Establishing New/Changing Tests

Question 1

How many (minimum) healthy reference subjects per partition are required to;
1. Establish a new reference interval?
2. Verify a reference interval?
As recommended by the Clinical and Laboratory Standards Institute (CLSI)

Answer 1

1. 120
2. 20

Question 2

What is a priori sampling? (in establishing reference intervals)

Answer 2

When well defined inclusion/exclusion and partitioning criteria are established before reference individuals are selected.

Question 3

What is a posteriori sampling? (in establishing reference intervals)

Answer 3

Where exclusion and partitioning occur after sample collection and analysis.

Question 4

Analytic variability of the method used for measurement can impact reference intervals.
1. What 8 things should be reported?
2. What are 6 other things that need to be considered?

Answer 4

1- Methods used
- Between run analytical inprecision
- Limit of detection
- Linearity
- Recovery
- Reportable range
- Interference characteristics (H, I and L)
- Traceability

2- Instrument equipment and maintenance
- Equivalent normal operation
- Equivalent quality control procedures for reagents, calibration, controls and calculation methods
- Reagent lot-to-lot variability
- Instrument variability (if multiple used)
- Technologist variability

Question 5

What two methods are recommended for outlier removal prior to reference interval determination by the CLSI?

Answer 5

Dixon’s test or Tukey’s Method