***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND The benefit of CT coronary angiography ( CTCA ) in patients presenting with stable chest pain has not been systematic ally studied . We aim ed to assess the effect of CTCA on the diagnosis , management , and outcome of patients referred to the cardiology clinic with suspected angina due to coronary heart disease . METHODS In this prospect i ve open-label , parallel-group , multicentre trial , we recruited patients aged 18 - 75 years referred for the assessment of suspected angina due to coronary heart disease from 12 cardiology chest pain clinics across Scotl and . We r and omly assigned ( 1:1 ) participants to st and ard care plus CTCA or st and ard care alone . R and omisation was done with a web-based service to ensure allocation concealment . The primary endpoint was certainty of the diagnosis of angina secondary to coronary heart disease at 6 weeks . All analyses were intention to treat , and patients were analysed in the group they were allocated to , irrespective of compliance with scanning . This study is registered with Clinical Trials.gov , number NCT01149590 . FINDINGS Between Nov 18 , 2010 , and Sept 24 , 2014 , we r and omly assigned 4146 ( 42 % ) of 9849 patients who had been referred for assessment of suspected angina due to coronary heart disease . 47 % of participants had a baseline clinic diagnosis of coronary heart disease and 36 % had angina due to coronary heart disease . At 6 weeks , CTCA reclassified the diagnosis of coronary heart disease in 558 ( 27 % ) patients and the diagnosis of angina due to coronary heart disease in 481 ( 23 % ) patients ( st and ard care 22 [ 1 % ] and 23 [ 1 % ] ; p<0·0001 ) . Although both the certainty ( relative risk [ RR ] 2·56 , 95 % CI 2·33 - 2·79 ; p<0·0001 ) and frequency of coronary heart disease increased ( 1·09 , 1·02 - 1·17 ; p=0·0172 ) , the certainty increased ( 1·79 , 1·62 - 1·96 ; p<0·0001 ) and frequency seemed to decrease ( 0·93 , 0·85 - 1·02 ; p=0·1289 ) for the diagnosis of angina due to coronary heart disease . This changed planned investigations ( 15 % vs 1 % ; p<0·0001 ) and treatments ( 23 % vs 5 % ; p<0·0001 ) but did not affect 6-week symptom severity or subsequent admittances to hospital for chest pain . After 1·7 years , CTCA was associated with a 38 % reduction in fatal and non-fatal myocardial infa rct ion ( 26 vs 42 , HR 0·62 , 95 % CI 0·38 - 1·01 ; p=0·0527 ) , but this was not significant . INTERPRETATION In patients with suspected angina due to coronary heart disease , CTCA clarifies the diagnosis , enables targeting of interventions , and might reduce the future risk of myocardial infa rct ion . FUNDING The Chief Scientist Office of the Scottish Government Health and Social Care Directorates funded the trial with supplementary awards from Edinburgh and Lothian 's Health Foundation Trust and the Heart Diseases Research Fund BACKGROUND Many patients have symptoms suggestive of coronary artery disease ( CAD ) and are often evaluated with the use of diagnostic testing , although there are limited data from r and omized trials to guide care . METHODS We r and omly assigned 10,003 symptomatic patients to a strategy of initial anatomical testing with the use of coronary computed tomographic angiography ( CTA ) or to functional testing ( exercise electrocardiography , nuclear stress testing , or stress echocardiography ) . The composite primary end point was death , myocardial infa rct ion , hospitalization for unstable angina , or major procedural complication . Secondary end points included invasive cardiac catheterization that did not show obstructive CAD and radiation exposure . RESULTS The mean age of the patients was 60.8±8.3 years , 52.7 % were women , and 87.7 % had chest pain or dyspnea on exertion . The mean pretest likelihood of obstructive CAD was 53.3±21.4 % . Over a median follow-up period of 25 months , a primary end-point event occurred in 164 of 4996 patients in the CTA group ( 3.3 % ) and in 151 of 5007 ( 3.0 % ) in the functional-testing group ( adjusted hazard ratio , 1.04 ; 95 % confidence interval , 0.83 to 1.29 ; P=0.75 ) . CTA was associated with fewer catheterizations showing no obstructive CAD than was functional testing ( 3.4 % vs. 4.3 % , P=0.02 ) , although more patients in the CTA group underwent catheterization within 90 days after r and omization ( 12.2 % vs. 8.1 % ) . The median cumulative radiation exposure per patient was lower in the CTA group than in the functional-testing group ( 10.0 mSv vs. 11.3 mSv ) , but 32.6 % of