How to do External Quality Assurance (EQAS) or Proficiency test (PT) trend analysis in a medical laboratory ?

External Quality Assurance (EQAS), also known as Proficiency Testing (PT), is a crucial aspect of ensuring the accuracy and reliability of testing performed in a medical laboratory. Trend analysis in EQAS/PT involves analyzing the laboratory’s performance over multiple rounds of testing to identify patterns, improvements, or potential issues. Here’s how to perform EQAS/PT trend analysis in a medical laboratory, along with examples:

Steps for EQAS/PT Trend Analysis:

1. Data Collection:
2. Collect the EQAS/PT results for each testing round over a specified period
3. Ensure you have data for the same analyte or parameter tested in each round.
4. Data Preparation:
5. Organize the data in a structured format, including the laboratory’s results and the expected target values provided by the EQAS/PT program.
6. Calculation of Performance Metrics:
7. Calculate performance metrics for each round, such as mean, standard deviation, coefficient of variation (CV), or Z-score (a measure of how far a result is from the mean in terms of standard deviations).
8. Control Chart Creation:
9. Plot the calculated performance metrics on a control chart over the testing rounds.
10. The X-axis represents the testing rounds, and the Y-axis represents the performance metric values.
11. Identification of Trends:
12. Analyze the control chart to identify trends, patterns, or changes in the laboratory’s performance over time.
13. Look for significant shifts in mean values, increasing or decreasing variability, or patterns of improvement or decline.
14. Root Cause Analysis:
15. If you identify negative trends, investigate potential root causes. This could involve reviewing procedures, reagent lots, instrument maintenance, personnel changes, etc.
16. Process Improvement:

Based on the analysis, implement process improvements if necessary. This could involve refining procedures, providing additional training, or addressing any identified issues.

• Documentation:
• Maintain detailed records of the EQAS/PT results, control charts, investigations, and actions taken for future reference and audits

Example: Hemoglobin Measurement in a Laboratory

Let’s consider a clinical laboratory that performs hemoglobin measurements using a specific method. The laboratory participates in an EQAS/PT program for hemoglobin testing. Here’s how trend analysis might be conducted:

1. Data Collection:
2. Collect EQAS/PT results for hemoglobin testing over the past 10 rounds
3. Data Preparation:
4. Organize the data in a table format, including the laboratory’s results and the target values provided by the EQAS/PT program
5. Calculation of Performance Metrics:
6. Calculate the mean and CV for each round’s haemoglobin results.
7. Control Chart Creation:
8. Plot the mean and CV values on separate control charts over the 10 rounds.
9. Identification of Trends:

Analyze the control charts:

• Are there any shifts in mean values away from the target?
• Is there an increase in variability (CV) over time?
• Are there patterns of consistent improvement or decline?
• Root Cause Analysis:
• If you notice a shift or consistent decline in performance, investigate potential causes such as reagent changes, instrument maintenance, or operator error.
• Process Improvement:
• Based on the analysis, if you identify any issues, take corrective actions. This might involve retraining staff, verifying reagent lots, or calibrating instruments
• Documentation:
• Document the EQAS/PT results, control charts, investigation findings, and actions taken for future reference

By analyzing EQAS/PT data and conducting trend analysis, the laboratory can proactively identify performance trends, make improvements, and ensure ongoing accuracy and quality in their testing processes

In this example, we’ll focus on mean and CV as the performance metrics.

Hemoglobin EQAS/PT Data:

Calculation of Performance Metrics:

Mean = Sum of Laboratory Results / Number of Rounds
Mean = (12.3 + 12.8 + … + 12.9) / 10 = 12.54 g/dL

CV = (Standard Deviation / Mean) * 100
Standard Deviation = √[((12.3 – 12.54)^2 + (12.8 – 12.54)^2 + … + (12.9 – 12.54)^2) / 9]
CV = (Standard Deviation / 12.54) * 100

Control Chart Creation:

Now, let’s plot the mean and CV values on separate control charts:

Mean Control Chart:

CV Control chart

Trend Analysis:

From the control charts:

• The mean values are generally within the control limits, indicating consistency in the laboratory’s hemoglobin measurements.
• The CV values show relatively low variability, suggesting good precision in the measurements

Interpretation:

Based on the trend analysis:

• The laboratory’s mean hemoglobin measurements are consistently close to the target value
• he CV values demonstrate stable precision over the testing rounds

Recommendations:

Given the stability in mean and CV values, no immediate corrective actions are required. However, the laboratory should continue to monitor future EQAS/PT results to ensure ongoing accuracy and precision.

Remember that this example provides a simplified representation of EQAS/PT trend analysis. In a real-world scenario, you would consider more rounds of data and additional performance metrics, and you would thoroughly investigate any trends that fall outside control limits or indicate a decline in performance.

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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 resourcesand contact information are available on his websites, https://www.quality-pathshala.com and https://www.sambhuchakraborty.com, or via WhatsApp at +919830051583