- Top 5 mistakes in blood collection and sampling
- Errors in blood collection in commercial and clinical laboratories
- Introduction
- 1. Non-fasting patient – Top 5 mistakes during blood draws
- 2. In-vitro hemolysis – Top 5 mistakes during blood collection
- 3. Clotted sample – Top 5 mistakes when drawing blood
- 4. Insufficient sample volume (too small a sample) – Top 5 errors in blood collection
- 5. Delayed processing – Top 5 errors in blood collection
- FAQs about the top 5 mistakes when drawing blood
- Summary: The top 5 errors in blood collection and their impact on laboratory results
- Sources:
Top 5 mistakes in blood collection and sampling
Original article by: Linn Clarizio, DVM, Kansas State University
Lisa M. Pohlman, DVM, MS, DACVP, Kansas State University
Errors in blood collection in commercial and clinical laboratories
Introduction
Errors in veterinary laboratories – both in clinical and commercial settings – can be divided into three categories:
- Preanalytical errors: These errors occur before the actual analysis and are associated with errors in sample collection and handling. They are the most common source of error in human and veterinary laboratories.
- Analytical errors: These arise during laboratory testing and relate to factors such as the accuracy, sensitivity, and specificity of the equipment or methods used.
- Post-analytical errors: These errors occur after the analysis and are often due to faulty documentation or misinterpretation of the results.
According to the authors, the following five errors are among the most common pre-analytical problems that can lead to incorrect laboratory results.
1. Non-fasting patient – Top 5 mistakes when drawing blood
Increased Triglyceride levels, which is Lipemia Lipemia can be caused by either pathological factors or by a meal before blood collection. In most cases, it occurs as... postprandial change in patients who are not fasting (see Figs. 1 and 2).
How does lipemia affect laboratory results?
Lipemia increases the Turbidity of serum and plasma, which can distort tests that rely on light scattering, e.g.:
- Total protein levels (measured by refractometry)
- Hemoglobin levels and related indices
- Bilirubin levels
Lipid levels can also be falsely low. Electrolyte levels cause, especially if the sample is con indirect potentiometry is measured. Many analytical instruments dilute the sample before measurement, which can lead to problems with lipemic samples. Volume displacement This leads to: The high triglyceride levels displace water, thus increasing the measured concentration of Sodium, potassium and chloride appears falsely lower.
💡 Solution: The simplest method to avoid lipemia-related errors is to instruct pet owners to check their animals Fasting should be maintained for 8 to 12 hours before blood collection..
2. In vitro hemolysis – Top 5 mistakes when drawing blood
Hemolysis refers to the destruction of red blood cells, causing the plasma or serum to become pink to red discoloration assumes (see Fig. 3). Hemolysis can either pathological (in vivo) or artifact-related (in vitro) appear.
Causes of in-vitro hemolysis:
- Traumatic blood draw due to needles that are too small or strong suction with the syringe
- Improper handling such as vigorous shaking of the sample
- Extreme temperatures (e.g. direct cooling on ice or heat)
- Delayed processing the sample
Consequences of hemolysis:
- Incorrect hematology values:
- Falsely low erythrocyte count
- Incorrect hematocrit values
- Influence on biochemical tests:
- Free hemoglobin absorbs light and can interfere with enzyme tests such as Bilirubin, creatine kinase and cholesterol disturb.
- Intracellular components such as Potassium, OLD and AST are released and can cause falsely high readings.
💡 Solution:
- Gentle blood sampling with large-bore needles (e.g. 20g for dogs/cats, 18g for horses/cattle)
- Do not use strong suction with the syringe.
- Store the sample in a cool, but not frozen, place.
- Rapid analysis or prior centrifugation
3. Coagulated sample – Top 5 mistakes when drawing blood
One clotted blood sample can through long extraction time, traumatic puncture or insufficient mixing with anticoagulant arise.
Why are blood clots problematic?
- Can Blocking laboratory equipment and lead to expensive repairs
- Can incorrect platelet counts cause (pseudothrombocytopenia)
- Faulty Hematology and coagulation tests
💡 Solution:
- Rapid blood collection with a suitable cannula
- Immediately mix gently (tilt 8-10 times, do not shake!)
