Search tips
Search criteria

Results 1-10 (10)

Clipboard (0)

Select a Filter Below

Year of Publication
1.  Prediction of Cardiovascular Risk Using Framingham, ASSIGN and QRISK2: How Well Do They Predict Individual Rather than Population Risk? 
PLoS ONE  2014;9(10):e106455.
The objective of this study was to evaluate the performance of risk scores (Framingham, Assign and QRISK2) in predicting high cardiovascular disease (CVD) risk in individuals rather than populations.
Methods and findings
This study included 1.8 million persons without CVD and prior statin prescribing using the Clinical Practice Research Datalink. This contains electronic medical records of the general population registered with a UK general practice. Individual CVD risks were estimated using competing risk regression models. Individual differences in the 10-year CVD risks as predicted by risk scores and competing risk models were estimated; the population was divided into 20 subgroups based on predicted risk. CVD outcomes occurred in 69,870 persons. In the subgroup with lowest risks, risk predictions by QRISK2 were similar to individual risks predicted using our competing risk model (99.9% of people had differences of less than 2%); in the subgroup with highest risks, risk predictions varied greatly (only 13.3% of people had differences of less than 2%). Larger deviations between QRISK2 and our individual predicted risks occurred with calendar year, different ethnicities, diabetes mellitus and number of records for medical events in the electronic health records in the year before the index date. A QRISK2 estimate of low 10-year CVD risk (<15%) was confirmed by Framingham, ASSIGN and our individual predicted risks in 89.8% while an estimate of high 10-year CVD risk (≥20%) was confirmed in only 48.6% of people. The majority of cases occurred in people who had predicted 10-year CVD risk of less than 20%.
Application of existing CVD risk scores may result in considerable misclassification of high risk status. Current practice to use a constant threshold level for intervention for all patients, together with the use of different scoring methods, may inadvertently create an arbitrary classification of high CVD risk.
PMCID: PMC4182667  PMID: 25271417
2.  Variability of antibiotic prescribing in patients with chronic obstructive pulmonary disease exacerbations: a cohort study 
The role of antibiotics in treating mild or moderate exacerbations in patients with acute chronic obstructive pulmonary disease (COPD) is unclear. The aims were to: (i) describe patient characteristics associated with acute exacerbations amongst a representative COPD population, (ii) explore the relationship between COPD severity and outcomes amongst patients with exacerbations, and (iii) quantify variability by general practice in prescribing of antibiotics for COPD exacerbations.
A cohort of 62,747 patients with COPD was identified from primary care general practices (GP) in England, and linked to hospital admission and death certificate data. Exacerbation cases were matched to three controls and characteristics compared using conditional logistic regression. Outcomes were compared using incidence rates and Cox regression, stratified by disease severity. Variability of prescribing at the GP level was evaluated graphically and by using multilevel models.
COPD severity was found to be associated with exacerbation and subsequent mortality (very severe vs. mild, odds ratio for exacerbation 2.12 [95%CI 19.5–2.32]), hazard ratio for mortality 2.14 [95%CI 1.59–2.88]). Whilst 61% of exacerbation cases were prescribed antibiotics, this proportion varied considerably between GP practices (interquartile range, 48–73%). This variation is greater than can be explained by patient characteristics alone.
There is significant variability between GP practices in the prescribing of antibiotics to COPD patients experiencing exacerbations. Combined with a lack of evidence on the effects of treatment, this supports the need and opportunity for a large scale pragmatic randomised trial of the prescribing of antibiotics for COPD patients with exacerbations, in order to clarify their effectiveness and long term outcomes whilst ensuring the representativeness of subjects.
PMCID: PMC3679783  PMID: 23724907
Chronic obstructive pulmonary disease; Disease exacerbation; Clinical practice variation; Anti-bacterial agents; Primary health care; General practice
3.  A simple score for estimating the long-term risk of fracture in patients with multiple sclerosis 
Neurology  2012;79(9):922-928.
To derive a simple score for estimating the long-term risk of osteoporotic and hip fracture in individual patients with MS.
Using the UK General Practice Research Database linked to the National Hospital Registry (1997–2008), we identified patients with incident MS (n = 5,494). They were matched 1:6 by year of birth, sex, and practice with patients without MS (control subjects). Cox proportional hazards models were used to calculate the long-term risk of osteoporotic and hip fracture. We fitted the regression model with general and specific risk factors, and the final Cox model was converted into integer risk scores.
In comparison with the FRAX calculator, our risk score contains several new risk factors that have been linked with fracture, which include MS, use of antidepressants, use of anticonvulsants, history of falling, and history of fatigue. We estimated the 5- and 10-year risks of osteoporotic and hip fracture in relation to the risk score. The C-statistic was moderate (0.67) for the prediction of osteoporotic fracture and excellent (0.89) for the prediction of hip fracture.
