Point-of-care D-dimer testing in emergency departments

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1 Art & science venous thromboembolism Point-of-care D-dimer testing in emergency departments Udo Marquardt and Daniel Apau describe a literature review of the benefits, including shorter turnaround times and quicker diagnosis, of a technique to exclude venous thromboembolism Correspondence udomarq@gmail.com Udo Marquardt is an emergency nurse practitioner, at King s College Hospital NHS Foundation Trust, London Daniel Apau is a lecturer in advanced practice at City University, London Date of submission May Date of acceptance June Peer review This article has been subject to double-blind review and has been checked using antiplagiarism software Author guidelines journals.rcni.com/r/ en-author-guidelines Abstract Overcrowding and prolonged patient stays in emergency departments (EDs) affect patients experiences and outcomes, and increase healthcare costs. One way of addressing these problems is through using point-of-care blood tests, laboratory testing undertaken near patient locations with rapidly available results. D-dimer tests are used to exclude venous thromboembolism (VTE), a common presentation in EDs, in low-risk patients. However, data on the effects of point-of-care D-dimer testing in EDs and other urgent care settings are scarce. This article reports the results of a literature review that examined the benefits to patients of point-of-care D-dimer testing in terms of Introduction VENOUS THROMBOEMBOLISM (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), has an annual incidence of between one and two per,000 people (NHS England 203, Centers for Disease Control and Prevention 205) and is the third leading cause of vascular death in Western populations after myocardial infarction and stroke (Goldhaber 2007). Clinicians must, therefore, consider VTE in patients who present with leg complaints as well as those who present with chest pain or breathing difficulties (Goodacre et al 2005). Only 0% of patients referred for radiological investigations such as leg ultrasounds have confirmed DVT (Wells et al 2006), so the usual process in primary and emergency care is to calculate a pre-test probability (PTP) score for DVT or PE (Table, page 30, and Table 2, page 3). If the score is low a laboratory D-dimer test is undertaken, which is highly sensitive for VTE reduced turnaround times (time to results), and time to diagnosis, discharge or referral. It also considers the benefits to organisations in relation to reduced ED crowding and increased cost effectiveness. The review concludes that undertaking point-of-care D-dimer tests, combined with pre-test probability scores, can be a quick and safe way of ruling out VTE and improving patients experience. Keywords deep venous thrombosis, pulmonary embolism, venous thromboembolism, point-of-care D-dimer, turnaround times, emergency department, urgent care centre (National Institute for Health and Care Excellence (NICE) 202). D-dimer is a small protein fragment present in the blood after a blood clot has been degraded by fibrinolysis, and measurement of D-dimer levels is made possible by the presence of monoclonal antibodies that bind to D-dimer fragments (Righini et al 2008). A positive result indicates thrombosis; however, there are other causes of raised D-dimer, including liver disease, inflammation, malignancy, pregnancy or surgery (Righini et al 2008). Patients with high PTP scores should have an ultrasound leg vein compression scan, to investigate for DVT, or a computerised tomographic pulmonary angiogram (CTPA), for a suspected PE (Wells et al 2003, 2006, NICE 202). A DVT can be safely ruled out if the PTP score is low and the D-dimer result is negative, and patients should then be assessed for an alternative diagnosis. A high D-dimer test result means VTE is more likely and further investigations are indicated. EMERGENCY NURSE September 205 Volume 23 Number 5 29

2 Art & science acute xxxxxxx venous care thromboembolism Table Two-level deep vein thrombosis Wells score Clinical feature Points Patient score Active cancer (treatment ongoing, within six months, or palliative) Paralysis, paresis or recent plaster immobilisation of the lower extremities Recently bedridden for three days or more, or major surgery within 2 weeks requiring general or regional anaesthesia Localised tenderness along the distribution of the deep venous system Entire leg swollen Calf swelling at least 3cm larger than asymptomatic side Pitting oedema confined to the symptomatic leg Collateral superficial veins (non-varicose) Previously documented deep vein thrombosis (DVT) An alternative diagnosis is at least 2 as likely as DVT Clinical probability simplified score DVT likely 2 points or more DVT unlikely point