Scientific Evaluation of Safety

Toxicological Risk Assessment (TRA) is a critical component of biological safety evaluation under the ISO 10993 framework. It provides a quantitative basis for determining whether the chemicals released from a medical device pose a health risk to patients.
 

1. The Core Methodology (ISO 10993-17)

The TRA process typically follows a structured quantitative approach:

• Identification of Extractables & Leachables (E&L): Based on ISO 10993-18 data, we identify the chemical profile of the device.

• Derivation of Safety Limits: For each identified substance, toxicologists establish a Tolerable Intake (TI) or Tolerable Exposure (TE) based on the most sensitive adverse effects observed in scientific literature.

• Calculation of Margin of Safety (MoS): The ratio of the safety limit to the worst-case patient exposure is calculated.

  • MoS = Divided Tolerable Exposure by Estimated Exposure

  • If MoS is greater than 1, the risk is generally considered acceptable.
     

2. Key Considerations in TRA

• Duration of Contact: Risk limits are adjusted based on whether the device is for limited (< 24h), prolonged (1-30 days), or permanent (> 30 days) use.

• Worst-Case Scenario: Assessments often assume that 100% of the chemicals present in the device will be absorbed by the patient, ensuring a high safety margin.

• Analytical Thresholds: Using the Analytical Evaluation Threshold (AET) to ensure that even trace amounts of potentially hazardous chemicals are not overlooked.
  
  
  
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