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Test Code LAB2978 Discordant Heparin Panel

Clinical System Name

Discordant Heparin Panel

Synonyms

LAB2978

Heparin PTT, Corrected

Sample Requirements

Specimen: Whole Blood

Container(s): Lt Blue/Citrate

Required Vol: 1.8 mL tube

Minimum Vol: N

 

Note: Preferred method of collection is venipuncture with vacuum fill. Test results are affected by incorrect blood volume, note fill line on tube.

Use of a Vascular Access Device for the collection of coag testing is not recommended. If this method is used, it requires a 5 mL waste volume, 3 mL for size 2 French catheter or smaller. Blood must be transferred to the Lt Blue/Citrate tube by use of a blood transfer device to ensure proper fill.

Specimen should be centrifuged within 1 hour of collection.

Processing Instructions

Main Campus CPA: Core Technologist will process specimen. Deliver blood directly to Core Coag bench.

 

Reject due to: Clotted, Insufficient quantity (underfill), or Improper collection (overfill).

Spin: Y

Aliquot: Y

Storage location: Core 14 Freezer ( -70 C).

 

Core Technologist: Specimen should be centrifuged within 1 hour of collection. Spin whole blood, remove plasma. Transfer upper 3/4 layer of plasma to plastic tube affixed with large computer label.

 

Off-site collection: Preferred method of collection is venipuncture with vacuum fill. Test results are affected by incorrect blood volume, note the fill line on the tube. Use of a Vascular Access Device for the collection of coag testing is not recommended. If this method is used it requires a 5 mL waste volume; 3 mL for size 2 French catheter or smaller. Blood must be transferred to the Lt Blue/Citrate tube by use of the blood transfer device.

 

Specimen should be centrifuged within 1 hour of collection. Double spin, transfer upper 3/4 layer of plasma to plastic tube affixed with large computer label. Freeze until solid one aliquot of 1.0 mL plasma in plastic tube at -70C (preferred) or -20C.

 

Non-Children's Hospital Off-site collection: Ship completely frozen on dry ice.

 

Children's Regional Clinics: Ship completely frozen in frozen Nalgene Labtop cooler with ice pack inside an insulated soft cooler.

Stability

Specimen Type Temperature Time
Citrated platelet-poor plasma Room temp ≤4 h
  Refrigerated N
  Frozen   -20 C or -70 C ≤3 m

 

Availability

STAT Performed TAT
Y

Daily

1 h

 

Performing Laboratory

Seattle Children's Laboratory    

 

Department

Department:  Coagulation

Phone Number: 206 987-2617 (Client Services)

CPT Codes

85730

Methodology

Method: Electromagnetic mechanical clot detection system by STA-R MAX

Analytical Volume: 1 mL plasma

Limitations: Method is affected by improper collection, processing, and storage.

High hematocrit greater than or equal to 56% requires a citrate adjusted tube.

Reference Range

Age Baseline APTT
Newborn - 3 Months 25 - 40 sec
3 Months and Older 25 - 35 sec

There are no established reference ranges for premature newborns.

Description

PTTs for patients on heparin that do not agree with heparin levels measured by the anti-Xa heparin activity assay are termed discordant. The most common cause of discordant PTTs is a prolonged baseline PTT that alters the response of the PTT to heparin producing falsely high heparin PTTs compared to the anti-Xa heparin activity. Reasons for a prolonged baseline PTT include factor deficiency and deficiency in contact activation, including contact factor deficiencies and phospholipid neutralization by lupus inhibitors. In most cases the heparin activity result is a better indication of the anticoagulant effect of unfractionated heparin therapy as it is sensitive to only heparin and antithrombin levels in plasma. The heparin activity result, however, can be falsely lowered by increased levels of bilirubin and/or hemoglobin. With high levels of hemolysis and/or icterus the anti-Xa heparin activity assay can fail due to saturation of the spectrophotometer, leaving the PTT as the only option for UFH monitoring in these patients.

 

To adjust for the effect of prolonged baseline PTTs, a baseline-corrected PTT is calculated. The baseline PTT on heparin is determined using automated heparin neutralization with protamine but is not reported.

 

The Discordant Heparin Panel reports two results

1) Patients original PTT on heparin = PTT

2) Baseline-corrected PTT on heparin = Heparin PTT, Corrected

 

If the baseline PTT is normal, the original PTT and Heparin PTT, Corrected are close to the same value indicating concordance. If the original PTT and Heparin PTT, Corrected are substantially different it indicates PTT discordance and the Heparin PTT, Corrected should be used for heparin monitoring with a PTT heparin therapeutic range of 66 to 108 sec.

Note: Heparin PTT, Corrected - calculation unavailable for PTT>200 seconds.

Critical Values

≥ 150 seconds.

 

Heparin PTT, Corrected, Therapeutic Range

66 – 108 sec