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BMJ 2004;328:254 (31 January), doi:10.1136/bmj.37956.664236.EE (published 14 January 2004)
Steve Goodacre, senior lecturer in health service research and emergency medicine1, Jon Nicholl, director, Medical Care Research Unit1, Simon Dixon, senior lecturer in health economics1, Elizabeth Cross, research associate1, Karen Angelini, chest pain nurse2, Jane Arnold, chest pain nurse2, Sue Revill, chest pain nurse2, Tom Locker, specialist registrar2, Simon J Capewell, chair of clinical epidemiology4, Deborah Quinney, research fellow4, Stephen Campbell, consultant3, Francis Morris, consultant2
1 School of Health and Related Research, University of Sheffield, Sheffield S1 4DA, 2 Emergency Department, Northern General Hospital, Sheffield S5 7AU, 3 Department of Cardiology, Northern General Hospital, 4 Department of Public Health, University of Liverpool, Liverpool L69 3GB
Correspondence to: S Goodacre s.goodacre{at}sheffield.ac.uk
Design Cluster randomised controlled trial, with 442 days randomised to the chest pain observation unit or routine care, and cost effectiveness analysis from a health service costing perspective.
Setting The emergency department at the Northern General Hospital, Sheffield, United Kingdom.
Participants 972 patients with acute, undifferentiated chest pain (479 attending on days when care was delivered in the chest pain observation unit, 493 on days of routine care) followed up until six months after initial attendance.
Main outcome measures The proportion of participants admitted to hospital, the proportion with acute coronary syndrome sent home inappropriately, major adverse cardiac events over six months, health utility, hospital reattendance and readmission, and costs per patient to the health service.
Results Use of a chest pain observation unit reduced the proportion of patients admitted from 54% to 37% (difference 17%, odds ratio 0.50, 95% confidence interval 0.39 to 0.65, P < 0.001) and the proportion discharged with acute coronary syndrome from 14% to 6% (8%, -7% to 23%, P = 0.264). Rates of cardiac event were unchanged. Care in the chest pain observation unit was associated with improved health utility during follow up (0.0137 quality adjusted life years gained, 95% confidence interval 0.0030 to 0.0254, P = 0.022) and a saving of £78 per patient (-£56 to £210, P = 0.252).
Conclusions Care in a chest pain observation unit can improve outcomes and may reduce costs to the health service. It seems to be more effective and more cost effective than routine care.
We aimed to evaluate the effectiveness and cost effectiveness of care in a chest pain observation unit. The specific objectives were to measure the effect of care in the chest pain observation unit on admission to hospital for undifferentiated chest pain, inappropriate discharge home with acute coronary syndrome, health utility, major adverse cardiac events, and reattendance at and readmission to hospital; and to measure the cost effectiveness of care in the chest pain observation unit compared with routine care.
Intervention: chest pain observation unit
The chest pain observation unit was based in the emergency department and consisted of two monitored bays and an adjacent area of unmonitored bays. It was staffed by three chest pain nurses providing care from 9 00 am to 9 00 pm Monday to Friday, and 10 00 am to 6 00 pm at weekends. Patients attending outside these hours could be admitted and complete their assessment the following day. Middle grade emergency department staff provided medical cover.
We selected patients according to validated clinical predictors3 4 and offered assessment consisting of two to six hours of ST segment monitoring5 and hourly electrocardiography, measurement of biochemical cardiac markers (CK-MB(mass) on arrival and at least two hours later,6 and troponin T at least six hours after onset of symptoms),7 and exercise treadmill testing.8 Patients with positive tests were admitted; those with negative tests were discharged.
Control: routine care
Patients were managed at the discretion of the emergency department medical staff. The emergency department has access to CK-MB(mass) and troponin T assays with a turnaround time of one hour. If patients required observation or further testing they were admitted to hospital.
Reception staff recorded the presenting complaint of all patients attending the emergency department. The chest pain nurses then identified all patients presenting with a specific list of chest pain related complaints and excluded patients with changes to their electrocardiogram that were diagnostic for acute coronary syndrome, clinically diagnosed unstable angina, comorbidity, or a serious alternative cause for chest pain; and patients who were younger than 25, with a negligible risk of coronary heart disease, or who were unable to take part in the trial or provide consent.
