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Silica Clotting Time (SCT)

Important Note

Included as part of the Lupus Anticoagulant Panel

Specimen Collection Information

Specimen Minimum Test Volume Container Special Handling
Blood 1.5 ML  

Specimen Transport Temperature

Double spin, separate, and freeze

Specimen Stability

4 hours

Additional Specimen Instructions


2.7 mL Sodium Citrate tube filled to the line



Blue top tubes must be filled within 10% of stated volume. A discard tube must be used if a citrate tube is to be drawn using a winged blood collection set.  It is important to remove air from the blood collection set to ensure the proper blood volume is obtained in the coag tube.


If the patient has a known hematocrit >55%, please contact the coagulation lab for an adjusted collection tube before drawing the blood.

Reference Ranges / Critical Values

Assay Gender Age Range Normal Range Critical Values Units
Silica Clotting Time All 0 Minutes – 150 Years <1.16   ratio

Interpretive Data

Assay Display Interpretive Data
Silica Clotting Time A result greater than 1.16 TR is consistent with the presence of lupus anticoagulant. Values of 1.16 to 1.24 in this assay are not definitively positive or negative for the presence of a lupus anticoagulant. The SCT ratio may be falsely elevated in patients on anticoagulants especially heparins and direct oral anticoagulants. An abnormal test result in an anticoagulated patient must therefore be interpreted with caution and repeat testing after discontinuing anticoagulation may be appropriate.

Performing Lab Section