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Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

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PARTIAL THROMBOPLASTIN TIME, ACTIVATED (APTT)

Item Value
Approval req'd? no
Available Stat? Yes
Test code PTT
Performed by? Hematology
Sendout? no
Price range $
In House Availability Stat or routine, 24 hours/7days
Principle The test involves activating the intrinsic clotting factors in plasma with micronized silica (suspended with a standard concentration of platelet phospholipids) and clotting the mixture with CaCl2.
Interpretation APTT will be prolonged with acquired or congenital deficiencies in the intrinsic clotting system. It is prolonged in proportion to heparin concentration in plasma. For monitoring therapy with unfractionated heparin (UFH), it is important to obtain a baseline APTT. The suggested therapeutic range is 90 – 108 seconds with the new APTT reagent (as of 8/31/17). This range may change with future APTT reagents. The up to date therapeutic range for UFH therapy is listed with each APTT result in the electronic medical record (LCR).
Container type blue top tube
Amount to Collect full tube (2.7 mL blood; pediatric: 1.8 mL)
Collection Instructions See Coagulation Procedures for instructions on collecting coagulation specimens.
Sample type Citrated plasma
Special instructions Indicate use of anticoagulant drugs on requisition slip.
Normal range ADULTS: < 37.6 seconds (Current range; changes with new lot of reagents.)

Pediatric reference ranges for APTT have not been established at SFGH. In general, the neonatal range is 20 – 50% higher than in adults, while children from the age of 1 year to adolescence have slightly shorter APTTs (up to 10% shorter) than adults.
Critical values > 68.9 seconds
Synonyms APTT;
Stability 4 hours
References 1. Triplett, D. and Harms, C.S. Procedures for the Coagulation Laboratory. Chicago, IL: Am. Soc. of Clin. Path., 1982.

2. STA Compact Operator Manual. Diagnostica STAGO. February 2001.

3. Gottfried, E.L. and Peterson, P. The Effects of Inaccurate Sample Volume on Prothrombin Time (PT) and Activated Partial thromboplastin Time (APTT). Thrombosis and Haemostasis 47:101-103, 1982.

4. Reneke, J., et al., Prolonged Prothrombin Time and Activated Partial Thromboplastin Time Due to Underfilled Specimen Tubes. Amer. Journal of Clin. Path., Vol. 109: 754-57, 1998.

5. Adcock, D., et al. The effect of time and temperature variables on routine coagulation tests. Blood Coagul Fibrinolysis, 4: 463-470, 1998.
CPT coding 85730
Last Updated 8/31/2017 8:51:43 AM
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