Confounding by indication and channeling over time: the risks of beta 2-agonists

Real World Data Studies of Antineoplastic Drugs: How Can They Be Improved to Steer Everyday Use in the Clinic?

There is a growing interest in real world evidence when developing antineoplastic drugs owing to the shorter length of time and low costs compared to randomised controlled trials. External validity of studies in the regulatory phase can be enhanced by complementing randomised controlled trials with real world evidence. Furthermore, the use of real world evidence ensures the inclusion of patients often excluded from randomised controlled trials such as the elderly, certain ethnicities or those from certain geographical areas. This review explores approaches in which real world data may be integrated with randomised controlled trials. One approach is by using big data, especially when investigating drugs in the antineoplastic setting. This can even inform artificial intelligence thus ensuring faster and more precise diagnosis and treatment decisions. Pragmatic trials also offer an approach to examine the effectiveness of novel antineoplastic drugs without evading the benefits of randomised controlled trials. A well-designed pragmatic trial would yield results with high external validity by employing a simple study design with a large sample size and diverse settings. Although randomised controlled trials can determine efficacy of antineoplastic drugs, effectiveness in the real world may differ. The need for pragmatic trials to help guide healthcare decision-making led to the development of trials within cohorts (TWICs). TWICs make use of cohorts to conduct multiple randomised controlled trials while maintaining characteristics of real world data in routine clinical practice. Although real world data is often affected by incomplete data and biases such as selection and unmeasured biases, the use of big data and pragmatic approaches can improve the use of real world data in the development of antineoplastic drugs that can in turn steer decision-making in clinical practice.

The association of melatonin use and hip fracture: a matched cohort study

By using propensity-score matched cohorts, we compared the risk of incident hip fracture between melatonin initiators and hypnotic benzodiazepines initiators. The initiation of melatonin was not associated with an increased risk of hip fracture.

INTRODUCTION

Melatonin is hypothesized to suppress bone loss, but a previous study reported an increased risk of hip fracture among melatonin users compared with non-users, which was however susceptible to confounding by indication. This study aimed to compare the risk of hip fracture between melatonin initiators and initiators of its active comparators, i.e., hypnotic benzodiazepines.

METHODS

Among individuals aged 40 years or older without a history of hip fracture or cancer in the IQVIA Medical Research Database (IMRD) in the UK (2000-2018), a propensity score-matched cohort study was conducted to examine the association of melatonin initiation vs. hypnotic benzodiazepines initiation with the risk of hip fracture.

RESULTS

After propensity score matching, 9,038 patients were included (4,519 melatonin initiators and 4,519 hypnotic benzodiazepines initiators). During the entire follow-up, 41 cases of hip fracture occurred in the melatonin cohort, and 51 cases occurred in the hypnotic benzodiazepines cohort. The absolute rate difference in hip fracture between melatonin initiators and hypnotic benzodiazepines initiators was -0.8 (95% CI: -1.9 to 0.3) per 1000 person-years and the multivariable-adjusted hazard ratio (HR) of hip fracture for melatonin initiators was 0.78 (95% CI: 0.51 to 1.17).

CONCLUSION

In this population-based cohort study, the risk of hip fracture among melatonin initiators was not higher, if not lower, than that among hypnotic benzodiazepines initiators.

Real-World Impact of Nonclinical Inhaler Regimen Switches on Asthma or COPD: A Systematic Review

BACKGROUND

Switching inhaler regimens can be driven by poor disease control but also by nonclinical factors, such as cost and environmental impact. The consequences of switching for nonclinical reasons are largely unclear.

OBJECTIVE

To systematically review the real-world consequences of switching inhaler regimens for nonclinical reasons in asthma and/or chronic obstructive pulmonary disease patients.

METHODS

Embase, MEDLINE, EBM Reviews, and EconLit were searched to November 21, 2020. Conference searches and reference checking were also performed. Real-world studies of asthma and/or chronic obstructive pulmonary disease patients undergoing a switch in inhaler regimen for any reason apart from clinical need were included. Two reviewers screened and extracted data. Key outcomes included symptom control, exacerbations, and patient-doctor relationships.

RESULTS

A total of 8,958 records were screened and 21 studies included. Higher-quality (matched comparative) studies were prioritized. Five matched studies (6 datasets) reported on symptom control: 5 datasets (n = 7,530) with unclear patient consent reported improved disease control following switching, and 1 dataset (n = 1,648) with non-consented patients reported significantly worsened disease control. Three matched studies (5 datasets, n = 10,084) reported on exacerbation rate ratios; results were heterogeneous depending on the definition used. Two studies (n = 137) reported that switching inhaler regimens could have a negative impact on the doctor-patient relationship, especially when the switches were non-consented. Study quality was generally low.

CONCLUSIONS

Switching inhaler regimens is a complex issue that can have variable clinical consequences and can harm the patient-doctor relationship. Limited high-quality evidence was identified, and study designs were heterogeneous. A robust framework is needed to guide the personalized switching of inhalers.

A Description of COVID-19-Directed Therapy in Children Admitted to US Intensive Care Units 2020

BACKGROUND

It is unclear how acute coronavirus disease 2019 (COVID-19)-directed therapies are used in children with life-threatening COVID-19 in US hospitals. We described characteristics of children hospitalized in the intensive care unit or step-down unit (ICU/SDU) who received COVID-19-directed therapies and the specific therapies administered.

METHODS

Between March 15, 2020 and December 27, 2020, children <18 years of age in the ICU/SDU with acute COVID-19 at 48 pediatric hospitals in the United States were identified. Demographics, laboratory values, and clinical course were compared in children who did and did not receive COVID-19-directed therapies. Trends in COVID-19-directed therapies over time were evaluated.

RESULTS

Of 424 children in the ICU/SDU, 235 (55%) received COVID-19-directed therapies. Children who received COVID-19-directed therapies were older than those who did not receive COVID-19-directed therapies (13.3 [5.6-16.2] vs 9.8 [0.65-15.9] years), more had underlying medical conditions (188 [80%] vs 104 [55%]; difference = 25% [95% CI: 16% to 34%]), more received respiratory support (206 [88%] vs 71 [38%]; difference = 50% [95% CI: 34% to 56%]), and more died (8 [3.4%] vs 0). Of the 235 children receiving COVID-19-directed therapies, 172 (73%) received systemic steroids and 150 (64%) received remdesivir, with rising remdesivir use over the study period (14% in March/April to 57% November/December).

CONCLUSION

Despite the lack of pediatric data evaluating treatments for COVID-19 in critically ill children, more than half of children requiring intensive or high acuity care received COVID-19-directed therapies.

Core concepts in pharmacoepidemiology: Confounding by indication and the role of active comparators

Confounding by indication poses a significant threat to the validity of nonexperimental studies assessing effectiveness and safety of medical interventions. While no different from other forms of confounding in theory, confounding by indication often requires specific methods to address the bias it creates in addition to common epidemiological adjustment or restriction methods. Clinical indication influencing treatment prescription is patient-specific and complex, making it challenging to measure within nonexperimental research. Restriction of the study population to patients with the indication for treatment would effectively mitigate confounding by indication and bring about comparability between exposure and comparator populations with respect to probability of the exposure. Active comparators are often an effective practical solution to restrict the study population in this manner when indication cannot be measured accurately. This article discusses various forms of confounding by indication, the utility of active comparators for nonexperimental studies of treatment effects, and the active comparator, new user (ACNU) study design to implicitly condition on indication. Considerations for selecting active comparators and conducting an ACNU study design are discussed to enable increased adoption of these methods, improve quality of nonexperimental studies, and ultimately strengthen our evidence base for intended and unintended treatment effects in relevant target populations.

