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Laboratory Medicine

Test Directory / APTT Ratio

APTT Ratio

Citrated Plasma

TestAPTT Ratio
Common AbbreviationsAPR
Clinical IndicationUsed for patients on unfractionated heparin (UFH) therapy.
Specimen TypeBlood
Sample TypeCitrated Plasma
Minimum Volume1 x 3 mL (adult) 1 x 1 mL (paed) (citrated plasma must be filled to bottle line)
Special PrecautionsMust have a base-line coagulation screen prior to heparin therapy. Must not be used if APTT base-line is raised - discuss with Haematology Consultant.
Stability4-6 hours
Turnaround Time45 min (urgent) 3 hours (routine)
LaboratoryYork & Scarboroug
Reference IntervalTherapeutic range 1.5 to 2.5.
LimitationsHaemolysis, gross lipaemia, high haematocrit may interfere with measurement. Over or under filled samples cannot be used due to ratio between blood and citrate
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