This is the first clinical risk score for fracture risk estimation involving MS as a risk factor.
PMCID: PMC3425841  PMID: 22895583
4.  Risk of Fracture with Thiazolidinediones: An Individual Patient Data Meta-Analysis 
Background: The use of thiazolidinediones (TZDs) has been associated with increased fracture risks. Our aim was to estimate the risk of fracture with TZDs in three different healthcare registries, using exactly the same study design, and to perform an individual patient data meta-analysis of these three studies.
Methods: Population-based cohort studies were performed utilizing the British General Practice Research Database (GPRD), the Dutch PHARMO Record Linkage System (RLS), and the Danish National Health Registers. In all three databases, the exposed cohort consisted of all patients (aged 18+) with at least one prescription of antidiabetic (AD) medication. Cox proportional hazards models were used to estimate hazard ratios (HRs) of fracture. The total period of follow-up for each patient was divided into periods of current exposure and past exposure, with patients moving between current and past use.
Results: In all three registries, the risk of fracture was increased for women who were exposed to TZDs: HR 1.48 (1.37–1.60) in GPRD, HR 1.35 (1.15–1.58) in PHARMO, and HR 1.22 (1.03–1.44) in Denmark. Combining the data in an individual patient data meta-analysis resulted, for women, in a 1.4-fold increased risk of any fracture for current TZD users versus other AD drug users [adj. HR 1.44 (1.35–1.53)]. For men, there was no increased fracture risk [adj. HR 1.05 (0.96–1.14)]. Risks were increased for fractures of the radius/ulna, humerus, tibia/fibula, ankle, and foot, but not for hip/femur or vertebral fractures. Current TZD users with more than 25 TZD prescriptions ever before had a 1.6-fold increased risk of fracture compared with other AD drug users [HR 1.59 (1.46–1.74)].
Conclusion: In this study, we consistently found a 1.2- to 1.5-fold increased risk of fractures for women using TZDs, but not for men, across three different healthcare registries. TZD users had an increased risk for fractures of the extremities, and risks further increased for prolonged users of TZDs.
PMCID: PMC3582108  PMID: 23549934
thiazolidinediones; fracture; individual patient data; meta-analysis; epidemiology
5.  Risk of Fracture with Thiazolidinediones: Disease or Drugs? 
Calcified Tissue International  2012;90(6):450-457.
The use of thiazolidinediones (TZDs) has been associated with an increased fracture risk. In addition, type 2 diabetes mellitus (T2DM) has been linked with fracture. We evaluated to what extent the association between TZD use and fracture risk is related to the drug or to the underlying disease. We conducted a population-based cohort study using the Danish National Health Registers (1996–2007), which link pharmacy data to the national hospital registry. Oral antidiabetic users (n = 180,049) were matched 1:3 by year of birth and sex to nonusers. Cox proportional hazards models were used to estimate hazard ratios (HRs) of fracture. Time-dependent adjustments were made for age, comorbidity, and drug use. We created a proxy indicator for the severity of disease. The first stage was defined as current use of either a biguanide or a sulfonyluerum, the second stage as current use of a biguanide and a sulfonyluerum at the same time, the third stage as patients using TZDs, and the fourth stage as patients using insulin. The risk of osteoporotic fracture was increased 1.3-fold for stages 3 and 4 compared with controls. Risk with current TZD use (stage 3 HR = 1.27, 95 % CI 1.06–1.52) and risk with current use of insulin (stage 4 HR = 1.25, 95 % CI 1.20–1.31) were similar. In the first (HR = 1.15, 95 % CI 1.13–1.18) and second (HR = 1.00, 95 % CI 0.96–1.04) stages risks were lower. Risk of osteoporotic fracture was similar for TZD users and insulin users. When studying fracture risk with TZDs, the underlying T2DM should be taken into account.
PMCID: PMC3349019  PMID: 22488176
Thiazolidinedione; Type 2 diabetes mellitus; Fracture risk; Osteoporosis
7.  A Comparison of Cost Effectiveness Using Data from Randomized Trials or Actual Clinical Practice: Selective Cox-2 Inhibitors as an Example 
PLoS Medicine  2009;6(12):e1000194.
Tjeerd-Pieter van Staa and colleagues estimate the likely cost effectiveness of selective Cox-2 inhibitors prescribed during routine clinical practice, as compared to the cost effectiveness predicted from randomized controlled trial data.
