
Clot activator/SST
Lithium heparin/PST
EDTA
Sodium fluoride
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Common Anticoagulants
To provide specimens appropriate for laboratory
testing
– Sodium Citrate
– Lithium Heparin
– EDTA
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Sodium citrate
3.2% buffered Sodium citrate
– Chelates calcium
– When filled, provides a 9:1 ratio of
blood to anticoagulant
Anticoagulant of choice for
coagulation assays
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Coagulation Cascade
By Dr Graham Beards - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19094276
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Heparin
Sodium, Lithium or Ammonium salts
Binds to antithrombin to cause a conformational change – Interferes with binding to
coagulation factors XIIa, Xia, X, and Thrombin
Anticoagulant of choice for electrolytes, pH, blood gases, ionized calcium
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Coagulation Cascade
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EDTA
Potassium ethylene diamine tetra-acetic acid – K2 EDTA or K3 EDTA
– Chelates calcium and other ions
– Commonly used in hematology for morphological and quantitative properties of cellular components
– Use in Immunohematology for plasma and cellular testing in antigen and antibody detection
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Coagulation Cascade
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Errors in Collection Processes
Transfer of blood from one collection tube to another – Mixing of anticoagulants
– Changing anticoagulant to blood ratio
Out of sequence order of draw – Sample carryover from rubber septum of needle
Droplet transfer from syringe/transfer needle tip into fresh tube – Anticoagulant carryover
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Impact of Sodium Citrate
Collection Error
Not suitable for Ca2+ testing due to chelating
action of anticoagulant
Not suitable for AST and ALP testing
Incomplete fill volume
Mixing two tubes for full volume
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Impact of Heparin Collection Error
May interfere with antibody – antigen reactions,
decreasing the rate of reaction
– Inhibits DNA polymerase in PCR reactions
Insufficient quantity of blood in tube
– Fill volume 90% of recommended volume
Prolongation of PT, aPTT
False increase in Na+, BUN, or Li+ testing
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Impact of EDTA Collection Error
Not suitable for Ca2+ testing due to action of
anticoagulant
Under filling of tubes increases EDTA
concentration
If the recommended order of draw during
collection is not followed, K2EDTA salts can be
carried over
– Adverse effect on chemistry and coagulation assays
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Impact of EDTA - Coagulation
Elongated activated partial thromboplastin time
(APTT)
Elongated prothrombin time (PT)
– Lowers activity for Factors V, VIII
Reduced fibrinogen level
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Impact of EDTA - Chemistry
Not suitable for Ca2+, Zn2+
Not suitable for Alkaline Phosphatase and
Creatine kinase enzymes
– Chelation of enzymes within the reaction reagent
– Not suitable for K+, Zn2+
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Impact of EDTA – Chemistry
Due to presence of K2EDTA/ K3EDTA, see
Hyperkalemia – Potassium >5.5 mmol/L
• True increase would indicate impending cardiac arrest
Falsely elevated hypokalemic value
Most likely due to incorrect order of draw and carry over of EDTA
Identify through Delta checks, unbelievable values
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Impact of EDTA - Chemistry
Hypcalcemia
– Values <2 mmol/L
Hypomagnesium
– Values <0.7mmol/L
Hypozincemia
– Values <11µmol/L
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Impact of EDTA Contamination
~13,000 Electrolyte Profiles – 3.1% elevated K+ suggested EDTA contamination
~7300 Ca2+ assays
– 14.3 % of hypocalcemic showed contamination
~570 Mg2+ assays – 4.5 % of hypomagnesemic showed contamination
~ 300 Zn2+ assays – 1.4% hypozincemic showed contamination
92% normalized upon recollection
C.L. Sharratt, C.J. Gilbert, M.C. Cornes, C. Ford, R. Gama .The International Journal of Clinical Practice. August 2009,
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Impact of EDTA Contamination
UK study of 28,000 BUN/Lytes values
– 117 had K+ values >6.0 mmol/L
– 28 had EDTA concentrations >0.1 mmol/L
• 10 reported before identifying contamination!