the patients in the functional-testing group had no exposure , so the overall exposure was higher in the CTA group ( mean , 12.0 mSv vs. 10.1 mSv ; P<0.001 ) . CONCLUSIONS In symptomatic patients with suspected CAD who required noninvasive testing , a strategy of initial CTA , as compared with functional testing , did not improve clinical outcomes over a median follow-up of 2 years . ( Funded by the National Heart , Lung , and Blood Institute ; PROMISE Clinical Trials.gov number , NCT01174550 . ) OBJECTIVES The study aim was to determine observational differences in costs of care by the coronary disease diagnostic test modality . BACKGROUND A number of diagnostic strategies are available with few data to compare the cost implication s of the initial test choice . METHODS We prospect ively enrolled 11,372 consecutive stable angina patients who were referred for stress myocardial perfusion tomography or cardiac catheterization . Stress imaging patients were matched by their pretest clinical risk of coronary disease to a series of patients referred to cardiac catheterization . Composite 3-year costs of care were compared for two patients management strategies : 1 ) direct cardiac catheterization ( aggressive ) and 2 ) initial stress myocardial perfusion tomography and selective catheterization of high risk patients ( conservative ) . Analysis of variance techniques were used to compare costs , adjusting for treatment propensity and pretest risk . RESULTS Observational comparisons of aggressive as compared with conservative testing strategies reveal that costs of care were higher for direct cardiac catheterization in all clinical risk subsets ( range : $ 2,878 to $ 4,579 ) , as compared with stress myocardial perfusion imaging plus selective catheterization ( range : $ 2,387 to $ 3,010 , p < 0.0001 ) . Coronary revascularization rates were higher for low , intermediate and high risk direct catheterization patients as compared with the initial stress perfusion imaging cohort ( 13 % to 50 % , p < 0.0001 ) ; cardiac death or myocardial infa rct ion rates were similar ( p > 0.20 ) . CONCLUSIONS Observational assessment s reveal that stable chest pain patients who undergo a more aggressive diagnostic strategy have higher diagnostic costs and greater rates of intervention and follow-up costs . Cost differences may reflect a diminished necessity for re source consumption for patients with normal test results In patients with stable ischemic heart disease ( SIHD ) , myocardial revascularization should be performed to either improve survival or improve symptoms and functional status among patients who are not well controlled with optimal medical therapy ( OMT ) .  A general consensus exists on the core elements of OMT , which include both lifestyle intervention and intensive secondary prevention with proven pharmacotherapies . By contrast , however , there is less general agreement as to what constitutes the optimal approach to revascularization in SIHD patients . The COURAGE and FAME 2 r and omized trials form the foundation of the current clinical evidence base and raise the important question : “ What is the impact of myocardial ischemia on myocardial revascularization in stable ischemic heart disease?”ZusammenfassungBei Patienten mit stabiler ischämischer Herzkrankheit ( SIHD ) sollte eine myokardiale Revaskularisierung erfolgen , um entweder das Überleben oder die Symptome und den Funktionszust and bei Patienten zu verbessern , bei denen die Erkrankung trotz optimaler medikamentöser Therapie ( OMT ) nicht gut unter Kontrolle ist . Es besteht ein allgemeiner Konsens bei den Kernelementen der OMT , zu denen sowohl eine Änderung der Lebensweise als auch eine intensive Sekundärprävention mit bewährter Pharmakotherapie gehören . Dagegen besteht jedoch eine geringere Übereinstimmung hinsichtlich des optimalen Ansatzes für die Revaskularisierung bei SIHD-Patienten . Die r and omisierten Studien COURAGE und FAME 2 bilden die Grundlage der aktuellen klinischen Evidenzbasierung und werfen die wichtige Frage auf : „ Wie beeinflusst die Myokardischämie eine myokardiale Revaskularisierung bei stabiler ischämischer Herzkrankheit ? OBJECTIVES To assess the acceptability and feasibility of functional tests as a gateway to angiography for management of coronary artery disease ( CAD ) , the ability of diagnostic strategies to identify patients who should undergo revascularisation , patient outcomes in each diagnostic strategy , and the most cost-effective diagnostic strategy for patients with suspected or known CAD . DESIGN A rapid systematic review of economic evaluations of alternative diagnostic strategies for CAD was carried out . A pragmatic and generalisable r and omised controlled trial was undertaken to assess the use of the functional cardiac tests : angiography ( controls ) ; single photon emission computed tomography ( SPECT ) ; magnetic resonance imaging ( MRI ) ; stress echocardiography . SETTING The setting was Papworth Hospital NHS Foundation Trust , a tertiary cardiothoracic referral centre . PARTICIPANTS Patients with suspected or known CAD and an exercise test result that required non-urgent angiography . INTERVENTIONS Patients were r and omised to one of the four initial diagnostic tests . MAIN OUTCOME MEASURES Eighteen months post-r and omisation : exercise time ( modified Bruce protocol ) ; cost-effectiveness compared with angiography ( diagnosis , treatment and follow-up costs ) . The aim was to demonstrate equivalence in exercise time between those r and omised to functional tests and those r and omised to angiography [ defined as the confidence interval ( CI ) for mean difference from angiography within 1 minute ] . RESULTS The 898 patients were r and omised to  angiography  ( n = 222 ) , SPECT ( n = 224 ) , MRI ( n = 226 ) or stress echo ( n = 226 ) . Initial diagnostic tests were completed successfully with unequivocal results for 98 % of angiography , 94 % of SPECT ( p = 0.05 ) , 78 % of MRI ( p < 0.001 ) and 90 % of stress echocardiography patients ( p < 0.001 ) . Some 22 % of SPECT patients , 20 % of MRI patients and 25 % of stress echo patients were not subsequently referred for an angiogram . Positive functional tests were confirmed by positive angiography in 83 % of SPECT patients , 89 % of MRI patients and 84 % of stress echo patients . Negative functional tests were followed by positive angiograms in 31 % of SPECT patients , 52 % of MRI patients and 48 % of stress echo patients tested . The proportions that had coronary artery bypass graft surgery were 10 % ( angiography ) , 11 % ( MRI ) and 13 % ( SPECT and stress echo ) and percutaneous coronary intervention 25 % ( angiography ) , 18 % ( SPECT ) and 23 % ( MRI and stress echo ) . At 18 months , comparing SPECT and stress echo with angiography , a clinical ly significant difference in total exercise time can be ruled out . The MRI group had significantly shorter mean total exercise time of 35 seconds and the upper limit of the CI was 1.14 minutes less than in the angiography group , so a difference of at least 1 minute can not be ruled out . At 6 months post-treatment , SPECT and angiography had equivalent mean exercise time . Compared with angiography , the MRI and stress echo groups had significantly shorter mean total exercise time of 37 and 38 seconds , respectively , and the upper limit of both CIs was 1.16 minutes , so a difference of at least 1 minute can not be ruled out . The differences were mainly attributable to revascularised patients . There were significantly more non-fatal adverse events in the stress echo group , mostly admissions for chest pain , but no significant difference in the number of patients reporting events . Mean ( 95 % CI ) total additional costs over 18 months , compared with angiography , were 415 pounds ( -310 pounds to 1084 pounds ) for SPECT , 426 pounds ( -247 pounds to 1088 pounds ) for MRI and 821 pounds ( 10 pounds to 1715 pounds ) for stress echocardiography , with very little difference in quality -adjust 
    Output:
    
Nonetheless , the findings from this systematic review suggest that for patients with a low to intermediate prior probability of having obstructive CAD , computed tomography coronary angiography ( CTCA ) may be cost-effective as an initial diagnostic imaging test in comparison with CAG or other non-invasive diagnostic tests .
If functional testing is required , stress echocardiography ( SE ) or single-photon emission computed tomography ( SPECT ) are suggested to be cost-effective initial strategies in patients with intermediate prior probability of CAD .
Immediate CAG is suggested to be a cost-effective strategy for patients at a high prior probability of having obstructive CAD whom may benefit from revascularization .
The study emphasizes the inextricable link between clinical effectiveness and economic efficiency .
Evidence suggests that the optimal diagnostic imaging strategy for individuals suspected of having CAD is CTCA for low and intermediate disease probability , followed by SE or SPECT as necessary , and invasive CAG for high disease probability .