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### Directions for using Normalized Method Decision Chart to Judge Performance

1. Define the analytical quality requirement for the test in the form of an allowable total error, such as given by the CLIA PT criteria for acceptable performance in a proficiency testing event. For example, TEa is 10.0% for cholesterol.
2. Evaluate the imprecision and inaccuracy of your method. From the replication experiment, calculate the SD or CV for the method. From the comparison of methods experiment, calculate the bias from t-test statistics if the mean of the comparative method is close to the medical decision level of interest, or use regession statistics to calculate the systematic error at the medical decision levels of interest.
3. Calculate your normalized operating point, which is your observed imprecision and inaccuracy expressed as a percentage of the allowable total error. For example, a 2% observed CV would be 20% of a 10.0% TEa; a 1% observed bias would be 10% of a 10.0% TEa. Use the Normalized OPSpecs Calculator available below.
4. Print the Normalized Method Decision Chart.
5. Manually plot your normalized operating point using the coordinates obtained from the calculator.
6. Judge performance on the basis of the location of your operating point.
• A method with “poor performance” does not meet your requirement for quality and is not acceptable for routine operation.
• A method with “marginal performance” will require a Total QC strategy that emphasizes well trained operators, limited rotation of operators, more expensive statistical QC (higher N, multirule type procedures), agressive preventive maintenance, careful monitoring of patient test results, and efforts to improve method performance.
• A method with “good performance” can be well-managed in routine service if you plan the statistical QC procedure carefully and are willing to spend the resources necessary to implement a multirule procedure with 4-6 control measurements per run.
• A method with “excellent performance” is easy to manage in routine service even with widespread rotation of many operators and can be controlled with minimum expense, usually with a single-rule QC procedure and a minimum of 2 control measurements per run.

### Directions for Using Normalized OPSpecs Charts to Select a QC Procedure

1. Define the analytical quality requirement for the test in the form of an allowable total error, such as given by the CLIA PT criteria for acceptable performance in a proficiency testing event. For example, TEa is 10.0% for cholesterol.
2. Evaluate the imprecision and inaccuracy of your method. To define your operating point, express your observed imprecision and inaccuracy as a percent of the allowable total error. For example, a 2% observed CV would be 20% of a 10.0% TEa; a 1% observed bias would be 10% of a 10.0% TEa. You can use the Normalized OPSpecs Calculator available on this website.
3. Obtain Normalized OPSpecs charts, such as those available here, for common control rules with N's of 2 and 4.
4. Plot your normalized operating point on the Normalized OPSpecs Chart for 90% AQA for control rules with N=2. For example, the cholesterol normalized operating point would be 20% on the x-axis and 10% on the y-axis.
5. a. Inspect the 90% AQA chart and select a control rule(s) whose operating limits are above your normalized operating point. Identify the control rule(s) from the key at the right side of the chart.
6. b. If no QC procedure can be selected in step 5a, try the 90% AQA & N=4 chart.
7. c. If no QC procedure can be selected in step 5b, and if your analytical method is very stable (and only occasionally has a problem), plot your normalized operating point on the Normalized OPSpecs Charts for 50% AQA & N=2, and if that doesn't work, plot your normalized operating point on the 50% AQA & N=4 chart..
8. If no QC procedure can be selected in steps 5a-c, use a "maximum" QC procedure such as the multirule procedure with N=4 or use the 2 SD limits with N=2.
9. Select at Total QC strategy on the basis of the error detection expected, as described in the Lesson on Total QC Strategies on this website.
10. Reassess for changes in method performance.
11. To Recap:
First: Normalized OPSpecs Chart for 90% AQA, N=2
Second: Normalized OPSpecs Chart for 90% AQA, N=4
Third: Normalized OPSpecs Chart for 50% AQA, N=2
Fourth: Normalized OPSpecs Chart for 50% AQA, N=4

### The Normalized OPSpecs Calculator (Javascript)

##### IMPORTANT: Your browser must support Javascript (Navigator 3.0 or higher). When entering data into this calculator, do not include units, % symbols, etc. Just enter the numbers by themselves. If you get an error message, reload the page and start over.
Step A. Enter the critical medical decision level (Xc):
NOTE: You must enter a decision level for this calculator to work!
Step B. Enter your Analytical Quality Requirement in concentration units (TEa) and calculate %:
Then
The answer will appear on the right. If you know the %TEa, you can enter it here directly. % TEa
Step C. Enter your observed method SD in concentration units:
Then
The answer will appear on the right. If you know the %CV, you can enter it here directly. % CV
Step D. Enter your observed method bias in concentration units:
Then
The answer will appear on the right. If you know the %Bias, you can enter it here directly. % Bias
Step E. Plot the following normalized operating point on one of the charts listed below:

A. To judge method performance from a validation experiment, use the Normalized Method Decision Chart.

B. To select a QC procedure, use on of the Normalized OPSpecs Charts.
For two control materials:

1. Try this chart first: Normalized OPSpecs Chart for 90% AQA, N=2
2. Try this Second: Normalized OPSpecs Chart for 90% AQA, N=4
3. Try this Third: Normalized OPSpecs Chart for 50% AQA, N=2
4. Try this Fourth: Normalized OPSpecs Chart for 50% AQA, N=4

For three control materials:

1. Try this chart first: Normalized OPSpecs Chart for 90% AQA, N=3
2. Try this chart second: Normalized OPSpecs Chart for 90% AQA, N=6
3. Try this chart third: Normalized OPSpecs Chart for 50% AQA, N=3
4. Try this chart fourth: Normalized OPSpecs Chart for 50% AQA, N=6