American Association for Clinical Chemistry
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NACB - Scientific Shorts
NACB - Scientific Shorts (formerly NACB Blog)
By Douglas F. Stickle, PhD, DABCC, FACB
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My not-very-long experience as a POCT director is that large things can drop unexpectedly into the realm of the POCT program from great administrative heights. Such was a recent occurrence at our institution regarding startup of thromboelastography (TEG). TEG is not unknown in POCT, and educational sessions regarding TEG have been part of past AACC meetings. Nonetheless, the topic is still somewhat esoteric among clinical biochemists. I give a short outline of TEG here, and outline certain challenges in its implementation as POCT.
The clinical use of TEG is primarily to assess bleeding risk and to guide short-term interventions in the forms of drug administration to promote or inhibit or reverse clot formation, or administration of plasma, platelets or fibrinogen. Its use has been described in surgery, transfusion, trauma, and obstetrics [1].
The TEG method was developed more than sixty years ago [2]. The device mechanically tracks clotting of a fresh blood sample. A circular sample cup is rotated slowly back and forth through a small angle. A disk suspended in the sample tracks this motion only as the formation and mechanical characteristics of a clot allow transmission of motion from the outer cup to the disk through the sample. A graph of the back and forth angular motion of the suspended disk provides characterization parameters such as time to initiation of clot, rate of clot formation after initiation, extent or strength of clot formation, and fibrinolytic activity. ROTEM (rotational thromboelastometer) is a variant on this technique, but with motion impelled to the suspended inner disk rather than to the outer disk. ROTEM parameters parallel those of TEG, although measurements between the two techniques are not directly comparable [3]. A complete TEG graph to include eventual fibrinolytic activity can take more than an hour to complete for normal samples.
Presumably (and according to attestation of others) an experienced user can be adept at making appropriate intervention decisions in an otherwise-unachievable timely fashion when TEG is used. However, standardizations of methods and of practice are not firmly established [4]. At present, TEG is not used uniformly as a standard of care across surgical practices performing the same procedures, even within the same institution; its use depends on preference, experience and desires of a given surgical team.
TEG rates as moderate complexity testing. In most settings, this means that pathology staff will likely be the necessary license holders. In our case, testing is proposed to be performed by OR staff as POCT in the OR, but this is yet untested. The regulatory requirements of such testing (maintenance, QC, PT) will put such users squarely in the role of laboratorians, which will be very unfamiliar territory for them. The prospect of routine performance of QC alone, given the time needed for a complete sample run, likely dictates a significant change to OR staff work flow. Alternatives may be to staff with lab personnel on an ad-hoc basis (a very costly prospect), or to have the testing performed in the laboratory with a graphical output visible in the OR in real time. Readers are invited to comment about their experience in setting up TEG.

 

 

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About the Author
Douglas F. Stickle, PhD, DABCC, FACB
Douglas F. Stickle, PhD, DABCC, FACB 
 

References

1. Luddington RJ. Thrombelastography/thromboelastometry. Clin Lab Haematol. 2005;27:81-90.

2. Hartert H. [Thrombelastography, a method for physical analysis of blood coagulation.] Z Gesamte Exp Med 1951;117:189-203.

3. Kitchen DP, Kitchen S, Jennings I, Woods T, Walker I. Quality assurance and quality control of thromboelastography and rotational thromboelastometry: the UK NEQAS for blood coagulation experience. Semin Thromb Hemost 2010;36:757-63.

4. Chitlur M, Lusher J. Standardization of thromboelastography: values and challenges. Semin Thromb Hemost 2010;36:701-11.