- Visual inspection for clots prior to analysis
4. Insufficient sample volume (sample too small) – Top 5 mistakes when drawing blood
Insufficient blood volume can lead to false lab results This can lead to problems because the ratio of anticoagulant to blood is disrupted.
Problems with an insufficient sample:
- EDTA tubes: The hypertonic EDTA draws water from the erythrocytes, which leads to incorrect results. Hematocrit values caused.
- Citrate tubes (coagulation tests): Requires an exact ratio of 1:9 (anticoagulant:blood).
- Serum tubes: If there is too little blood, serum separation may not be sufficient for all tests.
💡 Solution:
- Always to the marker fill the tube
- With Contact the laboratory if the blood sample is small.
5. Delayed processing – Top 5 mistakes when drawing blood
If blood samples are not analyzed promptly, cell morphology and chemical composition can change.
Problems caused by delayed processing:
- Erythrocyte swelling → Incorrect hematocrit values
- Glucose breakdown → Falsely low blood sugar levels
- Enzyme activity persists → Falsely elevated liver enzyme levels (ALT, AST)
- Mycoplasmas (blood parasites) can detach from erythrocytes → Missed diagnosis of infection
💡 Solution:
- Evaluate blood tests within 12 hours
- If necessary, separate serum/plasma and store at 4 °C.
FAQs about the top 5 mistakes when drawing blood
Why is it important that an animal is fasting before blood is drawn?
If an animal is not fasting, this can significantly affect blood values, especially through Lipemia – a clouding of the plasma due to elevated blood lipid levels (triglycerides).
What effect does lipemia have on laboratory results?
Electrolyte measurement errors: Lipids displace water in the plasma, causing electrolyte concentrations to appear falsely lower (e.g., sodium, potassium, chloride).
Distorted protein and hemoglobin levels: Light scattering methods used to measure total protein or hemoglobin can be disrupted by lipemia.
Effects on liver function: In particular, bilirubin tests can become unreliable.
How long should an animal fast before having blood drawn?
Dogs & Cats: 8 to 12 hours
Horses: 12 to 24 hours
Ruminants (cattle, sheep, goats): 4 to 12 hours, depending on the rate of digestion
Are there any exceptions to the fasting rule?
Yes! Some animals should not be kept on an empty stomach, e.g.:
Young, sick, or underweight animals, because they are more prone to hypoglycemia.
Diabetic animals, because a prolonged fasting period can drastically lower their blood sugar.
Emergency patients, where immediate laboratory results are required.
If blood cannot be drawn from an animal in a fasting state, the laboratory should be informed of the animal's nutritional status in order to interpret test results correctly.
How can I prevent hemolysis during blood collection?
Hemolysis, Red blood cell rupture, or the bursting of red blood cells, distorts numerous laboratory results. It can occur during blood collection or through improper handling of the sample.
Typical causes of hemolysis:
Traumatic blood draw:Using needles that are too small or applying too much suction with the syringe leads to a high negative pressure that destroys the erythrocytes.
Inappropriate handling:Vigorous shaking or excessively fast pipetting can mechanically damage the cells.
Temperature fluctuations:Direct cold (e.g., storage on ice) or heat (e.g., sunlight) can destabilize cell membranes.
Long processing delays:If the sample is not centrifuged in time, red blood cells can spontaneously break down.
Measures to prevent hemolysis:
✅ Gentle blood sampling: Use a sufficiently large needle (at least 20g for dogs/cats, 18g for horses/cattle).
✅ Avoid excessive suction with the syringe: If using a syringe, slowly pull back the plunger.
✅ Proper storage:
Do not cool directly on ice, but store in the refrigerator (4 °C).
No sunlight or excessive heat.
✅ Fast processing: If immediate analysis is not possible, centrifuge the sample and separate the plasma/serum.
Why must a blood sample be completely mixed with anticoagulant?
Anticoagulants such as EDTA, heparin or citrate They prevent blood clotting, but are only effective if they are properly mixed with the sample.
What happens if a sample is not mixed sufficiently?
Formation of microclots: Can lead to falsely low platelet counts (pseudothrombocytopenia).
Errors in blood count measurements: Clots can enclose cells, causing the cell counter to detect fewer erythrocytes and leukocytes.