or less (NICE 202, adapted from Wells et al 2000, 2003) One of the problems for patients who require D-dimer tests in emergency departments (EDs) is that waiting for results, referred to as turnaround time, can be lengthy, which can also slow down overall patient flow. However, point-of-care PTP and D-dimer tests can be performed in these departments and results are usually available within ten to 20 minutes. As D-dimer testing is mainly used to exclude VTE, negative tests combined with low PTP scores, called the negative predictive value (Geersing et al 2009), undertaken in GP practices could also reduce ED overcrowding by avoiding unnecessary ED referrals and investigations. Point-of-care D-dimer blood tests produce results more quickly than laboratory testing and are gradually being introduced into EDs and larger GP practices. There are two main types of test: quantitative and qualitative. Quantitative tests require analysers, which provide precise and accurate results in numbers and cut-off values, and which vary in size, price and maintenance needs. Qualitative tests involve placing fingerpick or venous blood from a capillary pipette into the sample well of a flat single-use test device. The presence of a line indicates a raised D-dimer, while no line indicates a negative test. Results can be read after ten minutes at the test zone. The advantages of the qualitative test are that the devices used are simple to use and require little equipment; however, they are less accurate than quantitative tests. The accuracy of point-of-care D-dimer tests has been examined in numerous studies and meta-analyses (Wells et al 2006, Di Nisio et al 2007, Geersing et al 2009, 200); however, the effects on patient flow, turnaround times and costs have not been thoroughly evaluated. Therefore, a literature review was undertaken to determine if point-of-care D-dimer testing could be beneficial to patients with suspected VTE in urgent care or ED settings in terms of reduced turnaround time, and time to diagnosis, discharge or referral. Literature review A systematic search of Embase, Medline, Cochrane, EBM and NHS Economic Evaluation Database for literature was undertaken based on a number of search terms and, following retrieval, screening and exclusion, nine articles were used for critical analysis. A summary of the search process is given in Box, page 32. Grey literature and manufacturers product literature were briefly assessed on websites including the Grey Literature Report and through Google, and NICE (202) guidelines on VTE were consulted. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) checklist (Moher et al 2009) was used to report the systematic review. The methodological quality of the selected studies in terms of rigour, credibility and relevance was screened using the Critical Appraisal Skills Programme (204) tool for diagnostic tests, cost effectiveness and economic evaluation. Different outcomes and outcome measures were used in the retrieved studies. For example, some measured time from triage, others from time seen by a doctor to result time and discharge time. Therefore, they were analysed using a narrative comparison and results synthesis. Ethical approval was addressed appropriately in all studies. Results Seven studies were related to turnaround time and two to cost effectiveness, but none used complete blinding of all clinicians, which makes reliability and generalisability questionable, and the mix of prospective and retrospective studies makes direct comparison difficult. 30 September 205 Volume 23 Number 5 EMERGENCY NURSE

3 Table 2 Two-level pulmonary embolism Wells score Clinical feature Points Patient score Clinical signs and symptoms of deep vein thrombosis (DVT) (minimum of 3 leg swelling and pain with palpation of the deep veins) An alternative diagnosis is less likely than pulmonary embolism (PE) 3 Heart rate more than 00 beats per minute.5 Immobilisation for more than three days, or surgery in the.5 previous four weeks Previous DVT or PE.5 Haemoptysis Malignancy (having treatment, treated in the last six months, or palliative) Clinical probability simplified scores PE likely More than 4 points PE unlikely 4 points or less (NICE 202, adapted from Wells et al 2000, 2003) The turnaround time studies involved a total of 3,279 patients and the eleven point-of-care D-dimer test kits are listed in Box 2, page 33. All the tests can give a diagnostic result within five to 20 minutes. The rest of this section critically analyses the nine retrieved articles. Antovic et al (202), in a prospective study that compared five point-of-care D-dimer kits with standard laboratory methods, found that the Stratus and Vidas tests have excellent sensitivities, but need large analysers and a centrifuge so might be more suitable for EDs with