A number of devices for point-of care testing of coagulation are now available and of these, the TEG® thromboelastograph (Haemoscope Corporation, Niles, IL, USA; Fig. 1) and the ROTEM® thromboelastometer (Pentapharm GmbH, Munich, Germany; Fig. 2) systems are amongst the best known. Both measure coagulation by assessing the shear elasticity of blood as it clots; the principles have been described elsewhere  but in brief, both employ a vertical pin held in the blood sample, contained within a cup or cuvette. In the TEG®, the cup oscillates clockwise and anticlockwise and as the blood clots, fibrin strands and platelet aggregates form between the pin and the inner walls of the cup, resulting in torque on the pin that is monitored and converted to an electrical signal. In the ROTEM®, an oscillatory force is applied to the pin and the cuvette is held stationary; as the blood clots, the extent of the pin’s actual oscillation is reduced and this is measured by the angle of deflection of a beam of light directed at the pin. We were interested in ‘road testing’ both devices with a view to a possible purchase, and here present our findings as an aid to other departments undergoing a similar process.
We have evaluated the TEG® thromboelastograph and the ROTEM® thromboelastometer, two point-of-care devices that measure blood coagulation. During a one-week period, seven consultant anaesthetists, one consultant haematologist, one associate specialist anaesthetist and two senior trainee anaesthetists were trained by the manufacturers and set up, calibrated and used both systems, after which their views were obtained and specific technical/support information was sought from the manufacturers using a questionnaire. Although the devices shared common features, they differed in complexity and aspects of ease of use, and in their purchase and running costs.
Both devices were installed on our labour ward for the same one-week period, during which time the UK representatives of both were present to train staff and provide support. During the trial period, seven consultant anaesthetists, one consultant haematologist, one associate specialist anaesthetist and two senior trainee anaesthetists participated in the evaluation, which included setting up/calibrating the machines and running tests on volunteer blood samples given by certain of the evaluators. (The Local Research Ethics Committee chairman was approached for advice before evaluation and considered a formal application unnecessary. All participants were aware of the implications of testing including issues around confidentiality). Assessment was semi-structured in that the features of the devices were categorised as indicated in the Table and opinions sought from all participants, both verbal and written. Following the trial period, a questionnaire was sent to the two companies to seek specific technical and support information.
The information supplied by the manufacturers (correct as of August 2008) and the overall opinions/comments of the evaluators are shown in Table 1.
|Description||Each 2-channel unit 29 × 19 × 23 cm;* separate computer and colour inkjet printer supplied. Runs in Windows XP®||57 × 37 × 57 cm; integral computer with touch-sensitive screen. Printer supplied at ∼£68 extra. Runs in Linux|
|Requirements for siting||Electrical point ± network point Level workbench; vibration free||Electrical point ± network point|
|Warm-up time||From ‘cold’ < 5 min; from ‘standby’ nil||From ‘cold’ 5–15 min; from ‘standby’ 1 min|
|Calibration/quality control (QC)||Daily checks: level positioning and machine check (both 2 min; no cost)||Constantly running internal QC; no daily test required (no cost)|
|No extra weekly testing required||Weekly formal QC required (∼£22; ∼30 min)|
|Monthly QC required (∼£17; ∼20 min)||No extra monthly testing required|
|If QC out of range: repeat test; contact office; further action depends on contract||As for TEG®|
|Tests/reagents||‘Routine’ test must be run within 4 min if sample is not anticoagulated (if citrated sample wait 30 min; must add calcium)||Advised to run two tests, INTEM and EXTEM (test internal and external pathways), for each patient. Citrated sample always used but may be used immediately|
|Other tests possible: heparinase, functional fibrinogen, platelet mapping. Can detect effect of low molecular weight heparin||Other tests possible as for TEG® except for platelet mapping. Cannot detect effect of low molecular weight heparin|
|Single-use vials used for all tests; shelf life 6–12 months||Multi-use vials used (though may be replaced by single-use); shelf life once opened 8–30 days depending on the test.|
|Pipettes||Manual pipettes required, 10–360 μl||Automatic pipette; 2 × 20 μl reagent per test|
|Reference ranges||Able to set own ranges and/or add two sets of ranges||Able to set own ranges|
