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Chest pain at the emergency department: point-of-care testing

Ulf Martin Schilling
31 July, 2012  
Ulf Martin Schilling MD PhD
Department of Medicine and
Health Science,
Linköping University and Department of Accidents and Emergencies,
Linköping University Hospital, Sweden
 
Point-of-care testing (POCT) is defined as any testing at, or close to, the patient’s bed. The wider definition encompasses a thorough physical examination, physiological and radiological investigation and laboratory analysis. Most often the focus is on laboratory testing when discussing POCT (closer definition), and the other modalities are omitted. In this article, POCT is accepted as in the wider definition and the  rationale behind POCT, time management aspects of POCT and economics are discussed. 
 
Chest pain is a common symptom among patients attending the emergency department (ED). Approximately 1 in 20 patients attending the ED will present with acute chest pain requiring further diagnostic workup.(1) From the emergency physician’s point of view, the underlying causes for chest pain can be designated as immediately life threatening, potentially life threatening, or other.
 
Diagnosing patients presenting with chest pain
To differentiate rapidly among the different causes of chest pain, the physician frequently relies on the clinical picture, the patient’s clinical history, POCT and the response to therapy. Even then it is not possible to obtain a final diagnosis in all cases until further testing is performed, which most commonly requires admission to the hospital. 
 
As taught in emergency medicine courses, physicians should rule out immediately life threatening pathology within minutes, and even potentially life threatening pathology within a minimal period of time before focusing on other potential diagnosis. The majority of patients with chest pain will not suffer life-threatening disease requiring further investigation or admission to the hospital, and most of these patients will be found early in the diagnostic process by anamnesis, the clinical picture and assessment of the patient’s relative risk of disease without any further investigation. However, as there will always be a patient presenting with atypical symptoms of severe illness, there will be a margin of uncertainty, even for the most experienced doctors. The use of further investigations complementing the clinical assessment is often warranted. 
 
Because of a multitude of potential diagnoses presenting with chest pain, it might be assumed that a multitude of investigations would be necessary to differentiate among the potential causes. However, experienced physicians are able to rule out the majority of the potential pathology with a limited number of investigations and often do not have to perform any investigation at all besides a clinical investigation of their patients. 
 
Rationale behind POCT in the ED
Time is often limited in the ED. A common strategy is the observation of patients if the diagnosis cannot be established at the first place, or who suffer increased risk that chest pain is caused by life-threatening disease as myocardial infarction. These patients will be admitted for active observation and often serial testing for myocardial damage. An increasing number of hospitals create observation units that often are run or managed by the ED.(2) 
 
The work at the ED usually requires diagnosis and therapy of several patients simultaneously, and both ED resources and hospital bed capacity are limited.  Furthermore, overcrowding is a common problem at many EDs, leading to a virtually unlimited demand of ED care. 
 
Time to diagnosis allowing further management of the actual patient is precious, because ED capacity is focused on potentially threatened patients as long as life-threatening disease has not been ruled out. The term of early goal-directed therapy has been established in sepsis, stroke and acute heart failure syndromes. In essence, early goal-directed therapy addresses acute organ dysfunction to adequately stabilise the patient by supportive means and – as importantly – by treating the underlying cause of organ malfunction and shock in critically ill patients.
 
Under these circumstances of critically ill patients in an abundance of patients, and a chronic shortage of time and working space, rapid and reliable investigation is a valuable tool to improve optimal flow at the ED as well as the management of the admitted patient. Here POCT plays a major role. 
 
POCT in chest pain
One of the most widely spread uses of POCT is the exclusion of chest pain of cardiac origin. According to the universal definition of myocardial infarction, myocardial infarction requires the evidence of myocardial necrosis in a clinical setting consistent with myocardial ischemia. Essentially, this is found by the detection of the rise (or fall) of cardiac biomarkers (preferably troponin) with signs of ischemia or during procedure; by sudden cardiac death or by pathological findings of acute myocardial infarction. Other reasons for the elevation of myocardial biomarkers are excluded from the definition of myocardial infarction.(3)  
 
Assessment of biomarkers is commonly used to differentiate between chest pain owing to cardiac ischaemia and other causes of chest pain. A multitude of biomarkers to facilitate early diagnosis of cardiac ischaemia have been tested and more are under current development.
 