Data on absolute risks of outcomes and patterns of drug use in cost-effectiveness analyses are often based on randomised clinical trials (RCTs). The objective of this study was to evaluate the external validity of published cost-effectiveness studies by comparing the data used in these studies (typically based on RCTs) to observational data from actual clinical practice. Selective Cox-2 inhibitors (coxibs) were used as an example.
Methods and Findings
The UK General Practice Research Database (GPRD) was used to estimate the exposure characteristics and individual probabilities of upper gastrointestinal (GI) events during current exposure to nonsteroidal anti-inflammatory drugs (NSAIDs) or coxibs. A basic cost-effectiveness model was developed evaluating two alternative strategies: prescription of a conventional NSAID or coxib. Outcomes included upper GI events as recorded in GPRD and hospitalisation for upper GI events recorded in the national registry of hospitalisations (Hospital Episode Statistics) linked to GPRD. Prescription costs were based on the prescribed number of tables as recorded in GPRD and the 2006 cost data from the British National Formulary. The study population included over 1 million patients prescribed conventional NSAIDs or coxibs. Only a minority of patients used the drugs long-term and daily (34.5% of conventional NSAIDs and 44.2% of coxibs), whereas coxib RCTs required daily use for at least 6–9 months. The mean cost of preventing one upper GI event as recorded in GPRD was US$104k (ranging from US$64k with long-term daily use to US$182k with intermittent use) and US$298k for hospitalizations. The mean costs (for GPRD events) over calendar time were US$58k during 1990–1993 and US$174k during 2002–2005. Using RCT data rather than GPRD data for event probabilities, the mean cost was US$16k with the VIGOR RCT and US$20k with the CLASS RCT.
The published cost-effectiveness analyses of coxibs lacked external validity, did not represent patients in actual clinical practice, and should not have been used to inform prescribing policies. External validity should be an explicit requirement for cost-effectiveness analyses.
Please see later in the article for the Editors' Summary
Editors' Summary
Before a new treatment for a specific disease becomes an established part of clinical practice, it goes through a long process of development and clinical testing. This process starts with extensive studies of the new treatment in the laboratory and in animals and then moves into clinical trials. The most important of these trials are randomized controlled trials (RCTs), studies in which the efficacy and safety of the new drug and an established drug are compared by giving the two drugs to randomized groups of patients with the disease. The final hurdle that a drug or any other healthcare technology often has to jump before being adopted for widespread clinical use is a health technology assessment, which aims to provide policymakers, clinicians, and patients with information about the balance between the clinical and financial costs of the drug and its benefits (its cost-effectiveness). In England and Wales, for example, the National Institute for Health and Clinical Excellence (NICE), which promotes clinical excellence and the effective use of resources within the National Health Service, routinely commissions such assessments.
Why Was This Study Done?
Data on the risks of various outcomes associated with a new treatment are needed for cost-effectiveness analyses. These data are usually obtained from RCTs, but although RCTs are the best way of determining a drug's potency in experienced hands under ideal conditions (its efficacy), they may not be a good way to determine a drug's success in an average clinical setting (its effectiveness). In this study, the researchers compare the data from RCTs that have been used in several published cost-effectiveness analyses of a class of drugs called selective cyclooxygenase-2 inhibitors (“coxibs”) with observational data from actual clinical practice. They then ask whether the published cost-effectiveness studies, which generally used RCT data, should have been used to inform coxib prescribing policies. Coxibs are nonsteroidal anti-inflammatory drugs (NSAIDs) that were developed in the 1990s to treat arthritis and other chronic inflammatory conditions. Conventional NSAIDs can cause gastric ulcers and bleeding from the gut (upper gastrointestinal events) if taken for a long time. The use of coxibs avoids this problem.
What Did the Researchers Do and Find?
The researchers extracted data on the real-life use of conventional NSAIDs and coxibs and on the incidence of upper gastrointestinal events from the UK General Practice Research Database (GPRD) and from the national registry of hospitalizations. Only a minority of the million patients who were prescribed conventional NSAIDs (average cost per prescription US$17.80) or coxibs (average cost per prescription US$47.04) for a variety of inflammatory conditions took them on a long-term daily basis, whereas in the RCTs of coxibs, patients with a few carefully defined conditions took NSAIDs daily for at least 6–9 months. The researchers then developed a cost-effectiveness model to evaluate the costs of the alternative strategies of prescribing a conventional NSAID or a coxib. The mean additional cost of preventing one gastrointestinal event recorded in the GPRD by using a coxib instead of a NSAID, they report, was US$104,000; the mean cost of preventing one hospitalization for such an event was US$298,000. By contrast, the mean cost of preventing one gastrointestinal event by using a coxib instead of a NSAID calculated from data obtained in RCTs was about US$20,000.
What Do These Findings Mean?
