TR 27 was revolutionary because it classified testing methods into two categories:
| Probabilistic Methods (Subjective) | Deterministic Methods (Objective) | | :--- | :--- | | Dye Ingress (Methylene blue) | Vacuum Decay | | Microbial Immersion/Ingress | High Voltage Leak Detection (HVLD) | | Bubble Emission | Pressure Decay | | Limitation: Results vary based on operator skill and time. | Advantage: Repeatable, quantifiable, automatable. | pda technical report 27 pdf
TR 27 warned that probabilistic methods often miss small leaks (5-10 µm) that can allow microbial ingress. This section is why regulators now prefer deterministic methods for final product testing. TR 27 was revolutionary because it classified testing
Your protocol’s “Acceptance Criteria” section should quote TR 27’s guidance on correlating leak size to microbial challenge. Example: “Per PDA TR 27, a dye ingress method
“Per PDA TR 27, a dye ingress method is acceptable for detecting leaks ≥ 5 µm, provided the method sensitivity is challenged with a 5 µm positive control. For smaller critical leaks (1-5 µm), a deterministic method (vacuum decay) shall be used.”
Use the TR 27 risk matrix to determine if your product requires 100% online testing (e.g., HVLD for ampoules) versus batch sampling (e.g., dye ingress for large-volume bags).