Opioids and Breast Cancer Recurrence: A Systematic Review

Breast cancer has the greatest epidemiological impact in women. Opioids represent the most prescribed analgesics, both in surgical time and in immediate postoperative period, as well as in chronic pain management as palliative care. We made a systematic review analyzing the literature's evidence about the safety of opioids in breast cancer treatment, focusing our attention on the link between opioid administration and increased relapses. The research has been conducted using the PubMed database. Preclinical studies, retrospective and prospective clinical studies, review articles and original articles were analyzed. In the literature, there are several preclinical in vitro and in vivo studies, suggesting a possible linkage between opioids administration and progression of cancer disease. Nevertheless, these results are not confirmed by clinical studies. The most recent evidence reassures the safety of opioids during surgical time as analgesic associated with anesthetics drugs, during postoperative period for optimal cancer-related pain management and in chronic use. Currently, there is controversial evidence suggesting a possible impact of opioids on breast cancer progression, but to date, it remains an unresolved issue. Although there is no conclusive evidence, we hope to arouse interest in the scientific community to always ensure the best standards of care for these patients.

Association between proton pump inhibitors use and risk of hip fracture: A general population-based cohort study

Previous studies comparing risk of fracture among Proton Pump Inhibitors (PPIs) users with that among non-users were susceptible to confounding by indication. Epidemiologic studies of this association using an active medication as a comparator would appropriately address this bias. We conducted a propensity-score matched cohort study to compare the risk of incident fracture over five years among initiators of PPIs with initiators of histamine 2 receptor antagonist (H2RA) using data collected from The Health Improvement Network (THIN) database in the United Kingdom (2000-2016). The prevalence of PPIs prescription increased 3.8-fold from 2000 (7.9%) to 2012 (30.3%) and remained stable since then. Of the 50,265 propensity-score matched participants in each cohort (mean age was 65 years, and 57% were women), 370 (1.9/1000 person-years) incident hip fracture occurred in the PPIs initiators and 294 (1.5/1000 person-years) in the H2RA initiators during the follow-up period. The rate difference of incident hip fracture for PPIs initiation was 0.4 (95% confidence interval [CI]: 0.2-0.7)/1000 person-years compared with H2RA initiation and the corresponding hazard ratio (HR) was 1.27 (95%CI: 1.09-1.48). Compared with non-PPI use, multivariable-adjusted odds ratios (ORs) of hip fracture were 1.17 (95%CI: 0.94-1.46), 1.55 (95%CI: 1.23-1.96), and 1.67 (95%CI: 1.33-2.10) for 1-2, 3-9 and ≥ 10 prescriptions of PPIs, respectively (P for trend = 0.001). We found that PPIs prescription has been increasing rapidly over the past decade in the United Kingdom, and the initiation of PPIs was associated with a higher risk of hip fracture than initiation of H2RA.

Risk of Major Adverse Cardiovascular Events Associated with Concomitant Use of Antidepressants and Non-steroidal Anti-inflammatory Drugs: A Retrospective Cohort Study

BACKGROUND

Both antidepressants and non-steroidal anti-inflammatory drugs (NSAIDs) have been reported to affect platelet aggregation, blood pressure and heart rate. Despite the high prevalence of the combined use of antidepressants and NSAIDs, there is limited evidence on the potential risk of major adverse cardiovascular events (MACE) associated with their use.

OBJECTIVE

The objective of this study was to assess the association between concomitant antidepressant and NSAID use and MACE.

METHODS

We conducted a retrospective cohort study using South Korea's nationwide healthcare database. The study cohort was defined as those with new prescriptions for antidepressants and NSAIDs between 2004 and 2015. Exposure was assessed as time varying into four discrete periods: non-use, antidepressant use, NSAID use and concomitant use. Our primary outcome was MACE, a composite of haemorrhagic and thromboembolic events; secondary outcomes were the individual events of MACE. A multivariable Cox proportional hazards model was used to estimate hazards ratios with 95% confidence intervals. We also performed subgroup analyses by class of antidepressant/type of NSAIDs, age and sex.

RESULTS

From 240,982 patients, 235,080, 4393 and 1509 patients were users of NSAIDs, antidepressants or both drugs at cohort entry, respectively. The cohort generated 2.1 million person-years of follow-up with 22,453 events of MACE (incidence rate 1.07 per 100 person-years). Compared with non-use, concomitant use (hazard ratio 1.13, 95% confidence interval 1.01-1.26) and NSAID-only use (1.05, 1.001-1.10) were positively associated with MACE, while antidepressant-only use showed a negative association (0.91, 0.83-0.99). Concomitant use increased the individual risk of haemorrhagic stroke (1.46, 1.06-2.00), ischaemic stroke (1.22, 1.07-1.38) and heart failure (1.19, 1.02-1.38), but showed a protective effect on cardiovascular deaths (0.36, 0.21-0.62). Of the six possible combinations of antidepressants and NSAIDs by their classes, only concomitant use of tricyclic antidepressants and non-selective NSAIDs was positively associated with MACE (1.26, 1.09-1.47). The risk of MACE remained elevated with concomitant use among those aged ≥ 45 years (1.14, 1.01-1.29) and male patients (1.19, 1.01-1.42).

CONCLUSIONS

Concomitant use of antidepressants and NSAIDs moderately elevated the risk of MACE, of which the observed risk appears to be driven by the concomitant use of tricyclic antidepressants and non-selective NSAIDs. Thus, healthcare providers should take precaution when co-prescribing these drugs, weighing the potential benefits and risks associated with their use.

Real-world evidence: the devil is in the detail

Much has been written about real-world evidence (RWE), a concept that offers an understanding of the effects of healthcare interventions using routine clinical data. The reflection of diverse real-world practices is a double-edged sword that makes RWE attractive but also opens doors to several biases that need to be minimised both in the design and analytical phases of non-experimental studies. Additionally, it is critical to ensure that researchers who conduct these studies possess adequate methodological expertise and ability to accurately implement these methods. Critical design elements to be considered should include a clearly defined research question using a causal inference framework, choice of a fit-for-purpose data source, inclusion of new users of a treatment with comparators that are as similar as possible to that group, accurately classifying person-time and deciding censoring approaches. Having taken measures to minimise bias 'by design', the next step is to implement appropriate analytical techniques (for example propensity scores) to minimise the remnant potential biases. A clear protocol should be provided at the beginning of the study and a report of the results after, including caveats to consider. We also point the readers to readings on some novel analytical methods as well as newer areas of application of RWE. While there is no one-size-fits-all solution to evaluating RWE studies, we have focused our discussion on key methods and issues commonly encountered in comparative observational cohort studies with the hope that readers are better equipped to evaluate non-experimental studies that they encounter in the future. Graphical abstract.