These findings suggest that the published cost-effectiveness analyses of coxibs greatly underestimate the cost of preventing gastrointestinal events by replacing prescriptions of conventional NSAIDs with prescriptions of coxibs. That is, if data from actual clinical practice had been used in cost-effectiveness analyses rather than data from RCTs, the conclusions of the published cost-effectiveness analyses of coxibs would have been radically different and may have led to different prescribing guidelines for this class of drug. More generally, these findings provide a good illustration of how important it is to ensure that cost-effectiveness analyses have “external” validity by using realistic estimates for event rates and costs rather than relying on data from RCTs that do not always reflect the real-world situation. The researchers suggest, therefore, that health technology assessments should move from evaluating cost-efficacy in ideal populations with ideal interventions to evaluating cost-effectiveness in real populations with real interventions.
Additional Information
Please access these Web sites via the online version of this summary at
The UK National Institute for Health Research provides information about health technology assessment
The National Institute for Health and Clinical Excellence Web site describes how this organization provides guidance on promoting good health within the England and Wales National Health Service
Information on the UK General Practice Research Database is available
Wikipedia has pages on health technology assessment and on selective cyclooxygenase-2 inhibitors (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
PMCID: PMC2779340  PMID: 19997499
8.  Risk of fracture after bariatric surgery in the United Kingdom: population based, retrospective cohort study  
Objectives To estimate fracture risk in patients receiving bariatric surgery versus matched controls.
Design Population based, retrospective cohort study.
Setting Use of records from the United Kingdom General Practice Research Database, now known as the Clinical Practice Research Datalink (from January 1987 to December 2010).
Participants Patients with a body mass index of at least 30, with a record of bariatric surgery (n=2079), and matched controls without a record (n=10 442). Each bariatric surgery patient was matched to up to six controls by age, sex, practice, year, and body mass index. Patients were followed from the date of bariatric surgery for the occurrence of any fracture. We used time dependent Cox regression to calculate relative rates of fracture, adjusted for disease and previous drug treatment, and time-interaction terms to evaluate fracture timing patterns.
Main outcome measure Relative rates of any, osteoporotic, and non-osteoporotic fractures.
Results Mean follow-up time was 2.2 years. Overall, there was no significantly increased risk of fracture in patients who underwent bariatric surgery, compared with controls (8.8 v 8.2 per 1000 person years; adjusted relative risk 0.89, 95% confidence interval 0.60 to 1.33). Bariatric surgery also did not affect risk of osteoporotic and non-osteoporotic fractures. However, we saw a trend towards an increased fracture risk after three to five years following surgery, as well as in patients who had a greater decrease in body mass index after surgery, but this was not significant.
Conclusion Bariatric surgery does not have a significant effect on the risk of fracture. For the first few years after surgery, these results are reassuring for patients undergoing such operations, but do not exclude a more protracted adverse influence on skeletal health in the longer term.
PMCID: PMC3413006  PMID: 22867649
9.  The efficiency of cardiovascular risk assessment: do the right patients get statin treatment? 
Heart  2013;99(21):1597-1602.
To evaluate targeting of statin prescribing for primary prevention to those with high cardiovascular disease (CVD) risk.
Two cohort studies including the general population and initiators of statins aged 35–74 years.
UK primary care records in the Clinical Practice Research Datalink.
3.8 million general population patients and 300 914 statin users.
Statin prescribing.
Main outcome measures
Statin prescribing by CVD risk; observed 5-year CVD risks; variability between practices.
Statin prescribing increased substantially over time to patients with high 10-year CVD risk (≥20%): 7.0% of these received a statin prior to 2007, and 30.4% in 2007 onwards. Prescribing to patients with low risk (<15%) also increased (from 1.9% to 5.0%). Only about half the patients initiating statin treatment were high risk according to CVD risk score. The 5-year CVD risks, as observed during statin treatment, reduced over calendar time (from 17.0% to 7.1%). There was a large variation between general practices in the percentage of high-risk patients prescribed a statin in 2007 onwards, ranging from 8.2% to 61.5%. For low-risk patients, these varied from 2.1% to 29.1%.
There appeared to be substantive overuse in low CVD risk and underuse in high CVD risk (600 000 and 850 000 patients, respectively, in the UK since 2007). There is wide variation between practices in statin prescribing to patients at high CVD risk. There is a clear need for randomised trials for the best strategy to target statin treatment and manage CVD risk for primary prevention.
PMCID: PMC3812879  PMID: 23735939
10.  Pragmatic randomised trials using routine electronic health records: putting them to the test 
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 randomised trials of treatments in real time could provide the answer
PMCID: PMC3934788  PMID: 22315246

Results 1-10 (10)