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Risk Analysis Example: Sterilization

While Failure Mode and Effect Analysis (FMEA) is the most common tool associated with Risk Analysis, it's not the only tool. Prospective Risk Analysis (PRA) is a very similar tool that may also be useful in Laboratories seeking to implement QC Plans following the EP23 guideline. Here, we take a healthcare study - the sterilization process in a hospital - that has been documented in the literature and examine how Risk Analysis is applied.

Sten Westgard, MS
January 2012

The end of 2011 and early 2012 was filled with news that CMS will be abandoning "Equivalent" QC and replaced it a Risk Analysis approach, following the CLSI EP23 guideline. However, while EP23 recommends using FMEA for Risk Analysis, it is only a recommmendation. Many other techniques exist for Risk Analysis. In this application, we're going to look at a technique called Prospective Risk Analysis (PRA) and examine how it is implemented in a healthcare process. We'll learn how this is similar to and different from FMEA - and get an idea of how easy or hard this technique is to use in healthcare.

The article is from the August 2011 issue of BMJ Quality and Safety:

Interest of the preliminary risk analysis method in a central sterile supply department, Niel-Laine J, Martelli N, Bonan B, Talon D, Desroches A, Prognon P, Vincent F, BMJ Qual Saf 2011 Aug;20(8)698-703..

The paper begins by describing the setting: "The Georges Pompidou European Hospital (HEGP, AP-HP, Paris) is an 814-bed university hospital. During the last 3 years, the CSSD of the hospital has performed an ongoing quality-improvement programme and obtained the ISO 9001:2000 certificate in March 2009. To improve the QAS, we have decided to conduct a first prospective risk analysis, testing a tool not freguently used in sterilisation: the Prospective Risk Analysis (PRA)."

The major difference between using FMEA and PRA, according to the article, is that "PRA is able to highlight not only already-known risks, but also those which have never happened." FMEA tends to find causes of already known consequences, while PRA can anticipate possible problems.

Where do you start?

As with FMEA, the beginning of a PRA does not sound like an exciting adventure. First, you need to create a committee. In this case, the committee needed to cover all perspectives of the process in question. The committee includes 2 hospital pharmacists, a resident pharmacist, a senior executive, a hospital worker, a surgeon, and perioperative nurse, a technical specialist, and an engineering specialist, adn was supervised by a senior pharmacist and the hospital risk manager.

This committee mapped the process and brainstormed the various potential hazardous scenarios that could occur. After that work was complete, they made the first selection of potential hazards to address.

Establish the scales for ranking

Once the most vulnerable hazard scenarios have been identified, an additional priotization must occur.

The group decided to evaluate the potential risk scenarios in three different dimensions: severity, probability, and effort. This is very similar to a FMEA risk assessment, where often the failure modes are evaluated in two dimensions, severity and occurrence.

The severity scale used by this PRA study was essentially qualitative, on a scale of S1 to S5, S5 being worst:

Severity  Scale Consequence
S1 Minor consequences No impact on the performances and safety of the system
S2 Significant consequences Deterioration of the system's performances without any impact on its safety
Light to moderate impact on the patient's care
S3 Serious consequences Important deterioration of the system's performances without any impact on its safety
Serious impact on patient's care with light but reversible consequences (ex. increased length of stay, injury without side-effects, etc.)
S4 Critical consequences Partial deterioration of the system's safety without any irreversible consequences to maintain the activity
Major impact on patient's care with serious but reversible consequences (ex. reintervention, injury with after-affects, etc.)
S5 Catastrophic consequences Very important or total deterioration of the system's safety with irreversible consequences for the activity
(ex. Death or major permanent disability)

The probablity scale was also essentially qualitative, ranking in 5 categories:

Probability Scale Frequency
P1 Highly unlikely Occurs once per year or even less frequently
P2 Unlikely Occurs between once per 6 months to once per year
P3 Possible Occurs between once per 3 months and once per 6 months
P4 Likely Occurs between once a month and once per 3 months
P5 Very likely Occurs more often than once a month

An interesting factor added to this Risk Analysis was the Effort scale. This, again is qualitative, but it adds a "practical" dimension to the mix.In effect

Effort Scale Effort Required
E0 No effort
E1 Low effort. Requires only quick action, lead time of less than 3 months
E2 Medium effort. Requires periodic action, lead time of between 3 and 12 months
E3 High effort. Requires continuos action, lead time of more than 12 months

While this dimension is intrguing, unfortunately the paper did not discuss how the Effort ranking was incorporated into the Risk Analysis. In theory, this should only matter during implementation. We would not want to downgrade the importance of a catastrophic risk that was very likely just because it would take high effort to fix.

