### Description

Lockwood et al used 2 equations for evaluating red blood cell recovery following freezing, thawing and washing a blood product. The first equation estimates the recovery after thawing a frozen unit, and the second the recovery after completing the wash processing.

Parameters to measure:

(1) total volume of the product after thawing in dL

(2) hemoglobin of the product after thawing

(3) hemoglobin of the supernatant (glycerol rich fluid)

(4) hematocrit of the product after thawing

(5) hemoglobin of the product after washing completed

(6) total volume of product after washing in dL

percent freeze-thaw recovery =

= 100 * ((hemoglobin concentration of the whole product after thawing in g/dL) - ((1 - (hematocrit as a decimal fraction)) * (hemoglobin concentration of the supernatant fluid in g/dL))) / (hemoglobin concentration of the whole product after thawing in g/dL)

percent recovery of the thawed product after completing freeze-thaw-wash =

= 100 * (total hemoglobin of the washed and deglycerolized product in grams) / (total hemoglobin of the thawed unit in grams) =

= 100 * (hemoglobin concentration in g/dL after washing) * (volume of product in dL after washing) / ((hemoglobin concentration in g/dL before washing) * (volume of thawed product in dL))

where:

• dL indicates deciliter or 0.1 liters.

• The total hemoglobin in the thawed product is the same as the product before it was frozen (not before glycerol added). If there is hemolysis then free hemoglobin will be present in the supernatant.

• (1 - (hematocrit as decimal fraction)) indicates the amount of supernatant present in the product.

• In trying to understand the first equation, it makes sense as a ratio of total hemoglobin. This requires multiplying both numerator and denominator by the total volume in deciliters. The ((1 - (hematocrit)) * (hemoglobin in supernatant)) indicates the amount of hemoglobin lost due to hemolysis.

Although not included as one of the equations, the percent recovery based on the original blood product can be calculated:

percent recovery of the original product after completing freeze-thaw-wash =

= 100 * (hemoglobin concentration in g/dL after washing) * (volume of product in dL after washing) / ((hemoglobin concentration in g/dL of original product) * (volume of original product in dL))