Gross errors made by routine blood sampling from two sites using a tourniquet applied at different positions

Area of Science:

• Clinical Biochemistry
• Laboratory Medicine

Background:

• Venous stasis from tourniquet application can alter blood sample composition.
• Accurate laboratory results depend on minimizing pre-analytical variables.

Purpose of the Study:

• To evaluate the impact of tourniquet application and sampling site on serum constituents.
• To assess the effect of sequential blood sampling on analyte concentrations.

Main Methods:

• Serum protein, calcium, and magnesium were measured in 31 healthy individuals.
• Venous stasis (3-min) was induced using a standardized tourniquet at various arm sites.
• Blood samples were collected from different arm locations and in series.

Main Results:

• Tourniquet application led to a 5-13% increase in serum protein concentrations.
• Blood drawn from the cubital vein showed greater hemoconcentration than distal samples.
• Sequential sampling resulted in a progressive 5-10% increase in measured analytes per tube.

Conclusions:

• Standardized tourniquet use and pre-sampling release do not eliminate venipuncture-induced errors.
• Adjusting results based on serum protein levels can help minimize these analytical errors.