Methodological considerations when analysing and interpreting real-world data

In the absence of relevant data from randomized trials, nonexperimental studies are needed to estimate treatment effects on clinically meaningful outcomes. State-of-the-art study design is imperative for minimizing the potential for bias when using large healthcare databases (e.g. claims data, electronic health records, and product/disease registries). Critical design elements include new-users (begin follow-up at treatment initiation) reflecting hypothetical interventions and clear timelines, active-comparators (comparing treatment alternatives for the same indication), and consideration of induction and latent periods. Propensity scores can be used to balance measured covariates between treatment regimens and thus control for measured confounding. Immortal-time bias can be avoided by defining initiation of therapy and follow-up consistently between treatment groups. The aim of this manuscript is to provide a non-technical overview of study design issues and solutions and to highlight the importance of study design to minimize bias in nonexperimental studies using real-world data.

Budesonide/formoterol therapy: effective and appropriate use in asthma and chronic obstructive pulmonary disease

Aim: Quality, real-world comparative effectiveness (CE) studies of asthma and chronic obstructive pulmonary disease therapy efficacy are scarce. We identified and evaluated peer-reviewed CE and appropriate-use evaluations of budesonide/formoterol combination (BFC) maintenance therapy. Materials & methods: Analyses were limited to retrospective, real-world utilization studies of BFC delivered by pressurized metered-dose inhalers. Results: In a CE study of BFC versus fluticasone/salmeterol combinations (FSC) in asthma, BFC users had fewer total exacerbations. In appropriate-use studies of asthma treatment, BFC patients were consistently more likely to meet treatment escalation recommendations. BFC comparisons with FSC or tiotropium for chronic obstructive pulmonary disease found differences in exacerbation rates and rescue inhaler use. Conclusion: We found available, good quality BFC CE and appropriate-use articles; however, all had limitations.

A systematic review of observational studies of the association between pioglitazone use and bladder cancer

AIM

To conduct a systematic review of all observational studies on the effect of pioglitazone on the risk of bladder cancer.

METHODS

The MEDLINE and EMBASE databases were queried for papers published between 1 January 2000 and 30 October 2017. We took into consideration observational studies (both retrospective and prospective) that included participants with Type 2 diabetes prescribed anti-hyperglycaemic drugs.

RESULTS

While some studies reported an association, others did not, and meta-analyses of these studies showed a significantly increased risk; however, while meta-analysis is a powerful and practical statistical tool, its results should be considered with caution when applied to widely heterogeneous studies. We describe how many of these studies are affected by different types of bias, most notably time-related biases, which should preclude a pooled analysis that would result in biased estimation of the risk.

CONCLUSIONS

Given existing data, it is not appropriate to pool the outcomes of highly heterogeneous studies and further rigorously conducted observational research is needed to clarify the role of pioglitazone use on the incidence of bladder cancer.

Description of an incidence-based model for Assessing comorbidity patterns in disease natural history

BACKGROUND

Patients with a chronic disease often suffer from other diseases called comorbidities, which can be important factors in the assessment of risks associated with the disease and its management. However, comorbidities can pose important methodological issues because factors such as time, age, duration and the disease can influence their impact on the risk of interest.

METHODS

To identify comorbidities of a chronic disease, it is common practice to construct 2 separate cohorts of patients-a set with the disease and another as a random sample of patients free of the disease-and compare the event rates for each candidate's comorbidity over a specific period between the 2, while accounting for factors which may confound the results. We describe an incidence-based alternative approach that exploits the longitudinal properties of observational databases to track incident event rates along the natural history of the chronic disease. We illustrate it in a retrospective cohort of patients with chronic obstructive pulmonary disease (COPD) aged 50 and above-each patient with COPD was matched with another without COPD on certain confounding factors.

RESULTS

We obtained 24 079 matched pairs. We found that chronic conditions such as lung cancer, asthma, fracture and osteoporosis were more common in patients with COPD. We also found evidence of time-varying associations.

CONCLUSIONS

Our findings in COPD suggest that time is an important factor and comorbidity studies which are based on information in a single fixed period (such as first year postdiagnosis of COPD) are more likely to report spurious associations.

Confounding by drug formulary restriction in pharmacoepidemiologic research

PURPOSE

The potential consequences of confounding due to drug formulary restrictions in pharmacoepidemiologic research remain incompletely understood. Our objective was to illustrate this potential bias using the example of fluticasone/salmeterol combination therapy, an oral inhaler used to treat asthma and chronic obstructive pulmonary disease, whose use is restricted in the province of Quebec, Canada.

METHODS

We identified all new users of fluticasone/salmeterol in Quebec's administrative databases and classified those who received their initial dispensing of fluticasone/salmeterol between 1 September 1999 and 30 September 2003 as users from the liberal period and those who received it between 1 January 2004 and 31 October 2006 as users from the restricted period. The primary outcome was time to first hospitalization for respiratory causes within 12 months of cohort entry.

RESULTS

Our cohort included 72 154 new users from the liberal period and 5058 from the restricted period. Compared with use during the liberal period, use during the restricted period was associated with an increased rate of hospitalization for respiratory causes (crude hazard ratio [HR] = 1.41, 95% confidence interval [CI] = 1.32, 1.51). Subsequent adjustment for age, sex, and hospitalization for respiratory causes in the previous year attenuated the association (HR = 1.05, 95%CI = 0.98, 1.12). Further adjustment for other potential confounders resulted in a lower rate during the restricted period (HR = 0.78, 95%CI = 0.73, 0.83).

CONCLUSIONS

Formulary restrictions can result in substantial and unexpected confounding and should be considered during the design and analysis of pharmacoepidemiologic studies.

Opioids and breast cancer recurrence: A Danish population-based cohort study

BACKGROUND

Opioids may alter immune function, thereby potentially affecting cancer recurrence. The authors investigated the association between postdiagnosis opioid use and breast cancer recurrence.

METHODS

Patients with incident, early stage breast cancer who were diagnosed during 1996 through 2008 in Denmark were identified from the Danish Breast Cancer Cooperative Group Registry. Opioid prescriptions were ascertained from the Danish National Prescription Registry. Follow-up began on the date of primary surgery for breast cancer and continued until breast cancer recurrence, death, emigration, 10 years, or July 31, 2013, whichever occurred first. Cox regression models were used to compute hazard ratios and 95% confidence intervals associating breast cancer recurrence with opioid prescription use overall and by opioid type and strength, immunosuppressive effect, chronic use (≥6 months of continuous exposure), and cumulative morphine-equivalent dose, adjusting for confounders.

RESULTS

In total, 34,188 patients were identified who, together, contributed 283,666 person-years of follow-up. There was no association between ever-use of opioids and breast cancer recurrence (crude hazard ratio, 0.98; 95% confidence interval, 0.90-1.1; adjusted hazard ratio, 1.0; 95% confidence interval, 0.92-1.1), regardless of opioid type, strength, chronicity of use, or cumulative dose. Breast cancer recurrence rates were lower among users of strongly (but not weakly) immunosuppressive opioids, possibly because of channeling bias among those with a high competing risk, because mortality was higher among users of this drug type.

