5971 Thrombotic Risk Evaluation 2

Components
NAME METHOD REFERENCE RANGE UNITS
APCR Ratio CLOT DET  > 2.22   
APCR Interpretation   By Report   
Antithrombin III Functional CHROM  75 - 125  % 
Fibrinogen CLOT DET  185 - 434  mg/dL 
Homocysteine UltraQuant ENZYMATIC  view ref range  umol/L 
Protein C Activity CHROM  70 - 140  % 
Protein S Activity CLOT DET  65 - 140  % 


Specimen Requirements
TYPE VOLUME TEMPERATURE INSTRUCTIONS
PRIMARY
1 Plasma Citrated 4 (2) mL   Frozen - 14 Day(s) See COLLECTION INSTRUCTIONS for platelet-poor plasma. 
2 Serum 2 (1) mL   Frozen - 2 Month(s)  


Clinical utility
APCR is the most common inherited risk factor for venous thrombosis. It is a screening test for Factor V Leiden. Elevated homocysteine levels can be a risk factor for atherosclerosis and thrombosis. Elevated homocysteine levels are seen in folate deficiency, as well as in the presence of MTHFR C677 T polymorphism. Elevated fibrinogen levels have been linked to venous thrombosis. ATIII, Protein C and Protein S are less common inherited risk factors for venous thrombosis.


Collection Instruction
Patient should be at rest. Sensitivity and
specificity for FV Leiden are not affected by Coumadin. Assay
allows for analysis of plasma from heparinized patients at
levels < or equal to 1 IU/mL, unfractionated or LMW. Plasma from
patients with high APA inhibitor activity may give an abnormal
clotting time.
Avoid contact activation of samples since this may lead to
activation of FV and FVIII.
Hirudin anticoagulant interferes with Antithrombin III Functional
assay. Inaccurate results might be obtained in its presence due
to inhibitory action on thrombin.
Instructions for platelet-poor plasma:
Draw red top tube to remove tissue fluid contamination and discard.
Draw blood into a buffered citrate collection tube (light blue
top) filled to proper level.
Blood-to-anticoagulant ratio should be 9:1; inadequate
filling of collection device will decrease ratio and
may lead to inaccurate results.
Adjust final citrate concentration in blood
of patients with hematocrit values above 0.55 (55%). For
hematocrits below 20%, there are no current data to
support a recommendation for adjusting citrate concentration.
Needle gauge may be between 19-22 (pediatric patients 21-23 gauge).
Gently invert tube 6 times. Process immediately.
Centrifuge for 15 min at 2500 x g.
Remove plasma using a plastic pipette and transfer to a new tube.
Repeat centrifugation at 2500 x g for 15 min.
Dispense plasma into 2 or more plastic tubes using a plastic
transfer pipette.
Freeze immediately. Stable for 2 months at -20 C and 6 months at -70
C.
Specimen must remain frozen at all times.
Specimen should not be submitted if it is hemolyzed, microclots
are present, tube is less than 90% filled or a specimen with
hematocrit >55% is collected without anticoagulant adjustment.
Homocysteine: Centrifuge serum within one hour
of collection. Slightly higher values are observed in non-fasting
patients.


Reported: Next day

CPT Code: 83090, 85300, 85303, 85306, 85307x2, 85384

Notes: Protein C and Protein S are decreased in Coumadin therapy, DIC or extensive thrombosis. Lipoprotein (a), #3446, an additional risk factor for thrombosis, can be ordered separately.