Interferences

There are a variety of different factors that can interfere with laboratory results. The following provides an overview of possible interferences.

Specimen Integrity Issues

Hemolysis

Hemolysis can interfere directly with lab results (due to the release of red blood cell components) or indirectly by affecting

• May be due to patient's condition (e.g., hemolytic anemia, autoimmune conditions, certain drugs, etc.)
• May be due to improper specimen collection (e.g., too much force during venipuncture due to small needle gauge or pulling too hard on syringe, slow draws, excess damage to tissue during venipuncture, excessive mixing, etc.)

Tests most affected by hemolysis include:

• Potassium
• ALP
• LDH
• RBC
• Hemoglobin
• Hematocrit

Lipemia

• Cloudiness of sample due to lipemia affects photometric methods
• May be caused by recent fatty meals or be due to a patient's condition
• Lipemia can be removed by ultracentrifugation of samples
  • Do not ultracentrifuge lipid, cholesterol, triglyceride, etc. tests as this removes the fats

Other Factors

• Quantity not sufficient
  • Insufficient sample volumes may cause aspiration errors and cause false results
• Diluted specimen
  • Dilution of the specimen can be the result of improper collection (e.g., saline or other products from collection above IV lines) or due to adulteration
  • These specimens will generally show decreased results due to a dilutional effect
  • Serum/plasma may appear very pale, and the ratio of red blood cells to plasma will be off (significantly more plasma than red blood cells)
  • Multiple different results may be affected (e.g., chemistry and hematology results, multiple analytes, etc.)
  • Certain tests may be affected more depending on the diluting material
    • Contamination from heparinized lines will falsely prolong coagulation results
• Contaminated specimen
  • EDTA contamination may cause falsely decreased calcium and increased potassium
• Biotin
  • Biotin (also known as Vitamin B7, Vitamin H, or coenzyme R) may interfere with biotin-based immunoassays, causing false positive results