CONCLUSIONS

This large, prospective cohort study provided no clinically relevant evidence of an association between opioid prescriptions and breast cancer recurrence. The current findings are important to cancer survivorship, because opioids are frequently used to manage pain associated with comorbid conditions.

Randomized Controlled Trials and real life studies. Approaches and methodologies: a clinical point of view

Randomized Controlled Trials (RCTs) are the "gold standard" for evaluating treatment outcomes providing information on treatments "efficacy". They are designed to test a therapeutic hypothesis under optimal setting in the absence of confounding factors. For this reason they have high internal validity. The strict and controlled conditions in which they are conducted, leads to low generalizability because they are performed in conditions very different from real life usual care. Conversely, real life studies inform on the "effectiveness" of a treatment, that is, the measure of the extent to which an intervention does what is intended to do in routine circumstances. At variance to RCTs, real life trials have high generalizability, but low internal validity. Recently the number of real life studies has been rapidly growing in different areas of respiratory medicine, particularly in asthma and COPD. The role of such studies is becoming a hot topic in respiratory medicine, attracting research interest and debate. In the first part of this review we discuss some of the advantages and disadvantages of different types of RCTs and analyze the strengths and weaknesses of real life trials, considering the recent examples of some studies conducted in COPD. We then discuss methodological approaches and options to overcome some of the limitations of real life studies. Comparing the conclusions of effectiveness and efficacy trials can provide important pieces of information. Indeed, these approaches can result complementary, and they can guide the interpretation of each other results.

The exposure-crossover design is a new method for studying sustained changes in recurrent events

OBJECTIVES

To introduce a new design that explores how an acute exposure might lead to a sustained change in the risk of a recurrent outcome.

STUDY DESIGN AND SETTING

The exposure-crossover design uses self-matching to control within-person confounding due to genetics, personality, and all other stable patient characteristics. The design is demonstrated using population-based individual-level health data from Ontario, Canada, for three separate medical conditions (n > 100,000 for each) related to the risk of a motor vehicle crash (total outcomes, >2,000 for each).

RESULTS

The exposure-crossover design yields numerical risk estimates during the baseline interval before an intervention, the induction interval immediately ahead of the intervention, and the subsequent interval after the intervention. Accompanying graphs summarize results, provide an intuitive display to readers, and show risk comparisons (absolute and relative). Self-matching increases statistical efficiency, reduces selection bias, and yields quantitative analyses. The design has potential limitations related to confounding, artifacts, pragmatics, survivor bias, statistical models, potential misunderstandings, and serendipity.

CONCLUSION

The exposure-crossover design may help in exploring selected questions in epidemiology science.

Measuring exacerbations in obstructive lung disease

PURPOSE

Using hospitalization always has been seen as a solid measurement for exacerbation in pharmacoepidemiology, but might lead to an underestimation of disease exacerbation because of a trend towards outpatient care. The aim of this study was to quantify the incidence of different exacerbation markers in obstructive lung disease and to identify predictors for these exacerbation markers.

METHODS

We conducted a cohort study using the PHARMO record linkage system, including demographic details and complete medication histories of more than two million community-dwelling residents in the Netherlands from 1985 onwards. Eligible patients were adult users of inhaled corticosteroids (ICS). Outcome parameters were hospitalization and short courses of systemic corticosteroids. Patients were allowed to have multiple exacerbations during follow-up.

RESULTS

We identified 5327 patients. During follow-up, 8635 exacerbations occurred in 2332 patients with a trend in time towards treating exacerbations out of the hospital (p-value 0.003). Of all patients with exacerbations, 73% was not hospitalized during follow-up. Exacerbations were associated with high-dose ICS use (adjusted RR 1.4; 95% CI 1.2-1.7) and chronic systemic corticosteroid use (adjusted RR 1.9; 95%CI 1.6-2.2).

CONCLUSIONS

Using hospitalization only as exacerbation marker leads to underestimating the exacerbation rate, because of exacerbation treatment out of the hospital. Patients with obstructive lung disease using chronic systemic corticosteroids or high-dose ICS use are more prone to exacerbations. This implies that these patients should be monitored carefully to prevent recurrent exacerbations which are detrimental for their prognosis and quality of life.

Bias-variance trade-off in pharmacoepidemiological studies using physician-preference-based instrumental variables: a simulation study

PURPOSE

Instrumental variables (IV) methodology removes bias due to unobserved confounding by replacing in the analysis the treatment with another variable--the instrument--that is well correlated with the treatment and independent of confounders. Recently, physician drug preference, operationalized as the treatment prescribed to the previous patient of the same physician, was proposed as an instrument in database studies comparing two competing drugs. We assessed, in simulations, how the performance of the IV estimates depends on the strength of this instrument.

METHODS

The 'physician preference' instrument correlates well with the treatment only if physician preferences affect the treatment received by a large fraction of patients. Yet, often there is a subgroup of patients whose treatment cannot be affected by physician's preferences. The larger this subgroup is, the weaker the instrument. We investigated the impact of weakening this instrument on the performance of IV estimates, by comparing risk difference estimates from the conventional and IV analyses in the presence of an unobserved confounder, for both continuous and binary outcomes.

RESULTS

The IV estimates were uniformly less biased than the conventional estimates, but had higher variance. Accordingly, the bias-variance trade-off favors the IV estimates only when physician' preference is a strong instrument. Still, the coverage rate of the 95%CI for the IV estimates was very close to the nominal 95%, while it was consistently lower for the conventional estimates.

CONCLUSION

Researchers should consider using the 'physician preference' instrument when comparing two competing drugs, but should be aware of the underlying assumptions.

Effects of corticosteroid use on readmission in obstructive lung disease

OBJECTIVE

Obstructive lung disease is a leading cause of morbidity and mortality worldwide. Some patients are readmitted, but currently predicting parameters for identifying these patients are lacking. The aim of this study was to quantify the incidence of readmission in chronic obstructive lung disease and to identify determinants for hospital readmission.

METHODS

We conducted a cohort study using the PHARMO record linkage system, including demographic details and complete medication histories of more than two million community-dwelling residents in the Netherlands from 1985 onwards. Eligible patients were adult users of inhaled corticosteroids (ICS) with an admission for obstructive lung disease. The outcome parameter was readmission within a follow-up period of one year.

RESULTS

We identified 605 ICS users with an admission for chronic obstructive lung disease, 132 of these patients were readmitted. Readmission was associated with a high Chronic Disease Score (adjusted HR 2.4; 95% CI 1.1-5.3). Patients using short courses of systemic corticosteroids only (adjusted HR 0.5; 95% CI 0.4-0.8) or combined with antibiotics (adjusted HR 0.4; 95% CI 0.2-0.6) were at decreased risk of readmission. The effect of high-dose ICS use varied over time.

CONCLUSIONS

Treatment of exacerbations out of the hospital was associated with a decreased risk of readmission, while patients with multiple chronic diseases are at increased risk of readmission for obstructive lung disease. These patients should be educated and should be invited to consultation more often to be able to detect exacerbation in an early phase and start treatment as early as possible.

