Protime Equal Mix

Performing Lab: Regions

3631

Sunquest: APTM; Protime 1:2 Dilution, PT Mix

PROX; PTMIX; PTNP

2.7 mL (in 3 mL tube) 3.2% Sodium Citrate Plasma (light blue-top) tube filled to fill line on the tube

1.0 mL plasma aliquot per test

1.0 mL platelet poor plasma (Frozen)

Processing:  Freeze an aliquot of platelet poor plasma at -20°C if not performed within 4 hours of collection
Centrifuge light blue-top tube for 15 minutes at approximately 1500 g within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet poor plasma into a new plastic vial. Plasma must be free of platelets (<10,000/mcl). Freeze immediately and ship on dry ice.
 

Transport processed samples frozen on Dry Ice

Frozen if > 4 hours old

Room Temperature: 4 hours       Refrigerated: 4 hours       Frozen: 72 hours at -20C or 2 weeks at -80C

Hemolyzed or Clotted Samples, Samples do not meet the minimum draw requirements, Samples exceed maximum draw requirements, Samples with hematocrit >55% not collected with the special tube. Samples from patients on Direct Xa inhibitors, thrombin inhibiotrs.

Daily

Same day.

If the patient’s hematocrit is greater than 55%, special tubes with less anticoagulant must be used for specimen collection

An equal mix with pooled plasma should normalize the PT. If the patient’s abnormal PT is due to a factor deficiency, the 1:2 mix should bring the PT into the normal range. Specific factor assays can then be done. If the PT mix does not normalize, an inhibitor/antibody should be considered, along with patient history.

Mixing equal amounts of normal plasma with patient plasma will correct an abnormal protime when it is caused by a factor deficiency (including Coumadin therapy). If the protime does not correct sufficiently, there may be an inhibitor or antibody present. In either case, the results of an equal mix will be a guide for further testing.