– 27 that were retested were normal
Concluded that 25% of hyperkalemic lab values were
due to EDTA contamination
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Identifying EDTA Contamination
Delta check
Hyperkalemia with hypocalcemia, hypernatremia
– >6mmol/L K+
– <0.1 mmol/L Ca2+
– >155 mmol/L Na+
Assay for EDTA directly
– Analyzer
– Test strips
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Conclusion
Quality of testing is
impaired
Patient safety is
jeopardized
Incorrect presence of
anticoagulant results in
laboratory errors and
repeat testing
– Resources are wasted
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Conclusion
Tube manufacturer recommendations regarding
fill volume and mixing should be followed
Staff should be trained in proper specimen
collection, tube selection and order of draw
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References
Asivatham, J., Moses, V., Bjornson, L. Errors in Potassium Measurement: A Laboratory Perspective for the Clinician. North American Journal of Medical Sciences. 2013; 5(4):255-259
Beckman Coulter Technical Bulletin. The role of pre-analytical factors in immunoassays. Beckman Coulter, Inc. 2006.
CLSI Procedures for the handling and processing of blood specimens for common lab tests –Approved Guideline GP44-A4. Wayne, PA, 2010
CLSI Procedures for the collection of diagnostic blood specimens by venipuncture -Approved guideline. GP41-A6, Wayne, PA 2007
CLSI Tubes and additives for venous blood collection, Approved Guideline. H1-45. Wayne, PA; 2010.
Cornes, M., Ford, C., Gama, R. Spurious hyperkalemia due toe EDTA contamination:Common and not always easy to identify. Annuals of Clinical Biochemistry, 2008; 45;601-603.
Davidson, D. F. EDTA Analysis on the Roche Modular Analyzer. The Annals of Clinical Biochemistry, 2007; 44:294-296
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References Favaloro, E., Funk, D. Pre-analytical variables in coagulation testing associated with diagnostic errors in hemostasis. LabMedicine. 2012:43(2):1-10
Hackenmueller, Sarah PhD, and Straseki, Joely, PhD. Advance for Laboratory Vol 2, Issue 3, p.24. March 4, 2013
Ijaz, A., Hassan, M., Shahbax, N., Khan, I. M., Saeed, F, Tarig, K. M. EDTA Contamination in Laboratory Specimens- effect of an awareness campaign. Journal of the College of physicians and Surgeons, 2010, Vol20(6):405-407
Kaushik, Nitin, and Green, Sol. Pre-analytical errors: Their impact and how to minimize them. MLO, 5/2014
Lima-Oliveiera, G., Salvagno, G.L., Danes, E., Brocco, G., Guidi, G.C., Lippi, G. Contamination of lithium heparin blood by K2 EDTA: an experimental evaluation. Biohemica Medical, 24(3); 359-367, Oct. 2014.
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References Lima-Oliveiera, G., Salvagno, G.L, Favaloroa, E.J, Guidi, G.C., Lippi, G. Sodium Citrate Blood contamination by K2-Ethylenediaminetetratacetic acid (EDTA): impact on routine coagulation testing. International Journal of Laboratory Hematology, 37, 403-409, 2015.
Quantofix EDTA , Macherery-Nagel GmbH &Co. KG, Duren Germany. Package insert Sharratt, C.L., Gilbert, C.J., Cornes, M.C., Ford, C. , Gama, R. EDTA sample contamination is common and often undetected, putting patients at unnecessary risk of harm . The International Journal of Clinical Practice August. 2009, 63, 8, 1259-1262 Sholas, K., La’ula, S., Ence, A., Logan, H., Parker, R., Strathmann, F., Genzen, J. Evaluation of Test Strips for the Rapid Identification of EDTA Specimens, LabMedicine, 2015; 46-2; 97-108
Image:
Coagulation Cascade. Dr Graham Beards - Own work, CC BY-SA 3.0. April 2012
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