Calculations In Finding Compatible Blood

Question 1

What is the formula used to solve for the number of units to crossmatch

Answer 1

no. of units crossmatched=number of units needed/negative frequency of antigen 1*negative frequency of antigen 2

Question 2

Using the formula from the first question, solve the ff. problem:
Anti-K and anti-c were found in a patient with colon cancer. How many units of red cells would need to be screened to find two compatible units for surgery? The antigen negative frequency for K and c are 0.91 and 0.20 respectively

Answer 2

xmatch= 2 units/(0.91*0.20)

= 2/0.182 =10.989 or 11 units

Question 3

A patient anti-K and anti-Jka in her plasma needs 2 units of RBC for surgery. How many group specific units would need to be screened to find units of RBC. The frequency of Jk (a+) is 77% and K+ is 10%

Answer 3

crossmatch = 2 units/0.23*0.90

Get negative frequency::
100-77=23
100-10=90

= 2/0.207=9.662 or 10 units