Confirmation and characterization of protein S (PS) deficiency: C4b-binding protein elevates as an acute phase protein that may lead to enhanced protein S binding and decreased free protein S levels.

Lt blue Sodium citrate (NaCit), 2.7mL

• Do not draw from an arm with a heparin lock or heparinized catheter
• Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.
• Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.
• The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood.
• A discard tube is not required prior to collection of coagulation samples, except when using a winged blood collection device (ie, "butterfly"), in which case a discard tube should be used. When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes.
• Immediately following collection, mix sample thoroughly by gently inverting 8 - 10, times to prevent clotting
• Any tube containing an alternate anticoagulant should be collected after the blue-top tube.
• Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes.

Prepare platelet poor plasma (PPP):

1. Spin for 10 minutes 
2. Carefully remove 2/3 of the plasma using a plastic transfer pipette, being careful not to disturb the cells.
3. Deliver to a plastic transport tube, cap, and respin for 10 minutes.
4. Use a second plastic pipette to remove the plasma, staying clear of the platelets at the bottom of the tube.
5. Transfer the plasma into a Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp), labelled as PPP
6. Freeze

Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp)

Frozen (strict)

Ambient - 8 hours

Enzyme-linked immunosorbent assay (ELISA)

C4bBP levels range from 60 - 150%

• Adult levels of C4bBP are generally reached at six months of age
• Levels are generally undetectable in the neonate