Pre-Analytical Errors in Medical Laboratories — Prevention Guide

Pre-analytical errors are the most common source of error in medical laboratories, accounting for 60–70% of all laboratory mistakes. Yet they are also the most preventable.

The pre-analytical phase encompasses all steps from test ordering to sample arrival in the laboratory: physician order, patient preparation, sample collection, transportation, and sample processing before analysis. Each step is a potential source of error.

Most Common Pre-Analytical Errors

At Sample Collection

• Wrong patient identification (most critical — can lead to transfusion deaths)
• Wrong tube type (e.g., EDTA instead of plain tube for chemistry)
• Incorrect sample volume (underfill or overfill)
• Haemolysis due to difficult venipuncture or rough handling
• Lipemia not flagged to clinician

During Transportation

• Temperature abuse (glucose, lactic acid, ammonia are time-sensitive)
• Delayed transport (cells consume glucose, potassium leaks from cells)
• Improper packaging (breakage, contamination)

At Sample Receipt

• Failure to check and document sample acceptability
• Accepting and processing rejected samples without documentation
• Incorrect accessioning (wrong patient or wrong test entered in LIS)

ISO 15189:2022 Requirements

• Written patient preparation instructions for all tests
• Sample collection manual available at all collection points
• Defined sample acceptance and rejection criteria
• All rejections documented with reason and action
• Monitoring of rejection rates over time