|Year : 2022 | Volume
| Issue : 1 | Page : 32-34
Benefits and limitations of external calibration required to validate the physical parameters of an autoclave: A brief discussion from an oncology centre in eastern India
Debabrata Basu, Prokash Mondal, SK Rafikul, Sanjib Ghorai
Department of Central Sterile Supply, Tata Medical Center, Kolkata, West Bengal, India
|Date of Submission||14-Mar-2022|
|Date of Acceptance||04-Apr-2022|
|Date of Web Publication||11-Jul-2022|
Tata Medical Center, 14, Major Arterial Road (E-W), New Town, Kolkata-700 156, West Bengal
Source of Support: None, Conflict of Interest: None
Validation is a documented procedure for obtaining, recording and interpreting the data required to establish that a process will consistently comply with manufacture's predefined specification. In healthcare facility sterilizer validation is often required because continuous operations and their relevant age, the machine may give false results that compromise the sterility assurances. Because early prediction of steriliser malfunctioning is impossible, and malfunction gets detected only when it runs. The main objective of this article is to discuss about the requirement of only autoclave physical parameters calibration is how much effective without using of chemical or biological indicators and what is the drawbacks of this system. The requirement of any steriliser monitoring is to prove that the process is effective and can deliver a product that is reproducible and meets the required quality requirements. A successful load monitor always meets all the acceptance criteria of an entire load, and gives a well validated sterility assurance.
Keywords: Autoclave external validation, process drawbacks, third-party calibration cost, quality assurance, thermocouples
|How to cite this article:|
Basu D, Mondal P, Rafikul S K, Ghorai S. Benefits and limitations of external calibration required to validate the physical parameters of an autoclave: A brief discussion from an oncology centre in eastern India. J Acad Clin Microbiol 2022;24:32-4
|How to cite this URL:|
Basu D, Mondal P, Rafikul S K, Ghorai S. Benefits and limitations of external calibration required to validate the physical parameters of an autoclave: A brief discussion from an oncology centre in eastern India. J Acad Clin Microbiol [serial online] 2022 [cited 2023 Jun 5];24:32-4. Available from: https://www.jacmjournal.org/text.asp?2022/24/1/32/350318
Validation is a documented procedure for obtaining, recording and interpreting data required to establish that a process will consistently comply with manufacture's predefined specification. There is a significant difference between 'validation' and 'verification' processes. In healthcare facility sterilizer validation is often required because continuous operation and their relevant age (due to poor or old valves, probes or sensors), the machine may give false results that compromise the sterility assurances. Because early prediction of sterilizer malfunctioning is impossible, and malfunction gets detected only when it runs. During installation, the manufacturer (second party) undergoes all the validation procedures (that include installation qualification, performance qualification and operation qualification) and certifies that the autoclave passes all the quality and safety processes. Later, they check all the physical parameters periodically as a requalification test for further quality and safety purposes. However, third-party validation is sometimes required to calibrate the steriliser as an extra precaution and for various audit purposes.
On the contrary, verification testing is performed by the healthcare professionals to confirm that the validation undertaken by a third party is applicable for the specific setting. The verification testing is performed by physical, chemical and biological indicators for daily sterility assurances.
The main objective of this article is to discuss the benefits and limitations of external validation to calibrate only the physical parameters (time, temperature, pressure and vacuum level) of an autoclave for sterility assurances as per parametric release system. In Autoclave the common physical monitors are; analog and digital meters, digital printer and gauges.
To validate the physical parameters of an autoclave externally, some wired or wireless thermocouples are used to monitor them. A thermocouple is a sensor for measuring temperature and pressure in respect of time. A validated thermocouple gives accurate data by real-time monitoring. They can provide temperature and pressure data over a wide range from −20°C to +400°C and 0 bar to 5 bar, respectively. To record calibration performances, a thermometer is used to accumulate temperature data (collected from thermocouples) and send to the computer for analysing and compute the F0 values (a complete summary of time in minutes required to reach the end point sterility of a product by exposing to a certain killing agent at a certain temperature. F-value at 121°C is known as the F0 value). Although temperature accuracy of validated thermocouples should be accurate because an error of just 0.1°C measured by a faulty thermocouple will produce an error of 2.4% in the calculated F0 value.
Getting an accurate product temperature throughout an autoclave, validation can be difficult but is imperative to calculate lethality (measurement of ability of a sterilisation process to kill microorganisms within a certain time) within an autoclave cycle. To monitor temperature at various locations throughout an autoclave chamber, a planned mapping is done by using thermocouples (16–20 numbers of 'T' type PT100 elements with silicone rubber or Teflon insulation) that are connected to the chamber and jacket. Chamber mapping consists of heat distribution studies throughout the chamber for each sterilising temperature. Heat distribution studies determine whether the temperature is uniform and reproducible and also locate the cold spots inside the steriliser. The thermocouples are placed in the autoclave chamber by a separate suitable port to avoid leakage. As temperature and pressure are related, these data are verified to confirm calibration. If any change occurs (deviation between autoclave monitors and thermocouples data), the process will revalidate again.
At present, self-contained wireless thermocouples (data logger) are available that eliminate hard wired and making it more comfortable. The advantages of wireless thermocouples are as follows: it is small in size that increases versatility and precision by allowing into properly position in very near or inside the thermo pack to get accurate data during sterilisation. Closure of the sensor to the product is more reliable than the data collected during validation process.
In some hospitals in Europe, sterile products are issued based on steriliser physical parameters (chemical and biological indicators are rarely used) which are called parametric release system. Parametric release allows product to be released or issued based on process records instead of the chemical and biological indicator sterility test. This is an advantage to eliminate the routine costs associated with chemical and biological indicators with laboratory testing. However, in India and most of the other countries, the sterile products are issued after passing all the physical, chemical and biological indicator results. Because thermocouples testing for physical parameters monitoring have some limitations such as; that they cannot detect steam quality, not to detect proper air removal and steam penetration, and also the accumulation of NCG (non condensable gasses should be ≤ 3.5%) in sterilizer chamber. Furthermore survival or kill of bacterial spores are also undetected by this system. So, this method is not a full proof for sterility assurances. Furthermore, survival or kill of bacterial spores is also undetected by this system. Hence, this method is not a full-proof for sterility assurances. Moreover, this test is very expensive [Table 1], time being and not user-friendly to practice in regular cycle. Hence, releasing the sterile product only depending on autoclave critical variables is not a safe practice to achieve sterility assurance level. In our 437-bed oncology centre in eastern India, the autoclave manufacturer calibrates the autoclaves (second party) every 6-month interval where third-party validation is our yearly practice.
The requirement of any steriliser monitoring is to prove that the process is effective and can deliver a product that is reproducible and meets the required quality requirements by Good Manufacturing Practice, Good Clinical Practice and Good Laboratory Practice. A successful load monitor meets the acceptance criteria of all the parameters (by monitoring physical, chemical and biological indicators) and giving well-validated sterility assurances.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Basu D. Appropriate use of chemical indicators in the steam sterilization process: Assured sterility and economy. Infect Control Hosp Epidemiol 2019;40:831-2.
Swenson D, Wilder JA, Hancock CO. Steam sterilization validation for implementation of parametric release at a healthcare facility. Biomed Instrum Technol 2010;44:166-74.