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Case A6 - Answer (Panel 3- Question #1)
 

TraQ Program of the BC PBCO

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Monday, 25 September 2017

Case A6 - Answer (Panel 3- Question #1)

 

Anti-E has been confirmed with an acceptable probability. There are more than three positive cells and three negative cells (meeting the minimum p value of 0.05).

Online p value calculator

See this online tool for calculating p values - Enter values as follows:

  1. Change Outcome 1 to negative and Outcome 2 to positive
  2. Change Group 1 to antigen-neg (e.g., K-) and Group 2 to antigen-pos (e.g., K+)
  3. The 2 x 2 table would look like this (hypothetical example):
Negative Positive
K- 9 0
K+ 0 1
  1. Choose Fisher's exact test
  2. Use a one tailed test  - A one-tail p value is appropriate only when previous data or common sense tell you that a difference, if any, can only go in one direction. Obviously, with antibody identification, we expect cells that are antigen-positive to react (and vice versa).
  3. Hit the calculate button.

Caution #1: Statistical calculations do not substitute for carefully examining serologic test results. It is critical to consider p values as just another tool. If acceptable, they provide additional converging evidence to support the conclusion regarding which antibody has been identified.

Caution #2: With complex antibody combinations, some blood banks prefer a minimum p value of 0.01 as an added measure of probability.

 

 

Last modified on Tuesday, 12 July 2011 14:38