Is the Helix Test a Batch Monitoring System? Understanding the Differences and Applications

What is the Helix Test?

The helix test, as described in standard EN ISO 11140-6 (former EN 867-5), consists of a 1.5-meter Teflon tube closed at one end with a Teflon capsule containing a biological indicator. This test was specifically developed as a type test to evaluate the technical air removal specifications of sterilizers, particularly small tabletop sterilizers according to EN 13060 Type B and large sterilizers according to EN 285.

The primary purpose of the helix test is to serve as a functional test of the sterilizer after heating up in an empty chamber. It's commonly used as a replacement for the traditional Bowie-Dick test in small tabletop sterilizers, where the original BD cotton pack is too large to fit properly.

Understanding Batch Monitoring Systems

A batch monitoring system serves a fundamentally different purpose. It's sterilized together with the actual load to verify that air removal and steam penetration are adequate to guarantee sterility of that specific load. For a monitoring system to be effective for batch monitoring, it must have more difficult air removal characteristics than the load it's meant to represent.

This is where the limitation of the helix test becomes apparent. While the helix test is valuable for its intended purposes, it can only represent a simple load with relatively easy steam penetration requirements. This makes it suitable only in exceptional cases for batch monitoring applications.

The Critical Difference

The key distinction lies in the complexity of the challenge each test presents. The helix test provides a standardized challenge that's appropriate for verifying basic sterilizer function and air removal capability. However, real-world loads often present more complex challenges, including:

• Wrapped instrument sets with multiple layers
• Complex geometric configurations
• Mixed material loads
• Hollow instruments with narrow lumens
• Dense packaging arrangements

These real-world scenarios require monitoring systems that can simulate the worst-case penetration conditions that might be encountered in actual practice.

Proper Applications of the Helix Test

The helix test should be used for:

1. Type testing of steam sterilizers to verify they meet air removal specifications
2. Start-up testing in empty sterilizer chambers, particularly in the morning before beginning daily operations
3. Functional verification of sterilizer air removal systems

When to Use Dedicated Batch Monitoring Systems

For routine batch monitoring, specialized Process Challenge Devices (PCDs) designed specifically for this purpose are essential. These systems are engineered to represent normal loads and loads with difficult air removal characteristics, ensuring safe sterilization when correctly selected to match the specific load configuration.

Modern Type 2 PCD systems according to EN ISO 11140-1 offer the versatility to be used not only in steam sterilization processes but also in low-temperature sterilization methods such as ethylene oxide (EO), low-temperature steam and formaldehyde (LTSF), or vaporized hydrogen peroxide (VHPO) processes.

Making the Right Choice

Selecting the appropriate monitoring system depends on understanding your specific sterilization process and load configuration. Using the helix test for batch monitoring when more challenging loads are being processed could create a false sense of security, as the test might pass while the actual load remains inadequately sterilized.

The construction of advanced PCD systems often involves sophisticated designs using multiple volumes connected in series, where simple measurements of length and diameter don't provide adequate information about the real penetration characteristics. Professional guidance is essential for selecting the correct monitoring system for each application.

Partnering with Mesa Labs/GKE gives you access to comprehensive sterilization monitoring solutions, expert guidance on proper test selection, and the support you need to ensure effective batch monitoring and regulatory compliance across all your sterilization processes.