Effect of date of drug marketing on disproportionality measures in pharmacovigilance: the example of suicide with SSRIs using data from the UK MHRA

BACKGROUND

Warnings concerning an increased risk of suicide in patients treated with selective serotonin reuptake inhibitors (SSRIs) re-emerged in early 2003, culminating in the broadcast of a television programme in the UK. In the following months, cumulated proportional reporting ratios showed that the most recently marketed drug, escitalopram, had a much higher proportion of reports of suicide to other adverse drug reactions (ADRs) than the other drugs in the class.

OBJECTIVE

To study the reporting patterns over time concerning suicide with the six SSRIs marketed in the UK as of March 2003 and their potential effect on disproportionality signal detection.

METHODS

Monthly cumulated numbers of reports were obtained from the UK Medicines and Healthcare products Regulatory Agency (MHRA), from the time of the first marketing of the drugs concerned and monthly for the 2 months prior to and the 9 months following the broadcast of the television programme (broadcast date: 11 May 2003), and the monthly ratio of suicide to other reports was computed for each SSRI individually and for all SSRIs combined.

RESULTS

Of the six SSRIs studied, five (citalopram, paroxetine, fluoxetine, sertraline and venlafaxine) had been marketed for several years and escitalopram for only a few months. At the end of the analysis period, 1.42% (4/281) of all ADR reports for escitalopram were of suicide versus 0.58% for the other five drugs combined (146/25 197). For all SSRIs combined, suicide represented 0.5% (123/24 315) of reports before the broadcast of the television programme, and increased to 2.3% (27/1163) following the programme. For escitalopram, suicide represented 1.1% (1/89) of all ADR reports before the television programme and 1.6% (3/192) afterwards. For the five other drugs combined, suicide represented 0.5% (122/24 226) of ADR reports before the television programme and 2.5% (24/971) afterwards (varying from 1.4% to 4.7% for the various drugs). The post-programme events represented 68% of all reports and 75% of suicides for escitalopram, whereas for older drugs they represented 3.6% of reports and 13% of suicides.

CONCLUSION

For older drugs, the events reported during the high-reporting post-television programme period were diluted by years of low reporting. For escitalopram, although the television programme had little absolute impact on the number of reports, because the drug had been on the market for such a short period of time, a large relative effect was observed. Differential effects related to time on market on cumulated reporting of adverse drug reactions should be taken into account when analysing spontaneous reporting databases with automated signal generation methods after an alert has changed the spontaneous reporting patterns. Proper use of measures of disproportionality requires thorough knowledge of potential biases and careful analysis of reporting patterns. We found no obvious differences between SSRIs once these were taken into account.

Impact of mis-specification of the treatment model on estimates from a marginal structural model

Inverse probability of treatment weighted (IPTW) estimation for marginal structural models (MSMs) requires the specification of a nuisance model describing the conditional relationship between treatment allocation and confounders. However, there is still limited information on the best strategy for building these treatment models in practice. We developed a series of simulations to systematically determine the effect of including different types of candidate variables in such models. We explored the performance of IPTW estimators across several scenarios of increasing complexity, including one designed to mimic the complexity typically seen in large pharmacoepidemiologic studies.Our results show that including pure predictors of treatment (i.e. not confounders) in treatment models can lead to estimators that are biased and highly variable, particularly in the context of small samples. The bias and mean-squared error of the MSM-based IPTW estimator increase as the complexity of the problem increases. The performance of the estimator is improved by either increasing the sample size or using only variables related to the outcome to develop the treatment model. Estimates of treatment effect based on the true model for the probability of treatment are asymptotically unbiased.We recommend including only pure risk factors and confounders in the treatment model when developing an IPTW-based MSM.

The case-crossover study design in pharmacoepidemiology

In the study of the association of transient drug exposures with acute outcomes, the case-crossover design is an efficient alternative to the case-control approach. This design based exclusively on the case series uses within-subject comparisons of drug exposures over time to estimate the rate ratio of the outcome associated with the drug under study. This design inherently removes the biasing effects of unmeasured, time-invariant confounding factors from the estimated rate ratio, but is sensitive to several assumptions. We illustrated the case-crossover design and explored its sensitivity using data from 4028 cases of gastrointestinal bleeding from the General Practice Research Database in assessing the effects of the drug warfarin. We compared the use of different time window lengths to assess exposure and considered the use of a case-time-control design to account for exposure time trends. The case-crossover approach found no excess risk of bleeding with warfarin exposure [rate ratio 0.98; 95% confidence interval (CI): 0.74-1.28] using a 1-month time window. When we restricted the analysis to subjects with truly transient drug exposure, defined by 1 to 3 prescriptions in the previous year, the rate ratio was 2.59 (95% CI: 1.42-4.74). To consider the longer 1-year exposure time window, the case-time-control approach was used and resulted in a rate ratio of 1.72 (95% CI: 1.08-2.43). In conclusion, the case-crossover design is potentially a powerful approach to assess the risk of drugs. This design is, however, highly sensitive to assumptions about intermittency of drug use and the length of the exposure time window, as demonstrated with the example of bleeding associated with warfarin use.

Three generations of ongoing controversies concerning the use of short acting beta-agonist therapy in asthma: a review

An increase in asthma mortality in 1960s noted by British authors stirred a debate about the use of beta-adrenergic therapy that has persisted in the medical literature. The cause appears to be isoproterenol and fenoterol overuse. A second debate evolved around the possible deleterious, pro-inflammatory effects, of the albuterol distomer. Most clinical studies showed improved bronchodilatation, but limited benefits from using levalbuterol. Recently, genotyping has uncovered a single nucleotide polymorphism at codon 16 that appears to affect the long term response to both regular and as needed use of albuterol, calling for a new genotype based therapeutic approach in asthma.

Antimicrobial drugs and community-acquired Clostridium difficile-associated disease, UK

In a population-based case-control study of community-acquired Clostridium difficile–associated disease (CDAD), we matched 1,233 cases to 12,330 controls. CDAD risk increased 3-fold with use of any antimicrobial agent and 6-fold with use of fluoroquinolones. Prior use of antimicrobial agent did not affect risk for CDAD after 6 months.

Early and late coronary stent thrombosis of sirolimus-eluting and paclitaxel-eluting stents in routine clinical practice: data from a large two-institutional cohort study

BACKGROUND

Stent thrombosis is a safety concern associated with use of drug-eluting stents. Little is known about occurrence of stent thrombosis more than 1 year after implantation of such stents.

METHODS

Between April, 2002, and Dec, 2005, 8146 patients underwent percutaneous coronary intervention with sirolimus-eluting stents (SES; n=3823) or paclitaxel-eluting stents (PES; n=4323) at two academic hospitals. We assessed data from this group to ascertain the incidence, time course, and correlates of stent thrombosis, and the differences between early (0-30 days) and late (>30 days) stent thrombosis and between SES and PES.

FINDINGS

Angiographically documented stent thrombosis occurred in 152 patients (incidence density 1.3 per 100 person-years; cumulative incidence at 3 years 2.9%). Early stent thrombosis was noted in 91 (60%) patients, and late stent thrombosis in 61 (40%) patients. Late stent thrombosis occurred steadily at a constant rate of 0.6% per year up to 3 years after stent implantation. Incidence of early stent thrombosis was similar for SES (1.1%) and PES (1.3%), but late stent thrombosis was more frequent with PES (1.8%) than with SES (1.4%; p=0.031). At the time of stent thrombosis, dual antiplatelet therapy was being taken by 87% (early) and 23% (late) of patients (p<0.0001). Independent predictors of overall stent thrombosis were acute coronary syndrome at presentation (hazard ratio 2.28, 95% CI 1.29-4.03) and diabetes (2.03, 1.07-3.83).

