Insufficient Internal Quality Control

Insufficient internal quality control is one of the leading causes of lost analytical reliability in laboratories. When there is no structured system to continuously monitor method performance, deviations go unnoticed and systematic errors can become established without immediate detection. A common example: an instrument with a gradual bias can keep releasing results “within range” for weeks if the laboratory does not use control charts or reference materials to detect the trend.

In an analytical laboratory, it is not enough to execute the method correctly at a single point in time. It is necessary to ensure that it remains under control over time. Internal quality control serves exactly this function: verifying that the process continues to produce consistent results within acceptable limits.

What ISO/IEC 17025 Requires for Internal Quality Control

The ISO/IEC 17025 standard requires laboratories to monitor the validity of results through internal quality controls, including participation in proficiency testing and the use of reference materials, with records that allow trends to be identified before they become nonconformities. Accredited laboratories are accountable to INMETRO/Cgcre — Brazil’s national accreditation body — for this continuous monitoring.

What Is Internal Quality Control in the Laboratory?

Internal quality control consists of the set of activities used to monitor the performance of analytical methods during routine operation. This includes the use of control samples, independent standards, replicates, and trend analysis over time.

These controls make it possible to assess whether the analytical system is stable, precise, and accurate. They also help identify variations before they affect reported results.

Unlike validation, which demonstrates the method’s suitability at a specific point in time, internal quality control ensures that this suitability is maintained continuously.

Consequences of Insufficient Internal Quality Control

When quality control is insufficient, the laboratory loses visibility into the method’s actual performance. As a result, systematic errors can accumulate without being detected.

Results may appear consistent while actually being offset from the true value. This is especially critical in quantitative analyses, where small deviations can affect important decisions.

Furthermore, the absence of continuous monitoring makes it harder to identify trends such as reagent degradation, equipment wear, or changes in method performance.

From a regulatory standpoint, the lack of internal quality control is interpreted as a weakness in the management system. Audits frequently require evidence of continuous monitoring and critical review of the data generated.

Essential Elements of Effective Quality Control

Effective internal quality control must include independent control materials with known values that remain stable over time. These materials should be analyzed regularly, alongside routine samples.

It is also essential to establish acceptance limits based on historical data and statistical criteria. These limits make it possible to identify deviations objectively.

Trend analysis is also essential. Simply checking point-in-time conformity is not enough. It is necessary to evaluate behavior over time to detect gradual changes in the system.

Another important point is defining clear actions in case of deviation. When a control indicates a failure, there must be a structured procedure for investigation, impact assessment, and correction.

Integrating Quality Control into the Analytical Routine

Quality control should not be treated as a step separate from the analysis. It needs to be integrated into the routine, carried out systematically and consistently.

This includes proper planning of control frequency, periodic review of results, and clear communication between the technical team and management.

Furthermore, the data generated must be used for decision-making. A control system that only records information, without critical analysis, does not fulfill its purpose.

LIMS as Support for Internal Quality Control

In this context, a LIMS, Laboratory Information Management System, can significantly strengthen internal quality control. The system makes it possible to automatically record control results, generate trend charts, and identify deviations in real time.

In addition, a LIMS can configure acceptance limits and issue alerts when results exceed those limits. As a result, the response to deviations becomes faster and more structured.

Another significant advantage is data centralization. The complete history of method performance becomes available for analysis, facilitating audits and technical investigations.

The system also allows control results to be linked to equipment, reagents, and operators, expanding the ability to identify potential causes of variation.

However, it is important to note that a LIMS does not replace critical analysis. It organizes and automates monitoring, but data interpretation and decision-making remain the responsibility of the technical team.

Conclusion

Insufficient internal quality control compromises the laboratory’s ability to detect deviations and ensure the consistency of results over time. Without continuous monitoring, the analytical system operates without a clear performance reference.

Implementing robust quality control means establishing objective criteria, analyzing trends, and acting quickly on deviations. It also strengthens data reliability and regulatory compliance.

When this control is integrated with tools such as a LIMS, the laboratory gains agility, traceability, and greater analytical capacity. In this way, quality control stops being a one-time check and becomes a continuous improvement process.

Without this continuity, the laboratory only notices analytical drift after it has already compromised results delivered to the client — when the correction comes too late.