If you’ve read the ISO 15189 standard, you’ve likely come across something called “assurance of results validity.” You might have some questions about it at this point.
If that’s the case, don’t worry! Today, we bring you a guide where we’ll cover everything needed to create a plan for ensuring the validity of results in your clinical laboratory according to ISO 15189.
Here, you’ll learn how to construct two fundamental procedures: internal quality control (IQC) and external performance assessment (EQA).
Keep reading to discover how to ensure reliability in your clinical laboratory’s results.
Here we go!
What is a plan for ensuring the validity of results?
Within the context of the ISO 15189 standard, a plan for ensuring the validity of results is a tool that allows you to achieve a primary objective: identifying trends and deviations in terms of results.
A trend could be, for example, a persistent systematic error in the results that causes the values to always have a positive bias in the tests.
In addition to this main objective, a plan for ensuring the validity of results enables you to:
- Monitor the accuracy and truthfulness of your methods.
- Detect immediate errors.
- Conduct ongoing monitoring of the performance of your test methods.
- Identify needs for staff training or coaching.
- Allows for comparing the performance of test execution with other laboratories.
- Provides objective evidence to assess the quality of the tests.
In short, this plan is an indispensable tool that you must implement in your laboratory in order to guarantee the reliability of your results. This is the case whether you wish to become accredited under the ISO 15189 standard or not.
ISO 15189:2022 requirements related to ensuring the validity of results
Now that you understand the importance of implementing a plan like this, we will give you a summary of the requirements given in the standard so that you can understand them once and for all and avoid having to read and reread the standard.
Within clause 7.3.7.1 of the standard, it is established that a clinical laboratory must have a procedure to ensure the validity of results.
This procedure must be able to identify possible deviations and apply statistical techniques to review the results.
In order to comply with this requirement, your laboratory must create two fundamental procedures.
A procedure for internal quality control (IQC) and one for assessing external quality performance (EQA).
The requirements related to the creation of IQC are found in clause number 7.2.7.2. Within this, some items that IQC must comply with are established, among which are:
- The correct choice and evaluation of an IQC procedure.
- The correct selection and use of quality control material for IQC, such as certified reference materials. Additionally, it indicates what to do in case this control material is not available.
- The frequency, number, and type of quality controls performed.
- It indicates how the results should be recorded. For example, the use of control charts.
- Establishes that an IQC must have performance requirements or values and that such must be evaluated frequently.
- Additionally, guidelines are established to address situations where a deviation is identified that could affect clinical decisions.
On the other hand, clause 7.2.7.3 establishes the requirements related to the external performance assessment procedure (EQA). We can summarize these as follows:
- You must select an appropriate EQA program. The most common external assessment methods are proficiency testing or inter-laboratory trials.
- If there is no established External Quality Assessment (EQA) program, an alternative EQA mechanism for inter-laboratory comparison, such as the exchange of samples with other laboratories, should be considered.
- The laboratory management must monitor the EQA results and participate in the implementation of corrective actions.
Now that you know the requirements to be met, let’s give you a guide where we clarify how to create an IQC and an EQA.
How to create an Internal Quality Control (IQC) plan
When creating an internal quality control plan, you will come across different guidelines. One of the most important and considered standard provides a series of six steps.
See each of them below:
Step 1. Define the quality requirements of the test methods
When you want to create a suitable IQC plan, start by defining the quality requirements of your implemented methods.
These requirements are nothing more than the accuracy objectives you want to achieve. When defining these accuracy objectives, you should consider two aspects:
- Acceptable clinical performance: this is related to the accuracy of the results and how they contribute to the clinical method process.
- Capabilities of the current procedures: this takes into account the limitations of the techniques used in the laboratory.
One way you can define these objectives is by implementing the concepts of Total Allowable Error and Allowable Error Limit.
There are many approaches you can use when defining and calculating these two values. Below, observe two of these main approaches:
- Traditional approach: stay updated on everything related to your method, be attentive to your team’s recommendations.
- Regulatory approach: use limits established in regulations.
Step 2. Determine the method’s bias and precision
After defining the accuracy requirements in terms of total allowable error, it is necessary to determine two parameters: trueness and precision.
Trueness is a measure of bias, and precision is a measure of the variability of the data.
These values, in turn, can be calculated through the mean and standard deviation. For this, you can follow an approach where you obtain a series of initial data and then, from them, obtain the values of mean and standard deviation.
Then, these values will be used to determine the acceptable limit values within a control chart, also known as a control chart.
Step 3. Determine an IQC Procedure
An IQC procedure is a program in which we analyze control materials, such as reference material, over a determined period. The program should consider the following:
- Frequency of quality control.
- Number of quality controls.
Below, we detail these two aspects in two additional secondary steps:
Step 3.1. Quality Control Frequency
This refers to the time between each quality control performed. There are various guidelines for defining these control frequencies. Here, we present you with five:
- Strategy No. 1: schedule quality controls at fixed intervals.
- Strategy No. 2: schedule random quality controls within a fixed period.
- Strategy No. 3: schedule quality controls at random intervals.
- Strategy No. 4: schedule controls at fixed intervals and then controls at random intervals, or vice versa. That is, it’s a combination of the three previous strategies.
- Strategy No. 5: establish a fixed period of 8 hours between each quality control test, over a 24-hour period.
Step 3.2. Number of Quality Controls
Before performing the number of control measurements (N) used to assess the quality of an analysis, consider the following:
N represents the total number of measurements, which can be:
- Replicates of the same material: if a material is measured twice, N is 2.
