Clinics and Departments

Laboratory Services

Lab Dept:

Coagulation

Test Name:

PTT, CIRCUIT

General Information

Lab Order Codes:

PTTC

Synonyms:

APTT – circuit; Partial Thromboplastin Time – circuit; Activated PTT – circuit

CPT Codes:

85730 – Thromboplastin time, partial (PTT); plasma or whole blood

Test Includes:

PTT Circuit reported in seconds.

Logistics

Test Indications:

Useful in monitoring/adjusting the amount of heparin being used in the external system during hemofiltration and extra corporeal membrane oxygenation (ECMO).

Lab Testing Sections:

Coagulation

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

2 hours

Special Instructions:

Patient’s with hematocrit levels >55% must have a special tube made to adjust for the hematocrit; contact the laboratory for special tube.

Specimen

Specimen Type:

Whole blood

Container:

Light Blue top tube (Buffered Na Citrate 3.2%)

Draw Volume:

1.8 mL or 2.7 mL blood (in appropriate sized tube)

Processed Volume:

1 mL (Minimum: 0.5 mL) plasma

Collection:

● Mix thoroughly by gentle inversion.

● Deliver immediately to the laboratory. Indicate when specimen is drawn from a line or a heparin lock.

Special Processing:

Lab staff: Centrifuge in Stat Spin for 5 minutes or 10 minutes at 3000 rpm at room temperature. For primary tube testing, leave plasma on cells OR remove plasma and place in a 4 mL plastic cup; allow for 100 mL of deadspace.

Test within:
● Four (4) hours when stored as plasma remaining in the capped tube above the packed cells 18 to 24C.
● Four (4) hours as plasma that has been separated from cells by centrifugation when stored when 2 to 8C or 18 to 24C.
● Two (2) weeks when stored -20C.
● Six (6) months when stored -70C (rapidly frozen).

● Plasma must be frozen if testing cannot be completed within four (4) hours.
● Frozen plasmas are thawed at 37C for three (3) minutes, test immediately.

Patient Preparation:

None

Sample Rejection:

Improper tube; clotted sample; underfilled tube, mislabeled or unlabeled specimens

Interpretive

Reference Range:

Approximately 1 – 1 times the patient’s peripheral PTT value.

Critical Values:

N/A

Limitations:

N/A

Methodology:

Micronized silica

References:

Harmening DH (1997) Clinical Hematology and Fundamentals of Hemostasis

Updates:

7/19/2006: Removed statement, "Do not transport by pneumatic tube".
8/20/2013: Updated specimen stability information.



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