In the intricate world of medical testing laboratories, the quality and accuracy of examination
methods are paramount. External Quality Assessment (EQA) programs are widely recognized
for their role in maintaining high standards, but what happens when such a program is
unavailable or unsuitable? Laboratories must pivot towards alternative approaches to
safeguard their testing processes.
One innovative alternative is the in-depth analysis of different lot numbers of a
manufacturer’s end-user calibrator or trueness control materials. These alternatives are not
merely stop-gaps but are part of a systematic approach to quality assurance in laboratory
medicine.
Understanding the Alternative to EQA
In lieu of traditional EQA programs, laboratories can utilize materials provided by manufacturers, designed specifically to verify and validate the accuracy of test results. Here’s
how they can serve as a robust alternative:
- Calibrator Lot Analysis:
Laboratories can compare results from their assays using different lot numbers
of the same calibrator. Consistency across lots supports the accuracy of the
assay. A discrepancy, however, may indicate a need for recalibration or further
investigation into assay conditions. - Trueness Control Materials:
These are materials with established values that are used to confirm the true
response of an assay. By analyzing these control materials, laboratories can
assess if their examination methods are producing results that are true to
known standards.
The Process
Implementing this alternate approach entails a structured process:
- Lot Selection and Sourcing:
Obtain multiple lot numbers of calibrators and control materials from the
manufacturer, ensuring they are designed for the specific tests being assessed. - Methodical Analysis:
Systematically test these lots as part of the regular examination schedule. This
includes assessing them under the same operational conditions as patient
samples. - Data Comparison and Interpretation:
Compare results across different lots and against known values. Look for
consistency in performance, noting any trends or variations. - Corrective Actions:
If inconsistencies arise, determine the root cause and take corrective action.
This might involve recalibration, staff retraining, or modifications to the
examination method.
Advantages of an Alternate Approach
Customization: Laboratories can tailor the use of these materials to their specific
needs, focusing on the areas most critical to their practice.
Flexibility: This method allows laboratories to conduct assessments on their own
schedule, without relying on external EQA program timelines.
Control: There is a greater level of control over the variables involved in the testing
process, which can lead to more nuanced insights into the performance of
examination methods.
Challenges and Considerations:
Regulatory Compliance: Laboratories must ensure that their alternate approach
meets all regulatory and accreditation requirements.
Documentation: Meticulous documentation is necessary to demonstrate the validity
of this alternative method of quality assessment.
Expertise: It requires a high level of expertise to interpret the results of calibrator and
control material analyses correctly.
Conclusion
While traditional EQA programs play a central role in external validation, alternative
approaches like the analysis of calibrator lots and trueness control materials offer a viable
path to achieving and maintaining accuracy and reliability in laboratory testing. As healthcare
continues to evolve, laboratories must be adept at employing both standard and innovative
methods to ensure the highest quality in patient care diagnostics. This alternative approach
stands as a testament to the resilience and adaptability of modern medical laboratories in their
ongoing quest for excellence.
Hypothetical Scenario: Using Different Lot Numbers of Manufacturer’s Calibrators
Background:
A laboratory conducts routine cholesterol testing using a specific enzymatic assay. The usual
EQA program is not available for the next testing cycle.
Alternative Methodology:
The laboratory decides to use different lot numbers of the manufacturer’s calibrators to
monitor their cholesterol test performance.
Process:
- Acquisition: Obtain two different lot numbers of calibrators from the assay
manufacturer. - Testing: Perform the cholesterol test using the current lot number of the calibrator as
per the daily routine. Simultaneously, run the same tests using the new lot number of
the calibrator. - Data Recording: Record the results from both sets of calibrators meticulously.
- Comparison and Analysis:
Compare the results obtained from both lot numbers.
Assess any differences in the performance characteristics (e.g., sensitivity,
specificity, linearity, precision) of the assay when using the different
calibrators.
Evaluate if the results are within the acceptable range of variation as defined
by the manufacturer or the laboratory’s own validation data. - Statistical Analysis:
Use statistical methods to analyze the data for significant differences.