Follow up consisted of a clinic run by the chest pain nurses some 48 hours after initial attendance, at which an electrocardiogram was recorded and troponin T concentration measured. Postal questionnaires for completion by each patient were provided at 48 hours and one month, for return to the medical care research unit. At six months we searched the hospital computer system for evidence of attendance at the emergency department or admission to hospital, and reviewed the case notes. Finally, a research assistant telephoned each participant to collect further follow up information.
The primary outcome was the proportion of participants admitted to hospital. A key secondary outcome was the proportion of patients with acute coronary syndrome who were discharged home inappropriately. We defined acute coronary syndrome as a raised concentration of troponin T (> 0.03 ng/ml) at follow up. Other outcome measures were the major adverse cardiac event rate (cardiac death, life threatening arrhythmia, heart failure requiring admission to hospital, non-fatal myocardial infarction, or revascularisation procedure); health utility, as measured by the EQ-5D questionnaire at two days, one month, and six months; and reattendance at or readmission to hospital.
Cost effectiveness analysis
We identified and measured costs from a health service perspective. Over the following six months we measured use of resources related to the initial attendance: care in the emergency department, initial admission to hospital, reviews of outpatients, investigations related to chest pain, reattendances, readmissions, and cardiac procedures. To value resources we used UK national unit costs where available9
10 and local costs elsewhere.
We used EQ-5D and six month survival data to measure outcomes. We calculated the area under the curve for health utility to generate estimates of quality adjusted life years (QALYs) accrued over six months. We used regression to impute missing data and undertook a sensitivity analysis to explore the effect of using different methods for handling missing data. We compared the costs and outcomes for care in the chest pain observation unit with routine care, and estimated the incremental cost effectiveness of care in the chest pain observation unit.
Statistical analysis
The principal analysis used multilevel random effects modelling to adjust for clustering by day of week, but not confounding. Secondary analysis adjusted for potential confounding by age, sex, and history of coronary heart disease (determined a priori to be potentially important prognostic factors) and any other characteristic that either showed significant baseline imbalance or predicted outcome. We derived cost effectiveness estimates from 1000 bootstrap estimates of the difference between the mean costs and QALYs accrued after care in the chest pain observation unit and routine care.
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The proportion admitted was 36.7% (176/479) of patients receiving care in the chest pain observation unit and 53.8% (265/493) receiving routine care (odds ratio 0.5, 95% confidence interval 0.39 to 0.65, P < 0.001, intraclass correlation coefficient = 0.001). Adjustment for confounding did not alter this result (adjusted odds ratio 0.49, 0.36 to 0.65, P < 0.001).
Seventy patients had a raised concentration of troponin T at follow up (mean concentration 0.65 ng/ml, median concentration 0.29 ng/ml, 57/70 (81.4%) > 0.1 ng/ml). Seven (10%) had been discharged home: 2/34 (5.9%) who received care in the chest pain observation unit and 5/36 (13.9%) who received routine care (difference 8.0%, -7.3% to 23.4%, P = 0.264).
A total of 35 patients had a major adverse cardiac event during follow up (3.6%): 18 (3.8%) from the group receiving care in the chest pain observation unit and 17 (3.4%) from the group receiving routine care (difference 0.4%, -2.0 to 2.7, P = 0.796).
From the EQ-5D scores, the mean area under the curve for health utility was calculated to be 0.3936 QALYs after care in the chest pain observation unit and 0.3799 QALYs after routine care (difference 0.0137 QALYs, 95% confidence interval 0.0030 to 0.0254, P = 0.022; adjusted difference 0.0143 QALYs, 0.0031 to 0.0255, P = 0.012). The intraclass correlation coefficient was zero for all health utility analyses. The results were robust to sensitivity analysis according to the method of handling missing data.
