***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: Objectives To assess the completeness and representativeness of body mass index ( BMI ) data in the Clinical Practice Research Data link ( CPRD ) , and determine an optimal strategy for their use . Design Descriptive study . Setting Electronic healthcare records from primary care . Participants A million patient r and om sample from the UK CPRD primary care data base , aged ≥16 years . Primary and secondary outcome measures BMI completeness in CPRD was evaluated by age , sex and calendar period . CPRD-based summary BMI statistics for each calendar year ( 2003–2010 ) were age-st and ardised and sex-st and ardised and compared with equivalent statistics from the Health Survey for Engl and ( HSE ) . Results BMI completeness increased over calendar time from 37 % in 1990–1994 to 77 % in 2005–2011 , was higher among females and increased with age . When BMI at specific time points was assigned based on the most recent record , calendar – year-specific mean BMI statistics underestimated equivalent HSE statistics by 0.75–1.1 kg/m2 . Restriction to those with a recent ( ≤3 years ) BMI result ed in mean BMI estimates closer to HSE ( ≤0.28 kg/m2 underestimation ) , but excluded up to 47 % of patients . An alternative strategy of imputing up-to- date BMI based on modelled changes in BMI over time since the last available record also led to mean BMI estimates that were close to HSE ( ≤0.37 kg/m2 underestimation ) . Conclusions Completeness of BMI  in CPRD increased over time and varied by age and sex . At a given point in time , a large proportion of the most recent BMI s are unlikely to reflect current BMI ; consequent BMI misclassification might be reduced by employing model-based imputation of current BMI Background Asthma is a chronic lung disease in which recurrent asthma symptoms create a substantial burden to individuals and their families . At the same time the economic burden associated with asthma is considerable . Methods The cost-effectiveness study was part of a single centre prospect i ve r and omised controlled trial comparing a nurse-led telemonitoring programme to usual care in a population of asthmatic out patients . The study included 109 asthmatic out patients ( 56 children ; 53 adults ) . The duration of follow-up was 12 months , and measurements were performed at baseline , 4 , 8 , and 12 months . Patients were asked to transfer their monitor data at least twice daily and by judging the received data and following a stepwise intervention protocol a nurse was able to act as the main caregiver in the intervention group . In both groups the EQ-5D and the SF-6D were used to obtain estimates of health state utilities . One year health care costs , patient and family costs , and productivity losses were calculated . The mean incremental costs were weighted against the mean incremental effect in terms of QALY . Results The study population generally represented mild to moderate asthmatics . No significant differences were found between the groups with regard to the generic quality of life . Overall , the mean health care costs per patient were higher in the intervention group than in the control group . The intervention costs mainly caused the cost difference between the groups . The intervention costs the society € 31,035/QALY gained with regard to adults and with regard to children € 59,071/QALY gained . Conclusion If the outcome is measured by generic quality of life the nurse-led telemonitoring programme is of limited cost-effectiveness in the study population . From the societal perspective the probability of the programme being cost-effective compared to regular care was 85 % at a ceiling ratio of € 80,000/QALY gained among the adults and 68 % among the children . A decrease in the price of the asthma monitor will substantial increase the probability of the programme to be cost-effective . Trial registration Number : What to prescribe for a patient in general practice when the choice of treatments has a limited evidence base ? Tjeerd-Pieter van Staa and colleagues argue that using electronic health records to enter patients into r and omised trials of treatments in real time could provide the The aim of the present study was to quantify the  healthcare utilization  of a child population according to level of respiratory illness . A stratified r and om sample of 713 children was selected from respondents to a postal respiratory question naire , carried out in two general practice population s in 1993 . Children were stratified into four groups according to the number of positive responses to five key questions . These groups were used as indicators of likelihood of asthma diagnosis . A search was made of these childrens ' practice records covering a 2-yr period , to include both primary and secondary healthcare . There was a significant increase across positive response groups in the proportion of children having primary and secondary care based consultations , particularly for respiratory conditions ( p = 0.001 ) . There was also a significant increase in prescribing . Of those children considered to be " likely asthmatics " from their question naire responses , 8.1 % ( n = 31 ) did not receive any primary or secondary care for a respiratory problem over the 2-yr period . As the likelihood of respiratory illness increased in this population , more dem and was made upon re sources for the treatment of respiratory illness . Quantification of this dem and enables evidence based re source allocation decisions to be made . This method of quantification could be applied in other population Objective To determine the completeness and diagnostic validity of myocardial infa rct ion recording across four national health record sources in primary care , hospital care , a disease registry , and mortality register . Design Cohort study . Participants 21 482 patients with acute myocardial infa rct ion in Engl and between January 2003 and March 2009 , identified in four prospect ively collected , linked electronic health record sources : Clinical Practice Research Data link ( primary care data ) , Hospital Episode Statistics ( hospital admissions ) , the disease registry MINAP ( Myocardial Ischaemia National Audit Project ) , and the Office for National Statistics mortality register ( cause specific mortality data ) . Setting One country ( Engl and ) with one health system ( the National Health Service ) . Main outcome measures Recording of acute myocardial infa rct ion , incidence , all cause mortality within one year of acute myocardial infa rct ion , and diagnostic validity of acute myocardial infa rct ion compared with electrocardiographic and troponin findings in the disease registry ( gold st and ard ) . Results Risk factors and non-cardiovascular coexisting conditions were similar across patients identified in primary care , hospital admission , and registry sources . Immediate all cause mortality was highest among patients with acute myocardial infa rct ion recorded in primary care , which ( unlike hospital admission and disease registry sources ) included patients who did not reach hospital , but at one year mortality rates in cohorts from each source were similar . 