What causes errors in blood test results?

Blood tests are a cornerstone of modern diagnostics, offering critical insights into everything from metabolic health to hormonal balance. At-home testing has revolutionized accessibility, allowing individuals to monitor their health without visiting a clinic. However, despite advancements in medical technology, errors in blood test results can still occur, whether due to sample collection issues, handling mistakes, or biological variability.

At Medimob Screenings, we prioritise accuracy and transparency. This guide explores the most common causes of blood test errors, how they affect your results, and actionable steps to ensure reliable data.

Why Do Blood Test Errors Happen?

Laboratories adhere to strict protocols to minimise inaccuracies, but certain factors, ranging from pre-analytical mishaps to biological interferences, can still compromise results. Understanding these variables helps patients and healthcare providers interpret findings correctly and take appropriate action.

1. Sample Clotting: A Leading Cause of Failed Analysis

Blood is designed to clot. It is a vital mechanism that prevents excessive bleeding after injury. However, when a collected sample clots prematurely, it becomes unusable for many laboratory tests. Clotting typically occurs due to:

• Inadequate mixing with anticoagulants (chemicals that prevent clotting in collection tubes).
• Delays in processing, allowing natural coagulation to begin before stabilization.
• Improper storage temperatures, which can accelerate clotting.

How to Prevent It:
To avoid clotting, gently invert the collection tube 8-10 times immediately after filling, ensuring thorough mixing with anticoagulants. If blood flow is slow during collection, lightly swirl the tube to maintain homogeneity. Never shake vigorously, as this can rupture blood cells.

2. Hemolysis: When Red Blood Cells Break Down Prematurely

Haemolysis (the rupture of red blood cells) releases haemoglobin and intracellular components (like potassium) into the plasma, skewing test results. This is one of the most frequent reasons labs reject samples. Common causes include:

• Excessive squeezing or "milking" of the fingertip, which damages fragile red blood cells.
• Using a lancet that’s too large or too small, leading to inefficient blood flow.
• Scraping blood off the skin rather than allowing it to drop freely into the vial.

How to Prevent It:

• Warm your hands before testing to improve blood flow.
• Massage the finger gently in a downward motion, avoiding harsh pressure.
• Let blood droplets form naturally and fall into the collection tube without scraping.

3. Insufficient Sample Volume: When There Isn’t Enough Blood to Test

Each laboratory test requires a minimum blood volume for accurate analysis. If a sample doesn’t meet the required threshold (marked by a fill line on the vial), the lab may be unable to perform all requested tests, or any at all. This issue often arises from:

• Difficulty in blood flow (e.g., due to dehydration or cold hands).
• Premature stopping (patients assume they’ve collected enough before reaching the line).
• Leaky or faulty collection tubes.

How to Prevent It:

• Hydrate well before testing to improve circulation.
• Use the provided alcohol swab to increase blood flow to the fingertip.
• Fill the vial to the indicated line, even if it takes multiple finger pricks.

4. Mislabeling or Contamination: Administrative and Handling Errors

Even a perfectly collected sample can be rendered useless if mishandled. Common mistakes include:

• Incorrect or missing patient labels, leading to sample mix-ups.
• Using expired or contaminated collection tubes, which alter blood chemistry.
• Exposure to extreme temperatures during transit (e.g., leaving samples in direct sunlight).

How to Prevent It:

• Double-check labels before submission.
• Follow storage instructions (some tests require refrigeration).
• Use prepaid, insulated return packaging to maintain sample integrity.

5. Biological Variability: How Your Body Affects Results

Even with perfect collection, some factors can still influence accuracy:

• Fasting vs. non-fasting states (glucose, triglycerides).
• Time of day (cortisol, testosterone peak in the morning).
• Recent exercise (can elevate muscle enzymes like CK).
• Medications and supplements (e.g., biotin can interfere with hormone tests).

How to Prevent It:

• Follow pre-test instructions (e.g., fasting for 12 hours before lipid tests).
• Schedule tests at consistent times for longitudinal tracking.
• Disclose all medications/supplements to your healthcare provider.

The Medimob Screenings Promise: Ensuring Accuracy

At Medimob, we mitigate errors through:

✔ Clinically validated collection kits with anti-hemolysis additives.
✔ Step-by-step video guides for proper technique.
✔ Dedicated customer support to troubleshoot collection issues.
✔ UK-accredited laboratories with stringent quality controls.

If your sample is compromised, we provide free replacements to ensure you get the insights you need.

Final Thoughts: Minimizing Errors for Reliable Results

While no testing method is 100% error-proof, understanding these common pitfalls empowers you to take an active role in your diagnostic journey. By following best practices—proper collection, correct labeling, and adherence to pre-test guidelines—you significantly enhance the reliability of your results.