- Individual measurements of various materials: if a different material is analyzed and one measurement is made on each, N is equal to the number of materials analyzed (for example, if 2 materials are analyzed, N is 2).
- Replicates of measurements on various materials: if several materials are analyzed and the measurement is repeated on each, N would be the product of the number of materials by the number of replicas made on each.
The number of quality controls in a clinical laboratory depends on the number of analyses or laboratory tests they perform per day. Depending on this value, the following is recommended:
- If your laboratory performs fewer than 50 tests per day, perform at least one replicate of a material, that is, N=2.
- Between 50 and 100 analyses per day, use two materials and perform a control test on each, with which you get an N value of 2.
- For more than 100 analyses per day, perform a duplicate for two materials, with which you get an N value of 4.
Step 4. Evaluate the Performance of the IQC
Before implementing an internal quality control (IQC) procedure, know and evaluate its performance.
One way you can do this is by using “Operating Process Specifications” (OPSpecs).
OPSpecs are derived from a model that allows evaluating three key aspects:
Precision: how close the measurements are to each other repeatedly.
Trueness: how close the measurements are to the true value.
Quality Control (QC): the processes to ensure precision and trueness over time.
OPSpecs can be presented in table form. They indicate the acceptable limits for inaccuracy, considering the level of quality assurance provided by a specific quality control procedure.
This is a tool you can implement when comparing different IQCs, allowing you to choose suitable quality control programs. Additionally, it optimizes the quality control process, avoiding excess or lack of controls.
In summary, OPSpecs are a valuable tool for ensuring the quality of analytical measurements through proper quality control planning.
Step 5. Set Performance Goals for the IQC
The main goal of an internal control program is to detect all possible deviations without unnecessarily repeating tests.
When defining the IQC performance objectives, you can take into account the probability of a false rejection of a deviation and the number of samples run until a deviation is detected.
Ideally, the false rejection probability would be 0%. However, this is not feasible in practice. The recommended maximum limit value for this probability is 5%.
Moreover, the greater the number of samples executed before detecting a deviation should be very high. For a 5% false rejection, this corresponds to a number of run samples of 20.
Step 6. Choose the IQC
Once the recommendations given in the previous section have been considered, you will have the opportunity to choose a suitable IQC.
To choose or evaluate a suitable IQC, always consider:
- Total acceptable error (TE_a).
- IQC performance.
A suitable CQI procedure has a minimum probability of 90% of detecting medically important errors and a maximum probability of 5%, ideally less than 1%, of generating false rejections.
Guide for Conducting an External Quality Assessment (EQA)
External quality assessment is an objective procedure that allows evaluating a laboratory’s performance, implemented by an external agency.
There are different methods to perform an EQA, among which inter-laboratory tests or proficiency tests stand out.
In these tests, an external provider supplies unknown samples to a group of laboratories. The samples are analyzed, compared, and sent to the laboratories.
Here you can take into account this series of steps when creating your procedure to implement an EQA:
Step 1: Define the Scope of the EQA
In this section, you must identify the analysis methods of your laboratory to be evaluated within an EQA.
Once you select the methods to evaluate, consider the frequency with which you will participate in these types of tests. If possible, it is recommended to participate once a year.
After considering these aspects, identify the EQA providers in your country.
Step 2: Select the EQA Provider
When you have the list of providers, first consider the provider’s accreditation. Ideally, proficiency test providers should be accredited. To verify this, check that the laboratory is accredited under ISO 17043.
When selecting these providers, ensure that the proficiency tests they offer allow evaluating all stages of the analytical process, such as the pre-analytical, analytical, and post-analytical phases.
Finally, and importantly, make a cost-benefit evaluation when comparing different providers, in case there are several for your tests to evaluate.
Step 3: Register for an EQA Program
Once you have selected the provider, be aware of the dates on which the external entity opens the calls for the tests.
Register considering the external entity’s form, provide the required information, and pay the registration cost.
Step 4: Receive and Analyze the EQA Samples
This may be one of the most crucial stages within the external evaluation process. For this, you should consider the following aspects:
- Follow the provider’s instructions regarding the handling and analysis of the samples. During the analysis of the samples, consider using the test methods routinely used in the laboratory.
- Properly record the test results.
- Perform the respective internal quality controls, use the appropriate quality control material, and record the related results.
Step 5: Report the Results to the Provider
Send the obtained results to the provider on the established dates. In this, follow the provider’s instructions and report any possible deviation that occurred in the process of reception, analysis, or interpretation of the result.
Step 6: Document the Procedure
Make sure to create a document in which you describe step by step how to participate in these types of proficiency tests.
In this procedure, indicate information on how to choose the provider, instructions for registration in the selected proficiency tests, how to receive and analyze the samples, and everything related to reporting the results and evaluating the laboratory’s performance.
External performance evaluation (EQA) is an indispensable tool in the clinical laboratory. Through it, you can ensure a higher level of quality in your organization.
Consider the aspects given in this section to complement the plan for ensuring the validity of the results.
In conclusion
Creating a program for ensuring the validity of results, based on ISO 15189, is a future investment for your laboratory.
By properly creating it and continuously reviewing it, you will be assured of obtaining reliable results.
In this guide, we have given you basic guidance to create the IQC and EQA procedures, which are two fundamental pillars to build a plan for ensuring the validity of the results.
Make sure to have this information handy; I hope the waters are calmer now that you have this tool to navigate the laborious task of creating this plan.