Blocking of laboratory equipment: Clumps can clog pipettes or analysis tubes and cause expensive repairs.
How do you mix a sample correctly?
After removal: tube Gently tilt several times (8-10 times)., do not shake!
Prevention of coagulation: Bring samples for hematology to the laboratory immediately after blood collection.
In case of transport delays: Keep refrigerated, but do not freeze.
If a sample has clotted, it can be used for many analyses. no longer used A repeat blood test will then be necessary.
Why is a blood sample that is too small problematic?
One insufficient sample size This can lead to incorrect laboratory results because the anticoagulant-to-blood ratio is incorrect.
What happens if there is too little blood in the tube?
For EDTA tubes:The anticoagulant is hypertonic and draws water from the blood cells → altered cell morphology and incorrect hematocrit values.
For citrate tubes (coagulation tests):The anticoagulant-to-blood ratio is disrupted → incorrectly prolonged clotting times.
For serum tubes:If not enough serum can be obtained, certain tests cannot be performed.
Tips for correct blood sampling:
✅ Use the correct tube size: Always fill up to the mark.
✅ If little blood is available: Contact the laboratory to see if an alternative procedure is possible.
✅ Ensure the animal is well hydrated: Dehydrated animals often have poor blood flow.
Why is it important to process blood samples quickly?
One delayed processing This can distort many laboratory results. This is because blood cells and enzymes remain active and chemical reactions continue.
What problems arise from delayed processing?
Cell changes:Erythrocytes can swell, which leads to incorrect hematocrit and MCV values leads.
Pseudotoxic changes occur in neutrophils, which can lead to misdiagnoses.
Misinterpretations due to metabolic changes:Glucose continues to be broken down → falsely low blood sugar levels.
Enzymes (e.g., ALT, AST) can remain active → Elevated liver enzyme levels without actual liver damage.
Parasites can be lost:Mycoplasmas in cats detach from the cell surface and are no longer recognized.
How can delayed processing be avoided?
✅ Immediate processing or separate storage of serum/plasma
✅ Evaluate blood tests within 12 hours, ideally immediately.
✅ If a delay is unavoidable: Refrigerate samples (4 °C) or freeze serum/plasma.
Summary: The top 5 errors in blood collection and their impact on laboratory results
The Top 5 mistakes when drawing blood Pre-analytical errors, meaning errors that occur during blood collection or handling, are the most common cause of inaccurate test results. This summary discusses the Top 5 mistakes when drawing blood explained in detail to raise awareness among veterinarians and laboratory staff about potential problems and to improve the quality of blood samples.
1. Non-fasting patient – One of the top 5 most common mistakes when drawing blood
A patient who is not fasting can develop a Lipemia This can lead to abnormal blood readings that cloud the blood and affect several laboratory values. Tests based on light scattering, such as those measuring total protein, hemoglobin, and bilirubin, are particularly affected. Electrolyte levels may also appear falsely lower because triglycerides alter plasma volume. One of the Top 5 mistakes when drawing blood Therefore, the failure to instruct owners to keep their animals safe is... Fasting should be maintained for 8 to 12 hours before blood collection..
2. In-vitro hemolysis – A critical point among the top 5 errors in blood collection
Hemolysis occurs when red blood cells rupture and can cause abnormal potassium, liver, and enzyme levels. Among the Top 5 mistakes when drawing blood This is particularly problematic because free hemoglobin molecules can distort the test results. Causes of hemolysis include a needle that is too small, strong suction with the syringe, vigorous shaking of the sample, or temperature differences. To prevent this, Top 5 mistakes when drawing blood To avoid this, blood should be drawn gently using a suitable cannula.
3. Clotted sample – One of the top 5 avoidable errors in blood collection
Insufficient mixing with anticoagulant can lead to the formation of blood clots, which can block laboratory equipment or produce inaccurate results. This error occurs particularly frequently with EDTA or citrate tubes. Top 5 mistakes when drawing blood This includes inadequate mixing of the sample after collection. Immediate, gentle mixing by Tilt the tube 8-10 times can avoid this mistake.