5561 ( 31.0 % ) patients with non-fatal acute myocardial infa rct ion were recorded in all three sources and 11 482 ( 63.9 % ) in at least two sources . The crude incidence of acute myocardial infa rct ion was underestimated by 25 - 50 % using one source compared with using all three sources . Compared with acute myocardial infa rct ion defined in the disease registry , the positive predictive value of acute myocardial infa rct ion recorded in primary care was 92.2 % ( 95 % confidence interval 91.6 % to 92.8 % ) and in hospital admissions was 91.5 % ( 90.8 % to 92.1 % ) . Conclusion Each data source missed a substantial proportion ( 25 - 50 % ) of myocardial infa rct ion events . Failure to use linked electronic health records from primary care , hospital care , disease registry , and death certificates may lead to biased estimates of the incidence and outcome of myocardial infa rct ion . Trial registration NCT01569139 clinical trials.gov BACKGROUND acute medical units allow for those who need admission to be correctly identified , and for those who could be managed in ambulatory setting s to be discharged . However , re-admission rates for older people following discharge from acute medical units are high and may be associated with substantial health and social care costs . OBJECTIVE identifying patient-level health and social care costs for older people discharged from acute medical units in Engl and . DESIGN a prospect i ve cohort study of health and social care re source use . SETTING an acute medical unit in Nottingham , Engl and . PARTICIPANTS four hundred and fifty-six people aged over 70 who were discharged from an acute medical unit within 72 h of admission . METHODS hospitalisation and social care data were collected for 3 months post-recruitment . In Nottingham , further approvals were gained to obtain data from general practice s , ambulance services , intermediate care and mental healthcare . Re source use was combined with national unit costs . RESULTS costs from all sectors were available for 250 participants . The mean ( 95 % CI , median , range ) total cost was £ 1926 ( 1579 - 2383 , 659 , 0 - 23,612 ) . Contribution was : secondary care ( 76.1 % ) , primary care ( 10.9 % ) , ambulance service ( 0.7 % ) , intermediate care ( 0.2 % ) , mental healthcare ( 2.1 % ) and social care ( 10.0 % ) . The costliest 10 % of participants accounted for 50 % of the cost . CONCLUSIONS this study highlights the costs accrued by older people discharged from acute medical units ( AMUs ) : they are mainly ( 76 % ) in secondary care and half of all costs were incurred by a minority of participants ( 10 % ) Objectives The Hospital Episode Statistics ( HES ) data set is a source of administrative ‘ big data ’ with potential for costing purpose s in economic evaluations alongside clinical trials . This study assesses the validity of coverage in the HES outpatient data set . Methods Men who died of , or with , prostate cancer were selected from a prostate-cancer screening trial ( CAP , Cluster r and omised triAl of PSA testing for Prostate cancer ) . Details of visits that took place after 1/4/2003 to hospital outpatient departments for conditions related to prostate cancer were extracted from medical records ( MR ) ; these appointments were sought in the HES outpatient data set based on date . The matching procedure was repeated for periods before and after 1/4/2008 , when the HES outpatient data set was accredited as a national statistic . Results 4922 outpatient appointments were extracted from MR for 370 men . 4088 appointments recorded in MR were identified in the HES outpatient data set ( 83.1 % ; 95 % confidence interval [ CI ] 82.0–84.1 ) . For appointments occurring prior to 1/4/2008 , 2195/2755 ( 79.7 % ; 95 % CI 78.2–81.2 ) matches were observed , while 1893/2167 ( 87.4 % ; 95 % CI 86.0–88.9 ) appointments occurring after 1/4/2008 were identified ( p for difference < 0.001 ) . 215/370 men ( 58.1 % ) had at least one appointment in the MR review that was unmatched in HES , 155 men ( 41.9 % ) had all their appointments identified , and 20 men ( 5.4 % ) had no appointments identified in HES . Conclusions The HES outpatient data set appears reasonably valid for research , particularly following accreditation . The data set may be a suitable alternative to collecting MR data from hospital notes within a trial , although caution should be exercised with data collected prior to accreditation Background Poor outcomes and high re source -use are observed for frail older people discharged from acute medical units . A specialist geriatric medical intervention , to facilitate Comprehensive Geriatric Assessment , was developed to reduce the incidence of adverse outcomes and associated high re source -use in this group in the post-discharge period . Objective To examine the costs and cost-effectiveness of a specialist geriatric medical intervention for frail older people in the 90 days following discharge from an acute medical unit , compared with st and ard care . Methods Economic evaluation was conducted alongside a two-centre r and omised controlled trial ( AMIGOS ) . 433 patients ( aged 70 or over ) at risk of future health problems , discharged from acute medical units within 72 hours of attending hospital , were recruited in two general hospitals in Nottingham and Leicester , UK . Participants were r and omised to the intervention , comprising geriatrician assessment in acute units and further specialist management , or to control where patients received no additional intervention over and above st and ard care . Primary outcome was incremental cost per quality adjusted life year ( QALY ) gained . Results We undertook cost-effectiveness analysis for 417 patients ( intervention : 205 ) . The difference in mean adjusted QALYs gained between groups at 3 months was -0.001 ( 95 % confidence interval [ CI ] : -0.009 , 0.007 ) . Total adjusted secondary and social care costs , including direct costs of the intervention , at 3 months were £ 4412 ( € 5624 , $ 6878 ) and £ 4110 ( € 5239 , $ 6408 ) for the intervention and st and ard care groups , the incremental cost was £ 302 ( 95 % CI : 193 , 410 ) [ € 385 , $ 471 ] . The intervention was dominated by st and ard care with probability of 62 % , and with 0 % probability of cost-effectiveness ( at £ 20,000/QALY threshold ) . Conclusions The specialist ger 
    Output:
    
Conclusion Economic evaluations using data from a large observational data base without any primary data collection is feasible , informative and potentially efficient .