1- Additives

Question 1

Tests affected by carry over of EDTA

Answer 1

• Ca
• PT/PTT
• Potassium and Sodium
• Alkaline phosphatase
• Serum Iron

This anticoagulant can beused for some biochemistry
but is not suitable for:
 Alkaline phosphatase –falsely decreases alkaline
phosphatase by bindingmagnesium.
 Potassium and sodium -due to the addition of potassium to the sample –falsely increases potassium levels
 Calcium and magnesium -these are chelated
(binded) by the EDTA.

Question 2

Tests affected by carry over of Heparin

Answer 2

• Coagulation Studies
• Sodium (Na Heparin tube)
• Lithium (Li Heparin tube)
• Blood urea nitrogen (Ammonium Heparin tube)
• Ammonium (ammonium Heparin tube)
• Some heparin tubes have a gel for separation
• Acid phosphatase

Accelerates the action of antithrombin and prevents
clot formation This anticoagulant is not
suitable for haematology test, calcium, sodium or lithium as the heparin alters the cell morphology

Question 3

Tests affected by carry over of Citrate

Answer 3

• Alkaline Phosphatase
• Calcium
• Phosphorous

Inhibits and decreases ALP
Binds to calcium

Question 4

Tests affected by carry over of Potassium Oxalate

Answer 4

• Potassium and calcium
• Acid and Alkaline Phosphatase
• Amylase
• PT/PTT
• LD
• RBC Morphology

oxalate damages cell membranes and causes abnormal RBC morphology. Oxalate interferes in enzyme reactions.

Question 5

Tests affected by carry over of Silica (clot activator)

Answer 5

• PT/PTT

Question 6

Tests affected by carry over of Sodium Fluoride

Answer 6

• Sodium

* Urea Nitrogen