4. Insufficient sample volume – An often overlooked one of the top 5 errors in blood collection
An insufficient sample volume can distort laboratory results because the ratio of blood to anticoagulant is incorrect. This leads to false coagulation tests or hematocrit values. Among the Top 5 mistakes when drawing blood This is one of the most common avoidable mistakes. Blood samples should always be up to the mark on the tube must be filled to ensure correct values.
5. Delayed processing – The last, but no less important, of the top 5 blood collection errors.
If a blood sample is not processed immediately, blood cells and chemical components can change. A delayed test can lead to false hematocrit values, lower glucose levels, or altered liver enzyme levels. Top 5 mistakes when drawing blood This also includes delayed sample processing. To avoid this error, blood samples should be processed as quickly as possible. Analyzed within 12 hours or stored at 4 °C.
Conclusion: Avoiding the top 5 blood draw errors for reliable diagnoses
The Top 5 mistakes when drawing blood These risks are avoidable if proper sample collection, handling, and processing are ensured. Many of these risks can be prevented through simple measures such as patient fasting, gentle blood collection, correct mixing with anticoagulant, sufficient sample volume, and rapid processing. Top 5 mistakes when drawing blood This can be prevented. Veterinarians and laboratory staff should avoid this. Top 5 mistakes when drawing blood be aware of this in order to improve the quality of diagnostics and ensure accurate laboratory values.
Sources:
- Stockham SL, Scott MA. Introductory concepts. In: Stockham SL, Scott MA. Fundamentals of Veterinary Clinical Pathology. 2nd ed. Blackwell Publishing; 2008:3-51.
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- Weiser G. Sample collection, processing, and analysis of laboratory service options. In: Thrall MA, Weiser G, Allison R, Campbell T, eds. Veterinary Hematology and Clinical Chemistry. 2nd ed. John Wiley & Sons; 2012:34-39.
- Stockham SL, Scott MA. Erythrocytes. In: Stockham SL, Scott MA. Fundamentals of Veterinary Clinical Pathology. 2nd ed. Blackwell Publishing; 2008:107-221.
- Weiser G. Laboratory technology for veterinary medicine. In: Thrall MA, Weiser G, Allison R, Campbell T, eds. Veterinary Hematology and Clinical Chemistry. 2nd ed. John Wiley & Sons; 2012:3-33.
- Norman EJ, Barron RC, Nash AS, Clampitt RB. Prevalence of low automated platelet counts in cats: comparison with prevalence of thrombocytopenia based on blood smear evaluation. Vet Clin Pathol. 2001;30(3):137-140.
- Riond B, Waßmuth AK, Hartnack S, Hofmann-Lehmann R, Lutz H. Effective prevention of pseudothrombocytopenia in feline blood samples with prostaglandin I2 analogue iloprost. BMC Vet Res. 2015;11:183.
- Stockham SL, Scott MA. Hemostasis. In: Stockham SL, Scott MA. Fundamentals of Veterinary Clinical Pathology. 2nd ed. Blackwell Publishing; 2008:261-321.
- Furlanello T, Tasca S, Caldin M, et al. Artifactual changes in canine blood following storage, detected using the ADVIA 120 hematology analyzer. Vet Clin Pathol. 2006;35(1):42-46.
- Bourgès-Abella NH, Geffré A, Deshuillers PL, Braun JP, Trumel C. Changes in hematology measurements in healthy and diseased dog blood stored at room temperature for 24 and 48 hours using the XT-2000iV analyzer. Vet Clin Pathol. 2014;43(1):24-35.
- Bau-Gaudreault L, Grimes CN. Effect of time and storage on toxic or pseudo-toxic change in canine neutrophils. Vet Clin Pathol. 2019;48(3):400-405.
- Harvey J. Evaluation of erythrocytes. In: Harvey J. Veterinary Hematology: A Diagnostic Guide and Color Atlas. Elsevier Saunders; 2012:88.
Recommended articles:
- Barr CA, Gianotti G, Graffeo CE, Drobatz KJ, Silverstein DC. Effect of blood collection by the push-pull technique from an indwelling catheter versus direct venipuncture on venous blood gas values before and after administration of alfaxalone or propofol in dogs. J Am Vet Med Assoc. 2017;25(10):1160-1165.
- Hanson K, Linklater A. Placing a central sampling catheter through a peripheral vein. Clinician's Brief. 2014;12(12):57-62.