Item Value
Test name Activated Partial Thromboplastin Time
Available Stat? Yes
Turn around times STAT 1 hour, Routine 4 hours
In House Availability Test available 24 hours per day 7 days per week
Performed by Parnassus, Mission Bay & Mt. Zion Hematology
Normal range
Age Normal range
Full term infant, 0-5 day old 25.0-60.0 seconds
Full term infant, 6 days-3 months 24.0-50.0 seconds
>3 months 22.6 - 34.5 seconds


An infant reference range has not been experimentally determined using our current PTT reagent. The PTTs of normal infants are longer than those of adults due to lower factor levels in the first months of life; the infant reference ranges provided (5 days, 3 months) are based on published literature (Ref: Andrew M et al. Blood 1987; 70-165). This publication further indicates that although trending longer, PTT values at 3 months may not differ statistically from adult values. If there is concern for clotting factor deficiency or inhibitor in an infant, factor activity assays should be requested if clinically indicated.
Container type Blue (2.7 mL) or Lt. Blue (1.8 mL) top filled to full extent of vacuum
Amount to Collect
Blue top 2.7 mL blood
Lt. Blue top 1.8 mL blood


Note: If hepabsorption is required draw a full Blue top (2.7 mL)
Collection Instructions 1. Check the expiration date on the label of the blue top vacutainer before drawing the patient.

2. For blood collection in a sodium citrate blue top, the tube must be filled to above the Minimum Fill Indicator on the tube. It is crucial to wait and allow the tube to stop filling before removing it from the needle.

3. With use of a butterfly needle, draw about 1 cc using a separate blue top to remove air from tubing, discard the first tube and then draw a second blue top tube filled to the full extent of the vacuum.

4. Tubes should not be filled past the Maximum Fill dashed line by either using a syringe or removing the tube cap.

For patients with Hct's ≥ 55% please contact Hematology (For Parnassus patients call 3-1747, for Mission Bay patients call 6-0194) to obtain blue top tubes with adjusted citrate volumes in order to maintain the proper citrate to plasma ratio for coagulation studies.
Sample type Citrated plasma

If you have additional questions regarding this test, please call: 415-353-1667