Historically, lactate dehydrogenase, creatine kinase (CK), CK-MB and myoglobin were used as cardiac markers to be successively replaced by different troponins (which must be considered as today’s standard). However, troponins need to be supplemented by other test such as CKMB in cases of doubt or if suspecting early reinfarction. Because of this, panel testing is still widespread even though the majority of centres have adopted strategies based on the measurement of troponins. The POCT analysis of biomarkers can be completed by bedside imaging at the ED, for example by echocardiography, which allows the assessment of non-ischemic causes of chest pain as well as early (or late) detection of abnormal cardiac wall motility suggestive of myocardial infarction.(4) 
 
In a recent study with more than 2000 patients, panel testing of CKMB, troponin and B-type natriuretic peptide was not superior to troponin testing alone(5); however, patients undergoing POCT were more likely to be discharged directly from the ED, and if they were admitted, they were more likely to be admitted to coronary care. In a 30-day survey, patients undergoing POCT tended to rate their care slightly better than patients receiving laboratory testing. 
 
Economic analysis of POCT in chest pain
On economic analysis of the RATPAC trial, POCT was more expensive than laboratory analysis due to increased testing costs (£38.13) and staffing needed for analysis (£11.55). Due to secondary costs (treatment, coronary care, etc), patients tested by POC cost an additional £179.26 compared to patients tested by laboratory analysis in this study.(5) However, one of six centres participating in the study did reduce costs by 21.46% (£214.4) per POCT patient, whereas five out of six centers increased costs, by between 9.8% and 91.1% per patient (£104.2 to £646.57), with a mean total increase for all six centres of 20.54%  (£207.24). 
 
In a study conducted at the ED of University Hospital Linköping, using a POCT system significantly reduced the time to obtaining laboratory results by 48.5 (±28.67) minutes. A total of 41 clinically stable patients aged 18+ presenting to the ED owing to shortness of breath or chest pain were enrolled in the study. In all patients, the following tests were performed on venous blood: iSTAT Chem8+, cTNI and CG4+. Similar tests were performed in paralled at the central laboratory of the hospital. The TNI analysis was tested but omitted because of the use of hsTNI by the central laboratory instead. All samplings and analyses were performed by the same nurse and all samples for each patient were taken to central and local analyses at the same time. Central laboratory results and POCT correlated highly without clinically significant differences. In the local setting, the same study could show a potential of major savings by the use of POCT both on direct costs (the POCT in our setting was actually cheaper than central laboratory analysis) as indirect costs (if the time saved by POTC could be used to adapt staffing).(6,7) 
 
Assuming a baseline 40,000 patients annually with a mean 3.5 hours stay at the ED, we calculated that staffing for each single patient cost 1.5 US$/minute. Using Abbott’s iSTAT cartridges CG4+, Chem 8+ and troponin I analysis, we revealed a potential savings per patient of 111US$/patient on analysis costs, and further potential savings on staffing of 72.75US$ compared to central laboratory analysis. In total, 32,333 hours could be saved per year (2.910.000 US$) beside a 4.440.000 US$ reduction on laboratory costs – adding to a total of 7.350.000 US$ in potential savings. 
 
Time aspects
In our study, POCT results were available 48.5 minutes before central laboratory results were available. Under optimal circumstances, patients could be managed 48.5 minutes faster than by the current standard, potentially resulting in higher turnover rate at the ED, reduced waiting time, increased patient satisfaction and reduced overcrowding. However, the results of the validation trial could not be used in the clinical management of the patients. Whether these potential time-savings will translate into clinical practice remains to be seen.
 
In the multicentre DISPO-ACS-trial,(8) POTC was compared in the clinical setting towards central laboratory analysis regarding time to disposition at the ED. In four EDs 2000 patients with chest pain were included for serial POC testing or serial central laboratory testing. Early serial testing during a total of 360 minutes was performed on all patients in the study. Even if only 3% of central laboratory results were available within 30 minutes compared with 87.3% of POCT samples, no significant impact on processing time for the patients was observed; disposition times were varied and were reduced, unchanged or increased in different centres. A mean of 8 minutes per patient were saved for the whole study population by using POCT – with a mean time at the ED of 276 minutes for patients discharged, and 330 minutes for admitted patients. Interestingly, in the study it could be observed that in one of the four centres disposition time was reduced, and in one of four centres it was increased.(8) 
 
Why is POCT not used more widely?
In the wider definition every ED and GP is using POCT: ECGs, urinary dipsticks, glucose tests and C-reactive protein, and exhaled alcohol are effectively POCTs. However, not all EDs rely on POCT for the majority of their analyses. There are a number of reasons for this.
 
