EQUIVALENCE VALIDATION OF MAS-100 SIRIUS®

ABSTRACT

The MAS-100 Sirius® is the successor of the microbial air sampler MAS-100 NT®. It is designed for reliable monitoring of viable airborne particles in cleanroom environments. In addition to validation according to ISO 14698 Annex B and EN 17141 Annex E, MBV performed additional testing to ensure comprehensive validation of the instrument's performance.

This application note is part of a series and focuses on the parameter EQUIVALENCE between the MAS-100 Sirius and its predecessor the MAS-100 NT. Results show no statistically significant differences in microbial recovery or variability, confirming the MAS-100 Sirius as a robust and equivalent successor to the MAS-100 NT.

INTRODUCTION

Reliable monitoring of airborne microbial contamination is fundamental for maintaining GMP-compliant cleanroom environments in pharmaceutical manufacturing.

To go beyond standard requirements of air sampler qualification according to ISO 14698 Annex B and EN 17141 Annex E and ensure the MAS-100 Sirius's functional reliability, MBV AG applied an extended validation strategy which was inspired by guidelines for alternative and rapid microbiological methods (ARMM), including Ph. Eur. 5.1.6, USP <1223>, and PDA Technical Report No. 33. It included the validation of the four parameters RUGGEDNESS, ROBUSTNESS, EQUIVALENCE and SPECIFICITY. Although MAS-100 Sirius is not classified as an ARMM, these guidelines offer a sound scientific basis for performance validation akin to chemical method validation per ICH Q2(R1).

The focus of this application note is the parameter EQUIVALENCE. The goal was to verify the MAS-100 Sirius's capability to replace the MAS-100 NT in routine cleanroom monitoring by demonstrating statistical similarity in microbial recovery performance.

MATERIAL & METHODS

TEST ENVIRONMENT

The study was performed in an ISO Class 8 laboratory corridor of the pharmaceutical manufacturer F. Hoffmann-La Roche AG at Kaiseraugst (Switzerland). The corridor (approximately 3m wide and 56 m long) was pre-characterized by conducting air sampling at three locations over a period of three days, with microbial concentrations ranging up to 150 CFU/m³, providing a representative and suitable environment for evaluating air sampler performance.

MATERIALS USED

• MAS-100 Sirius (100 SLPM): 3 units (Serial Nos. 220060, 220062, 220063) with matching 300x0.6mm perforated lids (ANS830352, ANS830353, ANS830354)
• MAS-100 NT® (100 SLPM): 3 units (Serial Nos. 103549, 103550, 103552) with 300x0.6 mm perforated lids
• Anemometer MAS-100 Regulus® (serial no. 18126) for “as-found” calibration
• Agar Media: 90 mm CASO + LT ICR plates (Merck KGaA, Darmstadt, article number 14605000120, batch: 207763)

STUDY DESIGN

Prior to testing, all air samplers and their respective perforated lids were thoroughly sanitized using 70% isopropanol and sterile wipes. The instruments ran in parallel. To minimize positional bias, the instruments were placed approximately one meter apart and randomly repositioned between sampling runs.

Air sampling was conducted using a flow rate of 100 SLPM (standard liters per minute) over a fixed sampling duration of 5 minutes per run, resulting in a sampled air volume of 500 liters per measurement. Each of the six instruments (three MAS-100 Sirius and three MAS-100 NT units) completed ten independent sampling runs, yielding a total of 60 data points for analysis.

To ensure accurate airflow performance, all instruments were calibrated before and after the measurement series using a MAS-100 Regulus anemometer. All calibrations were within the required acceptance criterion.

After sampling, CASO agar plates were incubated in a two-stage protocol under controlled conditions. The plates were first incubated at 20-25°C for 4 days, followed by a second incubation phase at 30-35°C for an additional 3 days. Colony forming units (CFU) were subsequently counted and recorded for statistical evaluation.

STATISTICAL ANALYSIS AND ACCEPTANCE CRITERIA

For each sampling run, CFU recovered on the agar plates were first corrected using Feller's table to account for multiple-particle impaction and then normalized to CFU per 500L of sampled air. Statistical analysis was performed using Analysis of Covariance (ANCOVA), with "Instrument” (MAS-100 Sirius versus MAS-100 NT) as the fixed factor of interest, and “Run” and “Position” as covariates to account for variability in air bioburden across time and sampling locations. A significance level of p = 0.05 was applied throughout.