Over the six month follow up period, 61 participants (12.7%) in the group receiving care in the chest pain observation unit and 85 (17.2%) in the group receiving routine care reattended the emergency department (odds ratio for reattendance after chest pain observation unit care 0.65, P = 0.05; adjusted odds ratio 0.66, P = 0.061). Over the same time, 37 participants (7.7%) in the chest pain observation unit group and 52 (10.5%) in the routine care group were readmitted to hospital (odds ratio 0.67, P = 0.122; adjusted odds ratio 0.65, P = 0.126).
The mean cost per patient for chest pain related care over six months was £478 for the chest pain observation unit group and £556 for the routine care group (difference £78 per patient, -£56 to £210, P = 0.252; intraclass correlation coefficient = 0.046; adjusted difference £53 per patient, -£88 to £194, P = 0.462). The table shows the breakdown of costs. Higher initial costs for care in the chest pain observation unit were offset by lower costs for hospital admission and follow up.
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Figure 2 shows the cost effect pairs plotted on the cost effectiveness plane.11 Each represents a bootstrap estimate of the difference in mean cost (y axis) and mean effect (x axis) of care in the chest pain observation unit compared with routine care (positive values indicate that the chest pain observation unit is more effective and more expensive). This shows that, although care in the chest pain observation unit is very likely to be more effective than routine care, considerable uncertainty prevails regarding comparative costs, with the 95% confidence interval including the possibility of the chest pain observation unit being more expensive. However, if we are willing to pay £2750 per QALY gained by care in the chest pain observation unit then the probability that the chest pain observation unit will be considered cost effective is 95%.12
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Cost effectiveness
From an economic viewpoint, mean estimates show that the chest pain observation unit provides improved outcomes at lower cost. Substantial uncertainty surrounds the cost estimate. The chest pain observation unit may be more expensive. If it is, there is a 95% probability that the chest pain observation unit will be cost effective, given willingness to pay £2750 per QALY gained. This is much lower than the value of £30 000 per QALY that seems to guide decision making by the National Institute for Clinical Excellence.12
Comparison with other studies
Previous studies of cost effectiveness have compared care in a chest pain observation unit with inpatient treatment.13-15 Our study shows that such a comparison is inappropriate because 46% of the patients receiving routine care were not admitted to hospital. Consequently, the estimated cost savings generated by our study were lower and subject to greater uncertainty than previous estimates. We showed noteworthy improvements in health utility associated with the chest pain observation unit. These data cannot explain why, but the chest pain observation unit may provide greater reassurance through a more rigorous diagnostic work-up. If this is so, the chest pain observation unit may be justified by improving outcome, rather than simply reducing costs.
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Limitations
Since randomisation takes place before recruitment and consent to participate, it is possible for selection bias to influence results. We attempted to reduce this possibility by rigorous recording of selection criteria and by adjusting for known confounders in secondary analyses. This cannot, however, completely rule out the potential influence of selection bias. Secondly, since it is impossible to blind participants to the fact that they are receiving care in the chest pain observation unit or routine care, it is possible that a measure reported by patients, such as the EQ-5D, may be influenced by the patients' awareness that they are receiving "new" or routine care. Finally, further research is required before we can generalise the results from the Northern General chest pain observation unit to other hospitals.16
This is the abridged version of an article that was posted on bmj.com on 14 January 2004: http://bmj.com/cgi/doi/10.1136/bmj.37956.664236.EE Acknowledgments: We thank the staff of the Northern General Hospital departments of emergency medicine, acute medicine, and cardiology for their help with this project. We thank Brian Morris for support with chemical pathology services and Stephen Walters for additional statistical advice
Contributors: See bmj.com
Funding: The Northern General Hospital received a grant of £94 000 from the Department of Health to establish the chest pain observation unit. The study was supported by a £30 000 grant from NHS Trent Policy and Practice research funds. SG was funded by a NHS Trent Health Services research fellowship. DQ was funded by Merseyside Health Action Zone.
Competing interests: SG, FM, SC, KA, JA, SR, and TL were involved in establishing and developing the Northern General Hospital chest pain observation unit. KA, JA, and SR are currently employed as chest pain nurses running this chest pain observation unit. JN, SD, EC, SJC, and DQ have no competing interests to declare.
Ethical approval: North Sheffield Research Ethics Committee.
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