The fundamental objective of any clinical laboratory is to have an accurate and precise impact on clinical diagnosis. Today we know that 70% of medical decisions are based on the results issued by the laboratory, being the fundamental pillar in clinical risk management.

One of the biggest challenges facing clinical laboratories today is to implement a quality control plan that is grounded in the reality of the processes, adding value to the diagnosis. Beyond a legal requirement, quality control is the cornerstone: we cannot speak of diagnostic accuracy when the laboratory does not have correctly and effectively implemented internal and external quality control programs.

At In Vitro News, we talked about external quality control with Magda Romero Ríos, bacteriologist, master’s degree in senior business management and specialist in integrated health services management. She currently works as manager of the quality line at ANNAR Health Technologies.

Initial question: Why are you passionate about external quality control?

Quality control strategies include an internal quality control plan, which is performed on a recurring basis to ensure measurement accuracy, and participation in interlaboratory comparison programs or external quality control programs.

These programs are important because they allow the laboratory to monitor the veracity of the measurement methods. In addition, since they are blind samples, they allow the evaluation of the whole process of laboratory care, from the pre-analytical, analytical and post-analytical phases, including the competence of the technical personnel.

What is the main purpose of applying quality controls in the laboratory?

To guarantee medically useful results, i.e. results that reflect the reality of the patient’s clinical condition and therefore allow an accurate diagnosis to be made.

What types of activities are involved in having an external quality control program?

The first activity is to select the appropriate external quality control. There are multiple alternatives in the national and international market. I have always thought that all quality control programs are useful regardless of the brand, some have certain advantages and others do not, but in general they are comparable. The greatest efficiency then considered to be looking for a reliable supplier that not only sells or provides the product per se, but also offers the laboratory comprehensive solutions that maximize the use of these products through consulting strategies in analytical quality and analytical software tools.

The second activity would be aimed at training personnel in the use of the acquired program, accompanied by training in the use of the registration platform and the interpretation of quality reports.

Likewise, the laboratory must have a quality plan in which it determines and identifies the applicable quality control programs, the description of use and something fundamental: the strategies for solving faults and defects based on standardized instructions.

Finally, the last activities would be related to the processing of the evaluation schemes and the analysis and decision making based on the results obtained.

How can the performance of external quality control be evaluated?

The performance of the external quality control can be evaluated through the statistical indicators that are displayed in the results report that each participant receives.

For example: some programs use for performance evaluation the Z-Score indicator, this indicator is an expression of the veracity of the analysis method expressed in standard deviations, the mathematical formula to define it is quite simple: the value obtained by the laboratory minus the mean of the results obtained by the participants divided by the standard deviation of the participants. This indicator is expressed in standard deviations and indicates how far away or close the laboratory’s result is compared to the target value. Ideally, a test with excellent analytical performance should have a Z-score of zero, however, we know that all analytical methods present a percentage of systematic error or bias, so it is considered a true method if this indicator remains in a range of +2 or -2 standard deviations. Values that exceed these limits should be rigorously analyzed in order to determine the cause and define an action plan.

What are the main challenges laboratories face when implementing external quality control?

It is common to find laboratories that invest significant resources in the purchase of external quality control programs, however, they do not have defined quality protocols or they are deficient, therefore, results are not analyzed, actions are not implemented or if these activities are carried out, they do not lead to a correct follow-up.

The second challenge is to ensure that the statistical measures applied are the correct ones, i.e. that the evaluation of the veracity of the results is performed by comparison with quality objectives that are associated with clinical risk or impact, creating these specific protocols for each test and according to the target patient population is clearly a challenge.

The third challenge is the constant uncertainty of our healthcare system, where every day coordinators must reduce costs, sometimes sacrificing analytical quality.

Should laboratories consider implementing an external quality control program?

Of course, not only because it is mandatory, it is a requirement given by our unique Health Qualification System, but also because, as we have commented in previous questions, it is the strategy through which we can guarantee accurate results and safety for our patients.

What characteristics should users consider when selecting an external quality control program that benefits patient safety?

According to ISO 17043:2023, which defines the technical and management requirements for the accreditation of proficiency testing programs, these are the characteristics to take into account when selecting an external quality control program:

The homogeneity and stability of the matrices that make up the samples of the external quality control program, which must be manufactured based on human matrices and guarantee the necessary stability and homogeneity taking into account distribution and logistic times.

Switchability is the attribute that ensures that the samples used in external quality control programs can be used in all analytical systems on the market. It is important for the laboratory to ensure that the control matrix is validated in the analytical platform in use.

Number of samples evaluated in the program cycle. This attribute is related to the sensitivity of the program to detect analytical errors; the greater the number of samples evaluated in the cycle, the greater the sensitivity to detect some type of error in the analytical system. The sensitivity is not related to the frequency of shipments, the laboratory can choose the frequency that best suits its logistical and operational needs.

Traceability of the measurement, it is important for the laboratory to find out against which group it will be compared: peer group with equal or identical analytical conditions, method group or all participating laboratories. In the clinical laboratory there are analytical tests that are not harmonized, i.e., between one methodology and another there are differences in the results without implying an error in the method. This is probably due to the fact that they use calibration standards with different traceability. For this reason it is always preferable that the comparison be made against the peer group.

Number and consistency of participants. There are different sources that provide some guidelines on the minimum number of participants that an external quality control program should have in order to be considered statistically robust. For example, according to ISO13528 a minimum number of 10 participants is considered, according to the guidelines of the International Union of Pure and Applied Chemistry a minimum of 30 participants is considered feasible and in experience we observe that the main providers of external controls worldwide use a minimum of 5 to 10 participants.

Finally, the usefulness of the report, i.e. to evaluate the statistical data provided, the incorporation of graphs and universally applicable quality indicators such as the z-score or the IDS.

Now, in my professional experience, I would add one last attribute and that is the continuous support and training that the supplier provides to the laboratory in order to maximize the analysis of the quality reports.

Recommendation that we should take into account:

The impact of the responses should be oriented towards the safety of the users’ internal processes, with a focus on patient safety, not from the commercial role.