INTERPRETATION

Late stent thrombosis was encountered steadily with no evidence of diminution up to 3 years of follow-up. Early and late stent thrombosis were observed with SES and with PES. Acute coronary syndrome at presentation and diabetes were independent predictors of stent thrombosis.

Étude des reports de prescription : objectifs, méthodes et limites

Prescription switch is a phenomenon of major interest for most of current questions in pharmacoepidemiology and pharmacoeconomics. However, only a few drug utilization studies focus on prescription switch description and analysis. Prescription switch can be considered at two different levels: global (drug market changes) or individual (description of patient's treatments patterns). The objective of this article is to describe the different types of prescription switch studies, according to this distinction. Objectives, type of data needed, and limits of each type of prescription switch study are presented.

[Epidemiological studies in the HTA evaluation process]

Results of epidemiological studies should be considered as part of the available evidence when evaluating drug treatment benefits in health technology assessment (HTA). Pharmaco-epidemiological databases can provide a broader understanding of the effectiveness of drugs in populations that are frequently underrepresented in clinical trials. Such databases are also useful to investigate drug safety with regard to socio-demographic and medical care-related indicators and hereby contribute to an optimal and targeted pharmacological therapy. Using examples from pharmaco-epidemiological asthma studies, the present article discusses associated difficulties in interpreting database results against the background of various sources of bias and proposes possibilities for integrating observational data into the HTA evaluation process. Researchers are challenged to engage in considerable efforts to develop a standardized inventory of epidemiological methods, e.g. for the pooled analysis of epidemiological data.

Economic evaluation of treating chronic obstructive pulmonary disease with inhaled corticosteroids and long-acting beta2-agonists in a health maintenance organization

OBJECTIVES

In light of recent results from observational studies showing prolonged survival in subjects taking long-acting beta2-agonists (LABA) and/or inhaled corticosteroids (ICS) for chronic obstructive pulmonary disease (COPD), we investigated their cost-effectiveness (CE).

METHODS

Costs and survival data were collected for a sample of members enrolled in a large Health Maintenance Organization in the United States. An observational study design was used to evaluate cumulative costs and health benefits of LABA, ICS, ICS+LABA, or comparison drugs. Survival was estimated using a parametric regression model. Costs were adjusted for censoring and prognostic factors. CE was evaluated over a time horizon of 36 months and the remaining lifetime of subjects.

RESULTS

Over 36 months, life expectancy and costs were: 2.4 years (95% confidence interval (CI): 2.3; 2.5) and $28,030 (CI: $23,400; $33,570) for not receiving ICS or LABA; 2.6 years (CI: 2.6; 2.7) and $35,170 (CI: $29,970; $40,620) for ICS alone; 2.6 years (CI: 2.5; 2.7) and $27,380 (CI: $21,780; $32,510) for LABA alone; and, 2.7 years (CI: 2.6; 2.8) and $33,780 (CI: $28,700; $39,440) for subjects treated with ICS+LABA. The lifetime analysis showed similar trends.

CONCLUSIONS

There is an acute need to find effective, life-extending treatments for persons with COPD. ICS, LABA or their combination represent promising treatment options and are currently being tested in randomized trials. If the impact on survival seen in these trials compares to that seen in observational studies, LABA and the combination treatment are likely to be cost-effective in the United States.

Overcoming gaps in the management of asthma in older patients: new insights

Asthma is under-recognised and undertreated in older populations. This is not surprising, given that one-third of older people experience significant breathlessness. The differential diagnosis commonly includes asthma, chronic obstructive pulmonary disease (COPD), heart failure, malignancy, aspiration and infections. Because symptoms and signs of several cardiorespiratory diseases are nonspecific in older people and diseases commonly co-exist, investigations are important. A simple strategy for the investigation of breathlessness in older people should include a full blood count, chest radiograph, ECG, peak flow diary and/or spirometry with reversibility as a minimum. If there are major abnormalities on the ECG, an echocardiogram should also be performed. Diurnal variability in peak flow readings >or=20% or >or=15% reversibility in forced expiratory volume in 1 second, spontaneously or with treatment, support a diagnosis of asthma. Distinguishing asthma from COPD is important to allow appropriate management of disease based on aetiology, accurate prediction of treatment response, correct prognosis and appropriate management of the chest condition and co-morbidities. The two conditions are usually readily differentiated by clinical features, particularly age at onset, variability of symptoms and nocturnal symptoms in asthma, supported by the results of reversibility testing. Full lung function tests may not necessarily help in differentiating the two entities, although gas transfer factor is characteristically reduced in COPD and usually normal or high in asthma. Methacholine challenge tests previously mainly used in research are now also used widely and safely to confirm asthma in clinical settings. Interest in exhaled nitric oxide as a biomarker of airways inflammation is increasing as a noninvasive tool in the diagnosis and monitoring of asthma. Regular inhaled corticosteroids (ICS) are the mainstay of treatment of asthma. Even in mild disease in older adults, regular preventive treatment should be considered, given the poor perception of bronchoconstriction by older asthmatic patients. If symptoms persist despite ICS, addition of long-acting beta(2)-adrenoceptor agonists (LABA) should be considered. Addition of LABA to ICS improves asthma control and allows reduction in ICS dose. However, older people have been grossly under-represented in trials of LABA, many trials having excluded those >or=65 years of age. On meta-analysis, beta(2)-adrenoceptor agonists (both short acting and long acting) are associated with increased cardiovascular mortality and morbidity in asthma and COPD. While the evidence for excess cardiovascular mortality is stronger for short-acting beta(2)-adrenoceptor agonists, it would be prudent to exercise particular care in using beta(2)-adrenoceptor agonists (long acting and short acting) in those at risk of adverse cardiovascular outcomes, including older people. Regular review of cardiovascular status (and monitoring of serum potassium concentration) in patients taking beta(2)-adrenoceptor agonists is crucial. The response to LABA should be carefully monitored and alternative 'add-on' therapy such as leukotriene receptor antagonists (LRA) should be considered. LRA have fewer adverse effects and in individual cases may be more effective and appropriate than LABA. Long-term trials evaluating beta(2)-adrenoceptor agonists and other bronchodilator strategies are needed particularly in the elderly and in patients with cardiovascular co-morbidities. There is no evidence that addition of anticholinergics improves control of asthma further, although the role of long-acting anticholinergics in the prevention of disease progression is currently being researched. Older patients need to be taught good inhaler technique to improve delivery of medications to lungs, minimise adverse effects and reduce the need for oral corticosteroids. Nurse-led education programmes that include a written asthma self-management plan have the potential to improve outcomes.

Prior pneumococcal vaccination is associated with reduced death, complications, and length of stay among hospitalized adults with community-acquired pneumonia

BACKGROUND

Vaccination with pneumococcal polysaccharide reduces the incidence of bacteremic pneumococcal disease in adults. We investigated the impact of prior pneumococcal vaccination on in-hospital mortality and the probability of respiratory failure among hospitalized adults with community-acquired pneumonia.

