©Zaiets Roman
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HAEMATOLOGY
Novel POCT transforms decision-making
The Royal Wolverhampton NHS Trust and Stago UK have collaborated in a joint interventional study to reduce blood transfusion costs while ensuring patient safety for those undergoing cardiac surgery.
The laboratory and cardiac teams at Wolverhampton’s New Cross Hospital are taking part in a pioneering point-of-care (POC) interventional study, using Stago UK’s Quantra system to improve transfusion decisions in cardiac surgery. The objectives are to improve patient safety, deliver appropriate treatment, and reduce the unnecessary use of expensive blood products. Jayne Parkes, principal clinical scientist for haematology, is leading the clinical governance aspects of the study and puts patient safety at the top of the laboratory’s agenda. She explained: “In preparation, the laboratory has already carried out a real-time verification study on the Quantra. This compared the core precision of critical parameters between laboratory and point of care in the interests of patient safety, and to help enable accreditation to ISO 15189. “The positive outcomes of the study have enabled the laboratory to demonstrate to clinical colleagues that there is a good correlation between point-of-care and accredited laboratory results. There is no point in risking patient safety by giving unnecessary blood products if we can provide
data that better informs medical decision- making when a critical bleed occurs.” In a separate study, UK NEQAS has already confirmed the core precision of the instrument, putting it firmly in line with laboratory accredited standards. The UK NEQAS report shows that the Quantra has consistently demonstrated robustness and good precision, with a 5% coefficient of variation (CV) for the QPlus Quality Control Level 2 cartridge, and an overall CV range of between 2.6% and 6.9%. The report further confirms that the results would be suitable benchmarks for a future external quality assessment (EQA) compliance programme. Based on the laboratory’s initial verification study findings, the cardiac teams at the 850-bed acute hospital, part of Royal Wolverhampton NHS Trust, has already started to use the Quantra for a further interventional evaluation.
Clinical algorithm for significant bleeding
The initial real-time comparative work to verify the results is the first step in a longer- term interventional study to compare the
effectiveness of the new point-of-care system. If the cardiac interventional study is successful, the teams will use the findings to create a new algorithm, which, said Ms Parkes, may “transform decision-making in the requesting of blood products in the event of significant clinical bleeding”. The laboratory’s initial comparative analysis assessed the blood of 10 patients at three critical time points: pre-surgery, the midpoint when on the bypass pump (after rewarming), and after surgery, when protamine had been administered. The Quantra analyser was actually based in the cardiac operating theatre so that a sample could be tested near the patient at these three time points.
Samples were fast-tracked to the hospital
laboratory for haematocrit (Hct), platelet count, prothrombin time-international normalised ratio (PT-INR), activated partial thromboplastin time (APTT) and fibrinogen analysis. For comparison, the Quantra measured clot time (CT), clot stiffness (CS), clot time with heparinase (CTH) and fibrinogen contribution to clot stiffness (FCS) with the Qplus cartridge. From these tests, two additional parameters were also calculated: clot time ratio (CTR) and platelet contribution to clot stiffness (PCS). Overall, the study pointed to a good correlation between Quantra QPlus parameters and the standard laboratory tests. Several interesting findings emerged, one especially around the decision whether or not to transfuse, and the dangers of over-transfusion.
Effect of haematocrit on accuracy
In Figure 1, plasma fibrinogen is shown to decrease with decreasing Hct, whereas in the Quantra analysis FCS is shown to increase with decreasing Hct. Other studies have already shown that lowering Hct increases fibrin clot stiffness.1,2
As a
Clinicians have to make very fast decisions about how to treat significant bleeding in patients at a time of acute perioperative situations.
NOVEMBER 2019
consequence, at low Hct the laboratory will report lower fibrinogen values than Quantra. However, Hct is generally lower when a patient is on bypass. Therefore, the
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