To confirm the validity of the ANCOVA model assumptions as well as to check homogeneity among the two instruments, homoskedasticity was assessed using Bartlett's Test. The normality of residuals was verified using the Shapiro-Wilk test. Statistical power of the ANCOVA was calculated using MATLAB based on the methodology described by Zar (1999), enabling quantitative assessment of the ability to detect meaningful differences between instrument types.

The following predefined acceptance criteria were applied to determine equivalence between the MAS-100 Sirius and MAS-100 NT air samplers:

• No statistically significant difference in CFU recovery between instrument types (ANCOVA, p ≥ 0.05)
• No significant difference in variance between instrument types (homogeneity of variance, Bartlett's Test, p ≥ 0.05)
• A statistical power of at least 80% for the ANCOVA model

Meeting all three criteria would demonstrate that the MAS-100 Sirius performs equivalently to the MAS-100 NT in terms of both mean recovery and measurement precision under ISO Class 8 conditions.

RESULTS & DISCUSSION

The analysis of the air sampling conducted with both the MAS-100 Sirius and the MAS-100 NT demonstrated highly comparable microbial recovery. The mean colony count per 500 liters of air was 20 CFU for the MAS-100 Sirius and 22 CFU for the MAS-100 NT, indicating a negligible difference in overall performance (Figure 1). This is further supported by the results of the ANCOVA model, which showed no statistically significant difference in CFU counts between instruments (Table 1, p = 0.821), confirming that the MAS-100 Sirius delivers performance equivalent to the MAS-100 NT under real-world cleanroom conditions (Figure 1).

Figure 1: Direct comparison of the MAS-100 Sirius air sampler with its predecessor MAS-100 NT showing summarized (pooled) data (CFU/500L, mean ± SEM, N = 60).

As expected, the sampling run had a statistically significant effect on CFU counts (Table 1), reflecting the inherent variability of airborne microbial loads over time. In contrast, the position of the instruments within the corridor did not significantly influence the results, suggesting a relatively homogeneous distribution of airborne bioburden across the sampling area.

Additionally, Bartlett's Test confirmed no significant difference in variance between the two instruments (p = 0.867), supporting the conclusion that both devices exhibit consistent measurement variation, further reinforcing the homogeneity of performance.

The calculated statistical power exceeded 99%, well above the commonly accepted criterion of 80%, confirming the validity of the statistical analysis.

In conclusion, all three acceptance criteria were successfully met, demonstrating that the MAS-100 Sirius delivers equivalent microbial collection performance to the MAS-100 NT with no significant differences in sampling efficiency or result variability.

Table 1: SUMMARY OF THE ANCOVA AND POWER TESTS USED FOR COMPARING THE MAS-100 SIRIUS AND MAS-100 NT INSTRUMENTS

CONCLUSION

This EQUIVALENCE study confirms that the MAS-100 Sirius performs on par with the MAS-100 NT. Both acceptance criteria – comparable sampling efficiency and variance – were met, and the statistical analysis demonstrated robust power.

Based on these findings, the MAS-100 Sirius can be confidently adopted as a direct replacement for the MAS-100 NT in routine viable air monitoring applications within GMP-regulated environments.

ABOUT THE AUTHOR

Corina Keller, Product Manager

Corina Keller holds a master's degree in biochemistry from the University of Zurich and an MBA from the Lucerne University of Applied Sciences and Arts. She has many years of experience in product management, focusing on translating customer needs into targeted portfolio strategies and collaborating with interdisciplinary teams to develop effective solutions for microbial air monitoring in pharmaceutical cleanrooms.

ACKNOWLEDGEMENTS

We would like to thank MGP Consulting for their valuable support in the design and execution of this study.

Our sincere thanks go to F. Hoffmann-La Roche AG for the great opportunity to conduct this study at the Kaiseraugst site.

REFERENCES

• EN 17141:2020. Cleanrooms and associated controlled environments - Biocontamination control.
• ICH Q2(R1) (2005). Validation of Analytical Procedures: Text and Methodology. ICH Harmonised Tripartite Guideline.
• PDA Technical Report No. 33 (Revised 2013). Evaluation, Validation and Implementation of Alternative and Rapid Microbiological Methods. ISBN: 978-0-939459-63-6, Parenteral Drug Association, Inc.
• Ph. Eur. Chapter 5.1.6 (current edition). Alternative Methods for Control of Microbiological Quality. European Pharmacopeia.
• USP Chapter <1223> (current edition). Validation of Alternative Microbiological Methods. United States Pharmacopeia.
• Zar J.H. (1999). Biostatistical Analysis. Fourth Edition, PHIPE, Prentice Hall.

ABBREVIATIONS

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