Laboratory: Clinical Biochemistry
Test Name:
Test Code: TIWB
Clinical Information:
Only available in rural Manitoba.  For WRHA and Westman Lab see TROPONIN T, HIGH-SENSITIVITY (hsTnT) - (P)
Fresh heparinized whole blood or plasma samples collected in syringes or evacuated tubes containing lithium or sodium heparin.  Collection tubes must be filled.   Failure to completely fill tubes may cause falsely elevated results when plasma is used. Mix blood and anticoagulant by inverting a tube gently at least ten times.
If sample will not be analyzed within 30 minutes of collection, sample should be centrifuged promptly and plasma must be used for analysis.  Plasma samples are stable for 24 hours at 2-8 °C and for 12 months at -20 °C (freeze only once).
State whether the sample is venous or arterial.

Interferences:  Heparin at 90 U/mL can decrease the cTnI level by approximately 20%

See: Algorithm for Chest Pain with Cardiac Features
Collection Devices:
Specimen Required: Skin puncture:  not recommended.
Venipuncture: lithium or sodium heparin collection tubes and disposable transfer device (e.g. 1 cc syringe and a 16 to 20 gauge needle).  Alternately, a plain syringe or plain collection tube and disposable transfer device can be used if the sample is tested within one minute of patient draw.

Only available at sites which perform iStat testing onsite.
Reference Values:
Troponin is considered negative: (when measured  ≥ 6-8 hrs after onset of chest pain)  
Negative: < 0.08 µg/L  OR
Negative:  ≥ 0.08 µg/L and not rising on 2 samples measured at least 2 hrs apart
and in context of alternate etiology for elevated troponin

Note:  Reference ranges are specific to the Abbott iStat (POC instrument)
Turn around time (TAT): < 60 minutes
See Also:
More Information:
Gross hemolysed samples: can cause a decreased alkaline phosphatase activity, resulting in decreased detection of cTnI, increased assay backgrounds, and/or quality check codes.
Partially filled tubes: Failure to completely fill tubes may cause falsely elevated results when plasma is used.
Partially clotted samples: can result in elevated cTnI results above the reference range, as well as quality check code errors. To prevent this from occurring, upon drawing the whole blood sample into a heparinized collection tube, the sample should be inverted gently at least 10 times to ensure even dissolution of the heparin anticoagulant.