mini-laboratories and trained staff. The researchers found that the Pathfast and Cardiac tests, with the aid of a portable hand-held analyser, were suitable for use in urgent and primary care settings, but that the NycoCard was unsuitable as it produced eight false negatives compared to the standard reference. Another prospective cohort study measured how the use of a satellite laboratory, which used the NycoCard II, affected patient turnaround and clinical decision-making times in,065 patients divided into control and intervention groups (Leman et al 2004). The study included various biomarkers of which D-dimer was one. After installation of the ED satellite laboratory, data were collected from various stages of patients journeys, including at arrival, clinical decision, diagnosis and discharge times. Multiple regression modelling determined whether any particular measured confounders affected decision times. Results showed a large decrease in processing times for samples handled in the laboratory, discharge times improved by 3.8 minutes (P=0.009) for the D-dimer group, and the turnaround test time was 66. minutes faster than the control group (95% confidence interval (CI) 4.8 to 90.4). Information on clinical effects was also collected by entering treatments such as IV therapy and medication into the data collection form, and showed that twice as many patients in the intervention group had their treatment modified after the blood results. The researchers also found a long interval between the results being available on the computer and clinicians being aware of them (mean minutes), and there was an additional cost of 2 per patient (cost of each test). Mean time spent waiting to be seen by a doctor improved in both groups: 6.5 minutes in the intervention group and 27.4 minutes in the control group, which suggests there was some bias or the Hawthorne effect (Parahoo 997). However, it was difficult to conduct a blinded study. A prospective single-centre diagnostic study of 00 patients (Sen et al 204) compared the Alere Triage test to laboratory D-dimer tests in patients with signs and symptoms of VTE. Although the main aim was to compare the accuracy of laboratory D-dimer and point-of-contact tests, the secondary outcomes included turnaround times and whether these influenced patients length of stay in the ED. All patients suspected of having a VTE were stratified using PTP scores (NICE 202). The mean turnaround time for point-of-contact tests was 5 minutes (range 7-3 minutes) compared to 90 minutes for the laboratory turnaround times (range minutes), but it is unclear if patients length of stay improved. The incidence of patients who presented with possible VTE was only.6% of the total attendance, and most (7%) had low PTP scores. Patients with low PTP scores can benefit most from D-dimer tests, as a low score combined EMERGENCY NURSE September 205 Volume 23 Number 5 3

4 Art & science acute venous care thromboembolism Box Summary of search process with a negative test can rule out VTE (Wells et al 2000, 2003, NICE 202). Perveen et al (203) undertook a prospective observational study to compare the AQT90 FLEX D-dimer analyser with laboratory test times from triage to result. As a secondary objective, the sensitivities of the two tests were compared. The PTP criteria were applied by senior medical staff and excluded high-risk patients so that 04 patients were included in the study and all The following databases were used: Embase from Cochrane Central Register of Controlled Trials (CENTRAL) Cochrane Database of Systematic Reviews Cochrane Methodology Register Evidence-Based Medicine (EBM) reviews of abstracts of reviews EBM reviews NHS economic evaluation database 205 Ovid Medline Ovid Nursing Full text Plus Three searches were undertaken and results from the third search were used for the literature review. This was based on combinations of the following search terms:. D-dimer and point of care 2. Pulmonary embolism 3. Deep vein thrombosis 4. Venous thromboembolis Medical Subject Headings (MeSH) and Thesaurus terms expanded by database (Ovid Sp platform). care 2. d-dimer 3. deep 4. deep vein thrombosis 5. embolism 6. of 7. point 8. point of care 9. pulmonary 0. pulmonary embolism. thromboembolism 2. thrombosis 3. vein 4. venous 5. venous thromboembolism The third search returned 505 texts, from which 30 remained following review of the abstracts. Another 4 were excluded as they did not focus on turnaround times or were not primary studies. The remaining texts had to focus on point-of-care D-dimer and at least one of the following criteria: turnaround time, quality of care, cost effectiveness, user friendliness, length of stay, time to diagnosis, time to result. This resulted in 6 texts, of which four were duplicates and three did not focus