METHODS

Consecutive individuals hospitalized with community-acquired pneumonia (diagnosed by International Classification of Diseases, Ninth Revision, Clinical Modification codes 480.0-487.0) at 109 community and teaching hospitals in the United States were identified using the Quality and Resource Management System, a database constructed by Tenet HealthCare to improve the quality of patient care. Vaccination status, comorbidities, and outcomes were abstracted by case managers concurrently with patient care. Associations between vaccination, survival, and respiratory failure were defined using multivariable logistic regression models.

RESULTS

Of 62,918 adults hospitalized with community-acquired pneumonia between 1999 and 2003, 7390 (12%) had a record of prior pneumococcal vaccination. Vaccine recipients were less likely to die of any cause during hospitalization than were individuals with no record of vaccination (adjusted odds ratio [OR], 0.50; 95% confidence interval [CI], 0.43-0.59), even after adjustment for the presence of comorbid illnesses, age, smoking, and influenza vaccination and under varying assumptions about missing vaccination data. Vaccination also lowered the risk of respiratory failure (adjusted OR, 0.67; 95% CI, 0.59-0.76) and other complications and reduced median length of stay by 2 days, compared with nonvaccination (P<.001).

CONCLUSIONS

Prior vaccination against pneumococcus is associated with improved survival, decreased chance of respiratory failure or other complications, and decreased length of stay among hospitalized patients with community-acquired pneumonia. These observations reinforce current efforts to improve compliance with existing pneumococcal vaccination recommendations for adults.

Addressing the issue of channeling bias in observational studies with propensity scores analysis

Randomized Clinical Trials (RCTs) remain the gold standard for determining the utility of pharmaceuticals especially from a safety and efficacy standpoint. However, restrictive entry criteria and stringent protocols can be barriers to generalizing RCT findings to real world practices and outcomes. Observational studies overcome these limitations of RCTs since they are representative of real world populations and practices. Nonetheless, attributing causality remains a major limitation in observational studies, due to the non-random assignment of subjects to treatment. Non-random assignment can lead to imbalances in risk-factors between the groups being compared and thus bias the estimates of the treatment effect. Non-random assignment can be particularly problematic in observational studies comparing older versus newer pharmaceuticals from similar therapeutic classes due to the phenomenon of channeling. Channeling occurs when drug therapies with similar indications are preferentially prescribed to groups of patients with varying baseline prognoses. In this manuscript we discuss the phenomenon of channeling and the use of a statistical technique known an propensity scores analysis which potentially adjusts for the effects of channeling. During the course of this manuscript we discuss tests for determining the quality of the derived propensity score, various techniques for utilizing propensity scores, and also the potential limitations of this technique. With the increasing availability of high quality pharmaceutical and medical claims data for use in observational studies, increased attention must be given to analytic techniques that adjust optimally for non-random assignment and resulting channeling bias. For research studies using observational study designs, propensity score analysis offers a reasonable solution to address the limitation of non-random assignment, especially when RCTs are too costly, time-consuming or not ethically feasible.

Perspectives on the use of data mining in pharmaco-vigilance

In the last 5 years, regulatory agencies and drug monitoring centres have been developing computerised data-mining methods to better identify reporting relationships in spontaneous reporting databases that could signal possible adverse drug reactions. At present, there are no guidelines or standards for the use of these methods in routine pharmaco-vigilance. In 2003, a group of statisticians, pharmaco-epidemiologists and pharmaco-vigilance professionals from the pharmaceutical industry and the US FDA formed the Pharmaceutical Research and Manufacturers of America-FDA Collaborative Working Group on Safety Evaluation Tools to review best practices for the use of these methods.In this paper, we provide an overview of: (i) the statistical and operational attributes of several currently used methods and their strengths and limitations; (ii) information about the characteristics of various postmarketing safety databases with which these tools can be deployed; (iii) analytical considerations for using safety data-mining methods and interpreting the results; and (iv) points to consider in integration of safety data mining with traditional pharmaco-vigilance methods. Perspectives from both the FDA and the industry are provided. Data mining is a potentially useful adjunct to traditional pharmaco-vigilance methods. The results of data mining should be viewed as hypothesis generating and should be evaluated in the context of other relevant data. The availability of a publicly accessible global safety database, which is updated on a frequent basis, would further enhance detection and communication about safety issues.

The impact of allergy and pulmonary specialist care on emergency asthma utilization in a large managed care organization

OBJECTIVE

To evaluate the longitudinal impact of asthma specialist care on the risk of emergency department (ED) visits and hospitalization for asthma.

DATA SOURCES/STUDY SETTING

A prospective cohort study using both telephone survey and computerized utilization data.

STUDY DESIGN

We recruited a prospective cohort of 4,742 adult members of a closed panel managed care organization who were hospitalized for asthma (the "baseline hospitalization").

DATA COLLECTION/EXTRACTION METHODS

Visits to asthma specialists were ascertained from computerized utilization databases. Specialist visits after baseline hospitalization were defined as time-dependent covariates. An alternative analysis defined specialist visits during the year preceding baseline hospitalization. A subcohort of 596 subjects completed telephone interviews.

PRINCIPAL FINDINGS

Compared with subjects who received no specialist visits after baseline hospitalization, treatment by allergists (hazard ratio (HR) 1.04; 95 percent confidence interval (CI) 0.87-1.26) or pulmonologists (HR 0.92; 95 percent CI 0.71-1.19) was not associated with a reduction in the risk of future ED visits for asthma in the entire cohort, controlling for age, sex, race, recent asthma medication dispensing, and pharmacy benefits status. There was also no association between allergist visits and the risk of subsequent hospitalizations for asthma (HR 0.93; 95 percent CI 0.75-1.14). In contrast, visits to pulmonologists (HR 0.74; 95 percent CI 0.55-0.99) were related to a reduced risk of rehospitalization.

CONCLUSIONS

Pulmonary specialist visits appeared to reduce the risk of hospitalization for asthma, whereas asthma specialist visits did not reduce the risk of ED visits. In the context of comprehensive prepaid health care, the benefit of specialist care was modest.

Effectiveness of statins for secondary prevention in elderly patients after acute myocardial infarction: an evaluation of class effect

BACKGROUND

Clinical trials have shown the benefits of statins after acute myocardial infarction (AMI). However, it is unclear whether different statins exert a similar effect in reducing the incidence of recurrent AMI and death when used in clinical practice.

METHODS

We conducted a retrospective cohort study (1997-2002) to compare 5 statins using data from medical administrative databases in 3 provinces (Quebec, Ontario and British Columbia). We included patients aged 65 years and over who were discharged alive after their first AMI-related hospital stay and who began statin treatment within 90 days after discharge. The primary end point was the combined outcome of recurrent AMI or death from any cause. The secondary end point was death from any cause. Adjusted hazard ratios (HRs) for each statin compared with atorvastatin as the reference drug were estimated using Cox proportional hazards regression analysis.

