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Laboratory Test Reference Guide

Laboratory Information

Test Name

Protein S (Free)

External Price (excl. GST)



Specimen Collection

Adult Specimen

2.7 mL sodium citrate tube (light blue)

Paediatric Specimen

1.8 ml paediatric sodium citrate tube (light blue)

Instructions for Referral to Waikato Lab

Aliquot Instructions

500uL double spun platelet poor plasma

Aliquot Transport

Send frozen

Test Information



Test Availability

Mon - Fri, 0800 - 1630 excl. Public Holidays

Reference Interval

67 – 135% (males)
56 – 135% (females)

Diagnostic Use Or Instructions

In plasma, protein S circulates both free (~40%) and in a complex with C4b binding protein (~60%). Only the free form of protein S can function as an anticoagulant. Protein S levels may be reduced due to a congenital deficiency, an acquired decrease in the protein level (e.g. vitamin K deficiency, liver disease or warfarin therapy), or a shift of free protein to the bound form during an acute phase response with elevated C4b binding protein. A congenital deficiency in protein S may lead to a recurrent thrombotic tendency

Minimum Volume

500uL double spun platelet poor plasma

Electronic Information

Registration Code


HL7Mapping Code