on D-dimer. The final total was therefore nine. had both tests. Median time for obtaining D-dimer results was 258 minutes for the laboratory tests (interquartile range minutes), and 46 minutes for point-of-care tests (interquartile range minutes). The median difference was 0.5 minutes (interquartile range minutes). Time to result for the point-of-contact test was significantly lower (04 minutes, 95% CI minutes, P value <0.000). Although this might seem long, the length of time was measured from triage as blood tests were taken early in the patient journey. Geersing et al (200) investigated the accuracy and user friendliness of five point-of-care tests: Cardiac, Pathfast, Triage, Vidas, which are quantitative, and Clearview Simplify, which is qualitative. In this large prospective study, 577 patients in primary care with signs and symptoms of DVT had venous blood taken for the quantitative tests and capillary blood for the qualitative test. Technicians were blinded to the results of other D-dimer tests and the compression ultrasounds that followed the blood tests. All point-of-care tests had negative predictive values of more than 98%, with sensitivity ranging from 9% for Clearview Simplify to 99% for Vidas, and time to results varied from 0 minutes (Clearview Simplify) to 38 minutes (Vidas). User-friendliness analysis indicated that ease of operation and risk of errors were comparable. However, since Clearview Simplify does not require an analyser or calibration, and gives results within ten minutes, it could be the preferred option in primary care. It does, however, require reading of a control and second line similar to a pregnancy test, which could result in the inter-observer discrepancies described by some of the clinician participants. Calibration for the Pathfast and Vidas tests might require some laboratory skills so Cardiac and Triage might be better options for an ED. Prices for one disposable kit were between 5 and 0 (between 3.54 and 7.08), and between 5,000 and 5,000 for the analyser required for the quantitative tests. However, some analysers can test up to 84 other biomarkers (Cardiac), including electrolytes, troponin and full blood count, so could be useful in EDs as satellite laboratories. A retrospective and multi-centre analysis study (Leong et al 204) evaluated a change in infrastructure and point-of-care testing in 7 EDs in Shanghai. Only 25 point-of-care D-dimer tests were undertaken, compared to 348 laboratory tests, and they were only 0 minutes faster than laboratory results (52 minutes and 62 minutes respectively). 32 September 205 Volume 23 Number 5 EMERGENCY NURSE

5 The authors report that the relative delay in turnaround times was because point-of-care test machines were placed in the laboratories instead of EDs, which defeated the object. The study is limited because of the low impact, small number of tests and because the devices are not used in Europe. Lee-Lewandrowski et al (2009) evaluated the use of a point-of-care D-dimer test (Biosite Triage) in a US ED satellite laboratory, by comparing turnaround times for 462 patients before and after implementation (252 before, 2 after). The turnaround time reduced from 20 minutes to 25 minutes (79% change), the mean ED length of stay decreased from 8.46 to 7.4 hours (P=0.6, unpaired t-test) and the median ED length of stay dropped from 6.20 to 5.88 hours (P=0.26, Mann-Whitney U test). Additionally, hospital admissions decreased by 3.8%, ED discharges increased by 7.3%, and the number of patients admitted for short-stay observations in the ED increased by 6.4%. The number of D-dimer tests also increased by 2.3%. Prevalence of VTE post-test was only 2.4%, but the authors explained that the test had to be requested by an ED physician so the sample represented a more typical population and reflected real practice. Other studies report between 7% and 36% prevalence (Brown et al 2002, Stein et al 2004), which raises the issue of appropriate use of the test. Overuse and misinterpretation could increase healthcare costs and patient inconvenience and risk through, for example, unnecessary ultrasounds, computed tomography scans, treatment with low-molecular-weight heparin with associated risks of bleeding, and time wasted waiting for more tests and treatment. Of note was the relatively long ED stays compared to the UK, but the change in length of stay is significant. Two studies (Ten Cate-Hoek et al 2009, Hendrikson et al 205) assessed the incremental cost effectiveness of a clinical decision rule combined with a point-of-care test in primary care. Both were based on the results of a large study involving,028 patients (Bueller et al 2009), which evaluated an adjusted clinical decision rule for primary care combined with the Clearview Simplify test. Bueller et al (2009) assessed