Assay

Thrombotic Screen

Key Words

Thrombophilia Screen, Protein C, Protein S, Activated Protein C Resistance, APCR, Factor V Leiden, FVL, Antithrombin, AT, Prothrombin G20210A

Specimen Collection

5x 3.0ml Citrate (Green lid). Equivalent volume with 1.4ml Citrate for paediatric (Green lid) - Discuss with laboratory. Fill to mark. A Lupus Anticoagulant Screen will also be performed as standard, but a Thrombotic Screen may be indicated without one in some circumstances. Discuss with laboratory regarding sample requirements if unsure. Molecular investigations by PCR will be performed if APCR of Thrombotic Screen is abnormal. Samples will be processed up to 24 hours from the time of collection. Due to the nature of the assay, this test cannot easily be added on to routine coagulation requests sent with a single sample, UNLESS the assay is being performed on the day of receipt (which only occurs once every two weeks). Contact the laboratory before requesting this test as an add-on.

Turnaround time

1 Month

Test indications

Investigation of inherited thrombophilia or fertility screen. To be requested by consultant general practitioner, or registrar.

Interferences

Recent thrombosis, lipaemia, haemolysis, anticoagulants, pregnancy and up to 3 months post-obstetric event.

Reference Range

See table below. Adult reference ranges from reagent manufacturer's package inserts. Paediatric reference ranges from: Williams, M., Chalmers, E. and Gibson, B. (2002). The investigation and management of neonatal haemostasis and thrombosis. British Journal of Haematology, 119(2), pp.295-309.

Minimum retesting interval

Lupus Anticoagulant Screen requests made within 70 days of a previous request on a patient are intervened. Thrombotic Screen requests made where historic results exist on a patient are intervened.

TEST

AGE / GENDER

REFERENCE RANGE

UNITS

Protein C

Full term up to 1 day

26 - 44

%

Full term up to 5 days

30 – 53

Full term up to 1 month

32 – 54

Full term up to 3 months

41 – 67

Full term up to 6 months

48 – 70

6 months - Adult

70 - 140

Protein S

Full term up to 1 day

24 - 48

%

Full term up to 5 days

36 – 64

Full term up to 1 month

48 – 78

Full term up to 6 months

70 – 102

Male 6 months - Adult

74.1 - 146.1

Female 6 months - Adult (affected by pregnancy)

54.7 - 123.7

Antithrombin

Full term up to 5 days

53 - 80

%

Full term up to 1 month

63 – 93

Full term up to 3 months

85 – 110

3 months - Adult

83 - 128

Activated Protein C resistance (APCR)

Full term up to 6 months    

2.61 - 3.32

Ratio

6 months – Adult

2.20 - 3.32