Salting Out

The information I received in discovery regarding how the blood was obtained, handled and analyzed is not complete.   Without complete information it is impossible to rely upon the results.

The discovery material I received did include toxicology worksheet #1 which indicates that 2 grey top tubes were received by the laboratory.  The worksheet indicates that they were 10 milliliter tubes; however, the volume received, according to the worksheet, was only 14 milliliters.  The worksheet also noted that the tubes contained sodium fluoride which is a salt.

The amount of sodium fluoride in 10 milliliter grey top tubes is meant to be mixed with 10 milliliters of blood.  In this case, these tubes were deficient in the amount of blood.   This most commonly occurs due to loss of vacuum in the tubes.  In any case, the excess salt, sodium fluoride, produces what is called “salting out”.

Salting out occurs in the presence of excess salt.  The excess salt causes precipitation of the protein in the blood. Without these proteins the analyte is closer to serum and contains precipitated proteins.  This results in an erroneous elevation of the results. Since the results are unreliable, and it is not possible to quantify a degree of unreliability, the analysis of the specimen is invalid.