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Test Code PTT Activated Partial Thromboplastin Time (APTT), LAB325

Specimen Requirements

Container/Tube:

Preferred: Full blue-top (sodium citrate) 1.8 mL tube-Hemolyzed or short draw specimen is not acceptable.
Specimen Volume:
 0.5 mL sodium citrate plasma

Stability: Centrifuged specimens at 2-4°C or at 18-24°C must be tested within 4 hours of specimen collection.

Collection Instructions: Centrifuge immediately after draw. Forward promptly. If there is a delay in transport of >4 hours or if mailing time exceeds 4 hours, spin down, remove plasma from cells and freeze immediately in plastic vial. Send specimen frozen. Specimen stability is ≤2 weeks when frozen at -20° C.

 

NOTE:  Patients with a hematocrit of >55% must be recollected using an altered amount of sodium citrate.

Reference Values

 

 

PTT (seconds)

Age

Low

High

Critical

0-1 day

30.8

48.0

≥78.0

2-5 days

25.0

52.7

≥78.0

6-29 days

25.2

48.6

≥78.0

1-3 months

23.8

44.2

≥68.0

4-11 months

27.7

37.8

≥68.0

1 – 5 years

23.3

32.0

≥58.0

6 – 10 years

25.2

32.0

≥58.0

11 – 16 years

25.2

32.9

≥58.0

>17 year

26.2

35.6

≥62.0

 

Performing Laboratory

St. Luke's Hospital Cedar Rapids

Day(s) Test Set Up

Monday through Sunday

Useful For

The activated partial thromboplastin time test is sensitive to all coagulation factors except factors VII and XIII, so it is an effective screening test for the entire intrinsic coagulation system.

Methodology

Clot Based Assay

Test Classification and CPT Coding

85730