In molecular diagnostics, precise and reliable testing is critical for patient diagnosis, prognosis, and monitoring. Laboratories specializing in molecular testing must adhere to the quality control requirements of ISO 15189:2022 to ensure the ongoing validity of their examination results. Here’s how these requirements can be applied specifically within a molecular test discipline:
a) Establishment of IQC Procedures:
- Clinical Application Consideration: Molecular laboratories need to tailor their IQC procedures based on the clinical application of the test. For instance, the detection sensitivity required for a PCR test to diagnose an acute viral infection may be different from that needed for monitoring viral load in a chronic infection setting.
- Detection of Lot-to-Lot Variations: The IQC procedure must allow for the detection of variations in reagents or calibrators. This means not changing the lot of control materials on the same day as a new reagent lot is introduced, such as when a new batch of PCR primers is used.
- Use of Third-Party IQC Material: Consideration should be given to third-party control materials for molecular assays, such as those used in quantitative nucleic acid testing, to provide an independent assessment of the test’s accuracy.
b) Selection of Fit-for-Purpose IQC Materials:
- Stability: Molecular labs must select control materials that are stable, ensuring that the materials maintain their integrity over time. This is particularly important for controls used in genetic mutation analysis, where the integrity of nucleic acids is paramount.
- Matrix Similarity: Control materials should closely resemble the patient sample matrix. In molecular testing, this might involve using control materials that contain human genomic DNA for tests like SNP genotyping.
- Reactivity to Examination Method: The reactivity of IQC materials should closely mimic that of patient samples. For example, in an RT-PCR assay for infectious diseases, control RNA should amplify with the same efficiency as patient-derived RNA.
- Clinically Relevant Challenge: IQC materials should provide a challenge to the examination method at clinically relevant levels. For instance, in a viral load assay, control materials should have viral RNA concentrations close to the clinical cut-off values, ensuring the assay’s sensitivity and specificity are adequate for patient care decisions.
c) Alternative Methods for Internal Quality Control: In the absence of suitable IQC materials, molecular biology labs must consider other methods for ensuring quality control.
- Trend Analysis of Patient Results: Labs can analyze trends in patient test results, such as using statistical methods like moving averages. For instance, in a molecular test for a specific genetic marker, observing an unusual increase or decrease in the frequency of positive results could indicate a potential issue with test sensitivity or specificity.
- Comparison with Alternative Procedures: Regularly comparing results with those obtained from an alternative validated procedure helps ensure accuracy. For example, results from an in-house developed PCR assay might be compared with a commercially available kit that is traceable to higher order references.
- Retesting Retained Samples: Retesting previously analyzed patient samples can help verify the accuracy of recent test results. This is especially relevant in molecular diagnostics, where the reproducibility of findings is critical for clinical decision-making.
d) Frequency of IQC: The frequency of conducting IQC should be based on the examination method’s stability and the potential risk to the patient from incorrect results. High-stakes tests, such as those used for cancer genotyping, may require more frequent quality control than more robust assays.
e) Data Recording and Analysis: Molecular biology labs must meticulously record IQC data to facilitate the detection of trends and shifts. Statistical techniques, such as control charts, can be used to monitor the performance of assays over time.
f) Review of IQC Data: Regular review of IQC data against specified acceptability criteria is essential. Any deviation from these criteria should prompt a thorough investigation to determine the cause and implement corrective measures.
g) Management of IQC Failures:
- When IQC fails to meet the established criteria, indicating the possibility of clinically significant errors, the affected results must be rejected. For example, if a control sample in a gene expression assay fails, all patient results since the last successful control would need to be reviewed and potentially retested.
- The results from patient samples tested after the last successful IQC but before an identified failure should also be re-evaluated to ensure their validity.
By strictly adhering to ISO 15189:2022 standards for internal quality control, molecular testing laboratories can confidently provide clinicians and patients with accurate and clinically relevant results, supporting effective patient management.
About the Author
Dr. Sambhu Chakraborty is a distinguished consultant in quality accreditation for laboratories and hospitals. With a leadership portfolio that includes directorial roles in two laboratory organizations and a consulting firm, as well as chairman of IOL ( An ILAC stakeholder organisation), Dr. Chakraborty is a respected voice in the field. For further engagement or inquiries, Dr. Chakraborty can be contacted through email at director@iaqmconsultants.com and info@sambhuchakraborty.com. Additional resources and contact information are available on his websites,https://www.quality-pathshala.com and https://www.sambhuchakraborty.com or via WhatsApp at +919830051583