|Results||Can superimpose results, set obligatory fields, set automatic backup, or export to xls format||Can superimpose results, set obligatory fields, set automatic backup, or export to xls/txt/jpeg formats|
|Output via USB port or networked (wireless connectivity possible)||Output via USB port or networked (wireless connectivity not currently possible)|
|List price||£13 500 (two channel unit, analyser, PC/laptop, printer, software, cables, pipettes, 8+ days’ on-site training, 1-year guarantee and on-site servicing)|
£26 000 (4 channel unit + as above)
|£21 662 (standard 4 channel, integrated PC, analyser, monitor, software, cables, pipettes, 3 days’ on-site training, 2-year guarantee and on-site servicing)|
|Cost of reagents||Kaolin vials (for standard testing) £2.52 each; functional fibrinogen £8.33 each; platelet function £70 each||Variable according to test (£0.29- £2.68 per test)|
|Cost of cup + pin||Plain cup £5.05, heparinase cup £10.15||Cup £3.09|
|Cost of running one ‘basic’ test||Kaolin vial + plain cup; total £7.57 (only one cup/channel is required for a ‘basic’ test)||Reagents £2.64 + 2 cups £6.19; total £8.83 (two cups/ channels are required for a ‘basic’ test). It should be noted that due to the multiuse vials the cost per test would increase if any reagent were wasted e.g. if expired|
|Aftercare costs||Yearly maintenance/wear/breakdown cover & service £2000/year (for 2-channel single unit; £1700 for each additional unit)|
If no aftercare contract: £300 callout + £120/h labour + parts
|Yearly maintenance/wear ∼£1081/year; increases to £1400/year with breakdown cover|
If no aftercare contract: annual service included for 2 years while under guarantee; variable thereafter
|If machine fails||On-site repair aimed for; replacement provided within 48 h or 72 h according to level of cover||On-site repair aimed for; replacement provided next working day|
|Training||Minimum 2 days on-site with 24-h on-call facility; as many follow-up training days as required in first 6 months; one day per month for next 6 months if required|
Tutorial book and sign-off exam
|Two days on-site + 1 refresher day for four operators; any further training £1500/day plus expenses|
|Summary and general opinion of assessors||Advantages: cheaper; well known and more widespread use in UK; therefore more extensive literature; good training programme and service support; screen easier to follow and appearance preferred; good technical support; can see other results while running test; Windows software; can look at effect of low molecular weight heparin|
Disadvantages: two channels per machine (though a ‘basic’ test requires only one channel); exporting results less flexible; manual pipetting possibly more prone to error (though automated available); more prone to vibration (though this was tested and the integral compensation software found to be effective)
|Advantages: integrated system; more resistant to vibration; automatic pipetting; easy step-by-step on-screen instructions; four channels per machine (though a ‘basic’ test requires two channels)|
Disadvantages: more expensive; less well known in UK; less attractive training programme; bulky appearance, detachable small parts which could be lost; more complicated tests requiring multiple reagents; complicated screen options; cannot see other results while running test; Linux software; cannot look at effect of low molecular weight heparin. Running costs may be increased for the occasional user; otherwise comparable
Readers will be familiar with the ‘head-to-head’ format that is popular with reviews of non-medical items such as computers, cars and household appliances, whilst medical reviews have tended to be of single items, focused on scientific principles, or based on statistical comparisons of performance. We felt a need for a more practical approach, which we feel represents more closely the process undertaken within anaesthetic departments. We accept that our assessments and conclusions are subjective, but the information/specifications on which they are based are as accurate as we can obtain, and the opinions/comments were remarkably consistent amongst the assessors. The overall conclusion was that the TEG® represented the best compromise between usability, usefulness and cost, currently – although even the lesser amount required represents a significant challenge for our department and the merits of having access to such a device , when compared with other financial priorities, is still the subject of some discussion.
We are grateful to the manufacturers, distributors and representatives for their help and support in facilitating this evaluation. KA has previously undertaken research involving the ROTEM® while undertaking a research fellowship funded by Smiths Medical Inc, Keane, NH, USA and did not participate in the evaluation.