Determine if the new lot number of calibrators provides consistent results
compared to the established lot.
- Documentation and Justification:
Document the entire process and outcome.
Justify the use of different lot numbers as a suitable alternative to EQA,
providing evidence that the performance of the examination method remains
unaffected or within an acceptable range of variation. - Review and Validation:
Have the data reviewed by a peer or an external consultant to validate the
methodology and findings.
Adjust the testing protocol if there is significant variation, and validate the
new calibrator lot before routine use.
Conclusion:
The laboratory demonstrates through this correlation study that it can effectively monitor its
examination method performance without an EQA program by using alternative calibrator
lots, thereby ensuring ongoing test accuracy and reliability.
This alternative approach demands rigorous documentation and methodological transparency
to be accepted as a valid performance monitoring technique. It is also crucial to keep in mind
that any significant differences observed would need to be investigated and understood to
ensure continued test validity.
CASES AND EXAMPLES
Here is
hypothetical examples that illustrate how a medical laboratory might use different lots of
manufacturer’s calibrators or control materials to monitor test performance in lieu of an
External Quality Assessment (EQA) program:
Example 1: Hematology – WBC Count Calibration
Background:
Test: White Blood Cell (WBC) Count
Issue: The usual EQA program for WBC count is temporarily unavailable.
Alternative: Using different lot numbers of the manufacturer’s end-user calibrator to
monitor the performance of the hematology analyzer.
Technical Process:
- Calibrator Lots:
Current Lot: A123 (Control Mean: 7.5 x 10^9/L)
New Lot: A124 (Control Mean: 7.5 x 10^9/L) - Calibration Procedure:
Run daily WBC counts using both Lot A123 and Lot A124 over a period of
one week.
Each lot is tested in triplicate each day. - Data Collected:
Lot A123: Mean WBC count range over the week: 7.4 – 7.6 x 10^9/L
Lot A124: Mean WBC count range over the week: 7.3 – 7.7 x 10^9/L - Statistical Analysis:
Coefficient of Variation (CV) for A123: 1.33%
Coefficient of Variation (CV) for A124: 1.78%
Acceptable CV per lab standard: ≤ 2%
- Conclusion:
Both lots show CVs within the acceptable range.
The performance of Lot A124 is consistent with Lot A123.
The new lot is suitable for use as an alternative to EQA monitoring.
Example 2: Clinical Chemistry – Glucose Assay
Background:
Test: Blood Glucose Level
Issue: The EQA program does not cover the specific assay method used by the
laboratory.
Alternative: Using the manufacturer’s trueness control material from different lot
numbers to monitor the performance of the glucose assay.
Technical Process:
- Control Material Lots:
Current Lot: B101 (Assigned Value: 5.6 mmol/L)
New Lot: B102 (Assigned Value: 5.6 mmol/L) - Testing Protocol:
Perform glucose testing using control materials from both lots, alongside
patient samples, in each run for one month.
Each lot is assessed twice in each run. - Data Collected:
Lot B101: Mean glucose level range over the month: 5.5 – 5.7 mmol/L
Lot B102: Mean glucose level range over the month: 5.4 – 5.8 mmol/L - Statistical Analysis:
Standard Deviation (SD) for B101: 0.05 mmol/L
Standard Deviation (SD) for B102: 0.10 mmol/L
Total Error allowable for glucose: ± 0.15 mmol/L - Conclusion:
Both lots of control material are within the total allowable error for the
glucose assay.
Lot B102 shows a slightly higher variation but remains within the acceptable
limits.
The new lot can be effectively used for continuous performance monitoring.
In these examples, the laboratory has effectively used different lots of calibrators or control
materials to ensure their examination methods remain accurate and reliable. It is critical in
such scenarios to thoroughly document all procedures, results, and analyses and to have a
robust justification for the alternative methods chosen to maintain the integrity of laboratory
results.
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 resourcesand contact information are available on his websites, https://www.quality-pathshala.com and https://www.sambhuchakraborty.com, or via WhatsApp at +919830051583