the test as safe when combined with the rule, and it only failed to detect.4% of DVTs. Cost effectiveness was not evaluated in the initial study, so Ten Cate-Hoek et al (2009) aimed to do this by constructing an artificial health state model that measured and then compared the model described above with diagnostic emergency care strategies. There were average cost savings of 99 (95% CI saved) with the Box 2 Point-of-care D-dimer test kits used in the retrieved studies Alere Triage (Alere Ltd, UK) AQT90 FLEX (Radiometer) Biosite Triage (Alere Ltd, UK) Cardiac (Roche Diagnostics) NycoCard (Nyomed Pharma, Norway) NycoCard Reader II Pathfast (Mitsubishi Chemical, Japan) Stratus (Siemens Diagnostics, Germany) Triage (Biosite) Vidas (Biomerieux, France) Clearview Simplify (Inverness Medical) (qualitative test) Clearview Simplify test, with a quality-adjusted life years (QALY) loss of 0.002, which equates to less than a day. Hendrikson et al (205) updated and extended the model to assess other point-of-care tests, and conducted a systematic search to identify those in use at that time and studies that had evaluated their accuracy. Only tests that can be easily applied in primary care, such as hand-held portable systems with ease of performance and appropriate analysing speed, were considered. More than 5,000 patients were included in the study and the diagnostic accuracy of the tests was used as a base to calculate health outcomes, expressed in QALY over ten years. Clearview Simplify was more cost effective than Cardiac, NycoCard or Triage. There was a minimal QALY loss of 9 hours due to the slightly lower sensitivity of point-of-care tests compared to the control laboratory tests. Models were both based on the Dutch healthcare system and underlying cost structures, which reduces applicability to the UK. Descriptions of the studies retrieved in the authors literature review can be seen in Table 3, which is available at journals.rcni.com/r/ literaturereviewfindings Discussion The methodological quality of the studies reviewed was moderate; most were well designed, but were not randomised or blinded. The number of point-of-care D-dimer tests examined or compared in each study was small, and some studies used accuracy as a primary outcome measure. The results seem reliable and repeatable with internal validity, but might be different if applied to larger populations, which reduces external validity. All studies showed a reduction in turnaround time that was reflected in reduced lengths of stay and clinical decision-making times. EMERGENCY NURSE September 205 Volume 23 Number 5 33

6 Art & science The acute venous synthesis care thromboembolism of art and science lived by the nurse in the nursing act JOSEPHINE G PATERSON The review suggests that it is important to select a point-of-care test that is appropriate to the setting. For example, Lee-Lewandwroski et al (2009) advise that only some point-of-care tests were beneficial in EDs and making the wrong choice could prolong ED turnaround times. They also argue that determining the cost-to-benefit ratio is challenging because of the confounding variables, such as ED length of stay, changes in workflow and effect on revenues. The cost of overcrowding in EDs, in terms of patient safety and cost of care, is considerable (Richardson 2006, Forero and Hillman 2008, Pines and Hollander 2008, Guttmann et al 20). Therefore, resources such as point-of-care tests should be considered as a way of increasing patient throughput. Higginson (202) claim that better hospital laboratory systems could offer faster turnaround times and subsequently improve ED throughput, while Leman et al (2004) point out that hospital laboratory staff can work faster when they know point-of-care evaluation is taking place. There is much research on the accuracy of point-of-care D-dimer tests, but a lack of evaluation of costs and turnaround times. Therefore, ongoing audit would be a useful way of evaluating the benefits for patients in terms of quicker outcomes, accuracy and cost effectiveness. It is likely that costs of the test kits will decrease as more are used. However, almost all of the quantitative tests require some form of analyser, which needs to be maintained and checked for quality. In busy EDs, experienced departmental technicians, who already work as advanced phlebotomists, could also undertake safety checks and calibrate blood-gas machines. Hendrikson et al (205) suggest that pathology laboratory staff and other stakeholders, such as clinical chemists, should be consulted about which tests to use and how to integrate these resources fully into hospitals to ensure best value for money and safety. Quantitative tests are more accurate, so are probably more useful in EDs, which are traditionally risk averse, and some