 

Calculate the Criticality

Again, the ranking is not the end of the story. Now that each hazard has been ranked by severity and probability, the two values are "multiplied" together to generate an overall criticality. This is very similar to FMEA, when severity is often multiplied by occurrence to get the Hazard Score - what is also sometimes called the criticality. The Criticality Matrix below doesn't actually have any numerical product, but the location of the hazard on the matrix determines whether or not the hazard is important enough to be addressed.

Criticality Scale  
Index Level of Criticality Decision
C1 Acceptable The risk is low, and risk-reducing measures are not required
C2 Tolerable under control The risk may be acceptable, but further risk-reducing measures have to be performed
C3 Unacceptable Remedial actions should be introduced to reduce the criticality, or the situation should be rejected

 

Risk
Criticality
Matrix		 Index of Severity
Index of
Probability
(below)
 S1 S2 S3 S4 S5
P5 C1 C2 C3 C3 C3
P4 C1 C2 C2 C3 C3
P3 C1 C1 C2 C2 C3
P2 C1 C1 C1 C2 C2
P1
 C1 C1 C1 C1 C2

The PRA Criticality Matrix: Probability is ranked along the rows, P5 being most frequent and probable. Severity is ranked along the columns, S5 being most severe and hazardous. The Gray shading indicates the risks that are not considered acceptable.

For those used to FMEA and risk acceptability matrices, this matrix is pretty familiar. Usually, FMEA generates a numerical result, even if it is a number that is a product of two qualitative judgments. Here, there are no numbers, just relative judgments on the acceptability of the risks.

What did the project do with this matrix?

"At then end of the first ranking by specialists, 42 scenarios (30% of the initial 141 scenarios) remained with initial criticalities of level 2 or 3 (C2 or C3)."

After the Score, What next?

Getting the Criticality score is not the end point. Really, all that it does is direct you toward the most important risks. Then the real work begins - figuring out ways to reduce that risk:

"The PRA team worked on the risk-management plan and developed 28 risk-reducing actions. After their implementation and a time of 3 months' follow-up, risk scenarios rnaked C3 were resolved., but 23 scenarios remained with a C2 residual criticality. To control residual risks, specialists defined 13 safety paramenters detailed in the catalogue of safety parameters...Team members took specific follow-up actions in order to reduce the initial risks to an 'acceptable' level or a level 'tolerable under control' (C1 or C2). After the implementation of these reducing measures, specialists quoted the residual risks. For each hazardous situation that remain 'tolerable under control' (C2), safety parameters werre created. Priority actions were established based on the level of the risk ranking of the hazard encountered and the estimated effort (E0 to E3)."

Note that the Criticality Score in PRA and FMEA is calculated twice. First you calculate the criticality as the process is right now. That Criticality helps you target your improvements. Then you calculate the Criticalities after the risk-reducing actions have been completed. That is the "residual risk." When residual risks are still too high, additional actions are neccessary, either to try and control or further reduce the risk - or to pass awareness of that risk on to the next consumer of the process.

Conclusion

This study gives us valuable insights into the PRA process, which is very similar to FMEA. It's like a typical FMEA but with fewer numbers - it may feel more qualitative, but it's essentially the same ranking. In traditional FMEA, you actually multiply two numbers and the product is the criticality. But that number is just the product of two qualitative rankings, so the fact that it's a 9 instead of a C2 is not evidence of more rigor or scientific weight. You might feel better about the 9, but that's just a feeling.

The study authors noted some other limitations:

"[A] major limitation of the tool is the time required. Indeed, the complete implementation of this method took about a year and a half from the first literature review to the last objective results in terms of risk reduction. Besides, the willingness of conducting a risk-management plan must be shared by all actors involved in the system studies; the participation of each partner of the healthcare process is essential to initiate a real change in the patient care safety.

"A possible bias of the method is the composition of the PRA team. Specialists recruited should be experienced and from various disciplines. Indeed, scenarios ranking depends on their experience, their expertise of the assessed domain and their area of competence. These factors will all have an influence on results and, as a matter of fact, on the final risk mapping. However, this bias should be avoided, choosing a large number of participants. The moderator will have to lead the team all along the process to adopt a consensual assessment for each scenario."

These two issues in PRA are also found in FMEA. First, if FMEA is done properly and thoroughly, it is time-consuming. It takes a lot of time and effort to identify, rank, calculate criticality, reduce risk, and calculate criticality again for all the possible hazards and scenarios. Second, the ranking and criticality are very subjective - different people will have different rankings and criticalities for the same hazard.

PRA is a similar approach to FMEA, with similar strengths and weaknesses. For those pursuing Risk Analysis for the development of QC Plans, this is a technique to consider carefully.

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