The impact of POCT on patient disposition is variable between different EDs even in the same setting, as shown by the DISPO-ACS trial.(8) The impact of POCT on the respective ED is therefore difficult to predict, and structural difficulties might influence whether the full potential of POCT can be achieved both in admitted patients and discharged patients, which was demonstrated in the same study. In the US-setting, legislation requires laboratory results to be available for emergency patients within 30 minutes, which could eliminate the need for POCT. Still, EDs in the US are among the major consumers of POCT as the legal time limit often is exceeded, which warrants the use of POCT instead. 
 
Legal demands on ED disposition time put increasing pressures on ED administration, and all technologies that can improve patient disposition time are welcomed if they are available at a reasonable cost. However, obtaining laboratory results is not always the limiting factor in ED disposition time, so the impact of POCT will be reduced if the burden of overcrowding exceeds human resources, or if in-hospital obstacles to admission or radiology capacity obstruct patient flow instead.
 
Furthermore, the cost of POCT inevitably varies in different settings(5,7) and might not be warranted locally. If POCT has no impact on patient care and disposition in the local setting, increased costs for POC will not be warranted.
 
The quality of POCT has been tested in different studies with varying results,(6,9,10) and before POCT is adopted it might be wise to revise the documentation and to test the analysis in the local setting.
 
One problem is the practical aspect of total patient flow. Not all processes are owned or influenced by the ED, so that the possibility of the ED adopting alternative technologies might be limited. In our setting, we tested the iSTAT cTNI analysis. As our cardiology department propagates the use of hsTNT instead, the practical use of POC cTNI is limited due to technical limitations (unfortunately, the tests cannot be compared directly, so that a patient’s disposition relies on the result of the central laboratory analysis).
 
Conclusions
Chest pain is a common symptom caused by multiple pathologies. Life-threatening pathology has to be ruled out as early as possible, and early goal-directed therapy should be adopted in critically ill patients. A number of bedside investigations and laboratory POCT options are available to the physician. In the clinical workup of the patient, POCT can be helpful in rapid differential diagnosis. Disposition time and costs per patient can be influenced by POCT but are subjected to local circumstances. The usefulness and clinical impact of POCT for each single ED has to be determined according to the actual setting.
 
References
  1. Goodacre S et al. The health care burden of acute chest pain. Heart 2005;91:229–30.
  2. Venkatesh AK et al. Use of observation care in US Emergency Departments, 2001 to 2008. PLoS ONE 6(9): e24326.doi:10.1371/journal.pone.0024326.
  3. Thygesen K et al; Joint EsC/ACCF/AHA/WHF Task Force for the Redefinition of Myocardial Infarction. Universal definition of myocardial infarction. J Am Coll Cardiol 2007;50:2173–95. 
  4. Ekelund U, Forberg JL. New methods for improved evaluation of patients with suspected acute coronary syndrome in the emergency department. Emerg Med J 2007;24:811-814. doi: 10.1136/emj.2007.048249.
  5. Goodacre S et al. The RATPAC (Randomised Assessment of Treatment using Panel Assay of Cardiac markers) trial: a randomised controlled trial of point-of-care cardiac markers in the emergency department.  Health Technol Assess 2011 May;15(23):iii-xi,1–102
  6. Rönnersten A, Haegerstam M, Schilling UM. Validation of the POC system iSTAT”. Akutdagarna 2011, Oct 20-21, Helsingborg, Sweden Conference Proceedings:30.
  7. Schilling UM, Haegerstam M, Rönnersten A.Time is money – the economic impact of POC on the ED. Akutdagarna 2011, Oct 20–21, Helsingborg, Sweden Conference Proceedings:27
  8. Ryan RJ et al. A multicenter randomized controlled trial comparing central laboratory and Point-of-Care Cardiac marker testing strategies: The Disposition Impacted by Serial Point-of-care Markers in Acute Coronary Syndromes (DISPO-ACS) Trial. Ann Emerg Med 2008;pp1-8. doi:10.1016/j.annemergmed.2008.06.464
  9. Venge P et al. Early and late outcome prediction of death in the emergency room by point-of-care and laboratory assays of cardiac troponin I. Am Heart J 2010;160:835–41.
  10. Di Serio F et al. Integration between point-of-care cardiac markers in an emergency/cardiology department and the central laboratory: methodological and preliminary clinical evaluation. Clin Chem Lab Med. 2005;43(2):202–9.