manufacturers provide analysers that can be used for a range of biomarkers, so could be used for a range of tests that are commonly undertaken in EDs. Some studies show that faster result turnaround times are not translated into improved patient turnaround times. This could be because clinicians see several patients simultaneously and might not have caught up with results, or because they do not fully trust the point-of-care results and are waiting for laboratory confirmation. In fact, in some studies clinical decisions could not be made until laboratory results had been seen (Perveen et al 203). It would be interesting to research the barriers to implementation of point-of-care D-dimer tests in primary, urgent and emergency care, as they are not widely used despite having been available for a decade. A randomised control trial on the effects of point-of-care blood tests on ED processing times References Antovic J, Hooeg K, Forslund G et al (202) Comparison of five point-of-care D-dimer assays with the standard method. International Journal of Laboratory Haematology. 34, Asha S, Chan A, Walter E et al (204) Impact from point-of-care devices on emergency department patient processing times compared with central laboratory testing and blood samples: a randomized controlled trial and cost-effectiveness analysis. Emergency Medical Journal. 3, Brown M, Rowe B, Reeves M et al (2002) The accuracy of the enzyme linked immunosorbent assay D-dimer test in the diagnosis of pulmonary embolism. Annals of Emergency Medicine. 40, Bueller H, Ten Cate-Hoek A, Hoes A et al (2009) Safely ruling out deep venous thrombosis in primary care. Annals of Internal Medicine. 50, Critical Appraisal Skills Programme (204) CASP Checklists. tinyurl.com/psk3o2m (Last accessed: July ) Centers for Disease Control and Prevention (205) Deep Vein Thrombosis/Pulmonary Embolism. tinyurl.com/7cn2p8 (Last accessed: July ) Department of Health (20) Correspondence Performance Management of NHS A&E Services Using the Clinical Quality Indicators. tinyurl. com/q5gxbrc (Last accessed: July ) Di Nisio M, Squizzato A, Rutjes A et al (2007) Diagnostic accuracy of D-dimer test for exclusion of venous thromboembolism: a systematic review. Journal of Thrombosis and Haemostasis. 5, Forero R, Hillman K (2008) Access block and overcrowding: a literature review. Australasian College of Emergency Medicine. tinyurl.com/ o29g2ko (Last accessed: July ) Geersing G, Janssen K, Oudega R et al (2009) Excluding venous thromboembolism using point-of-care D-dimer tests in outpatients: a diagnostic meta-analysis. British Medical Journal. 339, b2, 990. Geersing G, Toll D, Janssen K et al (200) Diagnostic accuracy and user friendliness of five point-of-care D-dimer tests for the exclusion of deep vein thrombosis. Clinical Chemistry. 56,, Goldhaber S (2007) Preventing pulmonary embolism and deep vein thrombosis: a call to action for vascular medicine specialists. Journal of Thrombosis and Haemostasis. 5, 5, Goodacre S, Sutton A, Sampson F (2005) Metaanalysis: the value of clinical assessment in the diagnosis of deep venous thrombosis. Annals of Internal Medicine. 43, Guttmann A, Schull M, Vermeulen M et al (20) Association between waiting times and short-term mortality and hospital admission after departure from emergency department: population based cohort study from Ontario. Canada. British Medical Journal. 342, d2, 983. Hendrikson J, Geersing G, van Voorthuizen SC et al (205) The cost effectiveness of point-ofcare D-dimer tests compared with a laboratory test to rule out deep venous thrombosis in primary care. Expert Review of Molecular Diagnostics. 5,, Higginson I (202) Emergency department crowding. Emergency Medical Journal. 29, Lee-Lewandrowski E, Nichols J, Van Cott E (2009) Implementation of a rapid whole blood D-dimer test in the emergency department of an urban academic medical centre. American Journal of Clinical Pathology. 32, September 205 Volume 23 Number 5 EMERGENCY NURSE

7 (Asha et al 204) found that junior clinicians were unable to make decisions and required senior guidance, and the greatest effects were observed when senior clinicians decided which tests should be ordered. The authors suggest that a structured clinical pathway for point-of-care testing would realise the benefits. Qualitative tests such as Clearview Simplify seem more suited to primary or urgent care as they work well in low-risk populations, do not require calibration or analysers, and are easy to use, although 25% of participants in one study (Geersing et al 200) said interpreting the colour was more difficult compared to quantitative tests. Ten Cate-Hoek et al (2009) and Hendrikson et al (205) both demonstrate significant cost savings by ruling out VTE in primary or urgent care centres and thereby avoiding the need to send patients