Validation of Hematological test results Aligning with ISO 15189:2022 Quality Control Standards.

In hematology, the quality and accuracy of laboratory testing are vital for patient diagnosis and treatment. ISO 15189:2022 provides a framework for Internal Quality Control (IQC) that hematology laboratories can follow to ensure their examination results are valid and reliable.

Developing IQC Procedures for Hematology: a) Hematology laboratories must have robust IQC procedures that align with the intended clinical use of the examinations. For instance, the performance specifications for a complete blood count (CBC) differ when used to monitor a chronic condition like anemia versus its use in an acute setting, such as in the case of suspected infection.

1. Clinical Application Consideration: If a CBC is used to monitor a patient with chronic anemia, the laboratory must ensure that the red blood cell indices are accurate and precise, as even slight deviations could impact clinical decisions regarding treatment adjustments.
2. Lot-to-Lot Reagent and Calibrator Variation: It’s crucial to detect variations in reagents and calibrators. A lab must avoid changing control materials when introducing a new lot of reagents for hemoglobin measurement to ensure that any observed variation is due to the new reagent lot and not conflated with a change in the control material.
3. Use of Third-Party IQC Material: Using third-party control materials for platelet count assays can provide an independent check against the instrument and reagent manufacturer’s control materials, ensuring that the lab’s quality control processes are impartial and effective.

b) Selecting appropriate IQC material is critical for accurate hematology testing:

1. Stability: Stability is crucial, especially for parameters like coagulation factors, which may degrade quickly if not stored properly. The IQC material must be stable enough to ensure consistent quality control over its shelf life.
2. Matrix Similarity: IQC materials should closely match the matrix of patient samples. For white blood cell differential counts, the control material should have a similar cellular composition to what would be expected in patient samples.
3. Reaction to Examination Method: Control materials should react to testing methods in the same way as patient samples. For example, control samples for erythrocyte sedimentation rate (ESR) should display sedimentation behavior that closely mimics actual patient samples.
4. Clinical Challenge: The IQC material should challenge the hematologyanalyzer at clinically relevant levels, especially near decision thresholds such as the lower limit of the normal range for leukocytes, where clinical decisions regarding infection management may be made.

Alternative Methods for Internal Quality Control (IQC): c) In the event that suitable IQC material is unavailable, hematology laboratories must employ alternative methods for internal quality control.

1. Trend Analysis: Laboratories can perform trend analysis of patient results, such as utilizing a moving average or tracking the percentage of patient samples with results above or below established clinical thresholds. For instance, a significant shift in the average hemoglobin values over time might indicate an issue with the hematologyanalyzer or reagents used.
2. Comparison with Alternative Procedures: Regularly scheduled comparisons of patient results to those from an alternative, validated procedure can provide additional assurance of test validity. A hematology lab could compare its internal CBC results with those obtained from a reference laboratory that uses a different analyzer calibrated to the same or higher metrological standards.
3. Retesting Retained Samples: When a discrepancy in results is suspected, retesting retained patient samples can help determine the reliability of recent results. For example, if a control result for a prothrombin time test is outside the acceptable range, previously tested patient samples might be retested to ensure their results are still valid.

Frequency and Review of IQC: d) The frequency of IQC is determined by the stability and robustness of the examination method and the potential risk of harm that could arise from incorrect results. In hematology, high-frequency testing might be necessary for assays like platelet function tests, which are critical for patients on anticoagulant therapy.

Data Recording and Analysis: e) IQC data must be meticulously recorded to facilitate the detection of trends and shifts. Statistical analysis, such as Westgard rules applied to daily quality control results for white blood cell counts, can be critical for early detection of systematic errors.

IQC Data Review: f) Review of IQC data against specified acceptability criteria is conducted at regular intervals. This review process ensures that the laboratory’s performance is consistently within the established limits and that patient results are reliable.

Handling IQC Failures: g) Should IQC fail to meet the acceptability criteria, laboratories must prevent the release of patient results.

1. Results that do not meet the defined acceptability criteria and are likely to contain clinically significant errors must be rejected. Affected patient samples should be re-examined once the error has been rectified. For example, if an error is identified in a leukocyte differential count, all affected patient samples would need to be retested after corrective actions are implemented.
2. The results for patient samples tested after the last successful IQC event must be re-evaluated to ensure their accuracy. This might involve retesting samples processed since the last confirmed accurate IQC result for critical tests such as hemoglobinopathies.

By integrating these robust IQC measures, hematology laboratories can ensure the consistency and accuracy of their test results, thus providing clinicians with the reliable information they need for patient management and care.Top of Form

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By adhering to these IQC standards, hematology laboratories can guarantee the validity of their testing methods, ultimately improving patient care. Regular peer reviews of examination results further enhance the reliability of interpretations and ensure that patient diagnoses are based on sound laboratory evidence.

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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 chairmanship in a prominent laboratory organization, 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