to EDs. This could improve patient journeys, reduce waiting times and the costs associated with ED attendances and ultrasounds, and perhaps contribute to reducing crowding. Quality indicators (Department of Health 20) for EDs include admission rates for DVT and cellulitis, service experience, time to initial assessment and treatment; quicker diagnostic results could help meet these targets. Limitations The diversity of the retrieved studies makes it difficult to draw firm conclusions or make direct comparisons as they use different cut offs and outcome measures, and were conducted in various countries with radically different healthcare systems. None of the studies were randomised, which some authors said was difficult to arrange. However, Asha et al (204) managed to conduct a randomised control trial of point-of-care tests, although they were not for D-dimer and the trial was not blinded since it is difficult to hide pointof-care testing. In the future, however, when pointof-care testing is more established it should be easier to collect unbiased data. Finally, there may be publication bias since no unpublished studies were included in the review despite attempts to identify them. Conclusion Findings from the literature review suggest that point-of-care D-dimer tests can safely improve patient journey times. Clinicians and managers should consider the evidence, but conduct a thorough assessment of individual tests, including turnaround times, cost, accuracy and ease of use. Some tests, such as Clearview Simplify, require no analyser, but most of the others do and their costs vary significantly, as does the need for maintenance, quality control and calibration. Plans to implement such tests should be discussed with local laboratory management teams, who can advise and support ongoing safety and quality control. Finally, longitudinal research designed to capture outcomes and to ensure safety and cost effectiveness should be undertaken. Online archive For related information, visit our online archive and search using the keywords Conflict of interest None declared Leman P, Guthrie D, Simpson R et al (2004) Improving access to diagnostics: an evaluation of a satellite laboratory service in the emergency department. Emergency Medical Journal. 2, Leong W, Chen L, Yu P et al (204) The clinical situation of point-of-care testing and its future development at the emergency department in Shanghai. Journal of Laboratory Automation. 9, 6, Moher D, Liberati A, Tezlaff J et al (2009) Preferred Reporting Items for Systematic Reviews and Meta-analyses: The PRISMA Statement. tinyurl.com/nlzloqs (Last accessed: July ) National Institute for Health and Care Excellence (202) Venous Thromboembolic Disease: The Management of Venous Thromboembolic Diseases and the Role of Thrombophilia Testing. tinyurl.com/nma2qc2 (Last accessed: July ) NHS England (203) Commissioning Services that Deliver High Quality VTE Prevention: Guidance for Commissioners. tinyurl.com/ qymphv7 (Last accessed: July ) Parahoo K (997) Nursing Research. Second edition. Palgrave Macmillan, New York NY. Perveen S, Unwin D, Shetty A et al (203) Point-of-care D-dimer testing in the emergency department: a bioequivalence study. Annals of laboratory Medicine. 33, Pines J, Hollander J (2008) Emergency department crowding is associated with poor care for patients with severe pain. Annals of Emergency Medicine. 5, -5. Richardson D (2006) Increase in patient mortality at 0 days associated with emergency department overcrowding. Medical Journal Australia. 84, Righini M, De Moerloose P, Bounmeaux H et al (2008) D-dimer for venous thromboembolism diagnosis: 20 years later. Journal of Thrombosis and Haemostasis. 6, Sen B, Kesteven P, Avery P (204) Comparison of D-dimer point-of-care test against current laboratory test in patients with suspected thromboembolism presenting to the emergency department. Clinical Pathology. 67, Stein P, Hull R, Patel K et al (2004) D-dimer for the exclusion of acute venous thrombosis and pulmonary embolism. Internal Medicine. 40, Ten Cate-Hoek A, Toll D, Bueller H et al (2009) Cost effectiveness of ruling out deep venous thrombosis in primary care versus care as usual. Journal of Thrombosis and Haemostasis. 7, Wells P, Anderson D, Rodger M et al (2000) Derivation of a simple clinical model to categorize patients probability of pulmonary embolism: increasing the model s utility with the SimpliRED D-dimer. Thrombosis and Haemostasis. 83, Wells P, Anderson D, Rodger M et al (2003) Evaluation of D-dimer in the diagnosis of suspected deep vein thrombosis. New England Journal of Medicine. 349, 3, Wells P, Owen C, Doucette S et al (2006) Does this patient have deep vein thrombosis? Journal of American Medical Association. 295, 2, EMERGENCY NURSE September 205 Volume 23 Number 5 35