RESULTS

A total of 18,637 patients were prescribed atorvastatin (n = 6420), pravastatin (n = 4480), simvastatin (n = 5518), lovastatin (n = 1736) or fluvastatin (n = 483). Users of different statins showed similar baseline characteristics and patterns of statin use. The adjusted HRs (and 95% confidence intervals) for the combined outcome of AMI or death showed that each statin had similar effects when compared with atorvastatin: pravastatin 1.00 (0.90-1.11), simvastatin 1.01 (0.91-1.12), lovastatin 1.09 (0.95-1.24) and fluvastatin 1.01 (0.80-1.27). The results did not change when death alone was the end point, nor did they change after adjustment for initial daily dose or after censoring of patients who switched or stopped the initial statin treatment.

INTERPRETATION

Our results suggest that, under current usage, statins are equally effective for secondary prevention in elderly patients after AMI.

Effectiveness of amoxicillin, azithromycin, cefprozil and clarithromycin in the treatment of acute otitis media in children: a population-based study

Population-based studies may give results different from randomized clinical trials assessing the efficacy of antibiotics.

OBJECTIVE

To determine the effectiveness of amoxicillin, azithromycin, cefprozil and clarithromycin in the treatment of acute otitis media (AOM) in children.

METHODS

Using Quebec Health Insurance databases (RAMQ), we selected a cohort of children aged < or = 6 years, with a first episode of AOM between 1999 and 2002. The index AOM was defined as a medical service claim with a diagnosis of AOM and an antibiotic dispensation in the following 72 hours. Failures were defined as a new antibiotic dispensation, a hospitalization or outpatient visit for complications related to AOM in the 30 days after the index AOM. Data were analyzed using logistic regression.

RESULTS

Overall, 12,693 failures occurred among 60,513 first episodes of AOM. Azithromycin was the only antibiotic that was associated with a decreased risk of failure overall, when compared to amoxicillin (OR 0.88, 95% CI: 0.82, 0.94). However in the first 3 days of treatment (n = 680), azithromycin was more associated with treatment failure (OR 1.6, 95% CI: 1.3, 2.0). Compared to amoxicillin, post-therapy failures (n = 9387) were more likely to occur with cefprozil (OR 1.2, 95%CI: 1.2, 1.3) but were less with azithromycin (OR 0.8 95% CI: 0.8, 0.9).

CONCLUSIONS

Azithromycin had the lowest risk of failure 30 days after the onset of treatment but an increased risk of failure during the first few days of treatment. Amoxicillin remains an effective first-line drug for treating first AOM episodes.

Bronchodilator treatment and deaths from asthma: case-control study

OBJECTIVE

To investigate the association between bronchodilator treatment and death from asthma.

DESIGN

Case-control study.

SETTING

33 health authorities or health boards in Great Britain.

PARTICIPANTS

532 patients under age 65 who died from asthma and 532 controls with a hospital admission for asthma matched for period, age, and area.

MAIN OUTCOME MEASURES

Odds ratios for deaths from asthma associated with prescription of bronchodilators and other treatment, with sensitivity analyses adjusting for age at onset, previous hospital admissions, associated chronic obstructive lung disease, and number of other drug categories.

RESULTS

After full adjustment, there were no significant associations with drugs prescribed in the 4-12 months before the index date. For prescriptions in the 1-5 years before, mortality was positively associated with inhaled short acting beta2 agonists (odds ratio 2.05, 95% confidence interval 1.26 to 3.33) and inversely associated with antibiotics (0.59, 0.39 to 0.89). The former association seemed to be confined to those aged 45-64, and the association with antibiotics was more pronounced in those under 45. Significant age interactions across all periods suggested inverse associations with oral steroids confined to the under 45 age group. An inverse association with long acting beta2 agonists and a positive association with methylxanthines in the 1-5 year period were non-significant.

CONCLUSION

There was no evidence of adverse effects on mortality with medium to long term use of inhaled long acting beta2 agonist drugs. The association with short acting beta(2) agonists has several explanations, only one of which may be a direct adverse effect.

Data collection, maintenance, and analysis for rheumatic disease research

With the increasing availability of inexpensive, powerful computers and software, clinicians and academics are constructing or thinking about constructing rheumatic disease outcomes databases. This article describes concepts, methods, and problems in database construction and analysis based on the experience of the US National Data Bank for Rheumatic Diseases.

Adverse effects of beta-agonists: are they clinically relevant?

Inhaled beta(2)-adrenoceptor agonists (beta(2)-agonists) are the most commonly used asthma medications in many Western countries. Minor adverse effects such as palpitations, tremor, headache and metabolic effects are predictable and dose related. Time series studies suggested an association between the relatively nonselective beta-agonist fenoterol and asthma deaths. Three case-control studies confirmed that among patients prescribed fenoterol, the risk of death was significantly elevated even after controlling for the severity of asthma. The Saskatchewan study not only found an increased risk of death among patients dispensed fenoterol, but also suggested this might be a class effect of beta(2)-agonists. However, in subsequent studies, the long-acting beta(2)-agonist salmeterol was not associated with increased asthma mortality. In a case-control study blood albuterol (salbutamol) concentrations were found to be 2.5 times higher among patients who died of asthma compared with controls. It is speculated that such toxic concentrations could cause tachyarrhythmias under conditions of hypoxia and hypokalemia. The risk of asthma exacerbations and near-fatal attacks may also be increased among patients dispensed fenoterol, but this association may be largely due to confounding by severity. Although salmeterol does not appear to increase the risk of near-fatal attacks, there is a consistent association with the use of nebulized beta(2)-agonists. Nebulized and oral beta(2)-agonists are also associated with an increased risk of cardiovascular death, ischemic heart disease and cardiac failure. Caution should be exercised when first prescribing a beta-agonist for patients with cardiovascular disease. A potential mechanism for adverse effects with regular use of beta(2)-agonists is tachyphylaxis. Tachyphylaxis to the bronchodilator effects of long-acting beta(2)-agonists can occur, but has been consistently demonstrated only for formoterol (eformoterol) a full agonist, rather than salmeterol, a partial agonist. Tachyphylaxis to protection against induced bronchospasm occurs with both full and partial beta(2)-agonists, and probably within a matter of days at most. Underlying airway responsiveness to directly acting bronchoconstricting agents is not increased when the bronchodilator effect of the regular beta(2)-agonist has been allowed to wear off, although there may be an increase in responsiveness to indirectly acting agents. While there has been speculation that underlying airway inflammation in asthma may be made worse by regular use of short-acting beta(2)-agonists, in contradistinction, a number of studies have shown that long-acting beta(2)-agonists have positive anti-inflammatory effects. An Australian Cochrane Airways Group systematic review of the randomized, controlled trials of short-acting beta-agonists found only minimal and clinically unimportant differences between regular use and use as needed. Regular short-acting treatment was better than placebo. However, a subsequent systematic review has found that regular use of long-acting beta-agonists had significant advantages over regular use of short-acting beta-agonists. More studies and data are needed on the regular use of beta(2)-agonists in patients not taking inhaled corticosteroids, and in potentially vulnerable groups, such as the elderly and those with particular genotypes for the beta-receptor, who might be more prone to adverse effects.

Asthma deaths; persistent and preventable mortality

Bronchial asthma remains a significant cause of mortality at all ages, despite the increased understanding of its pathogenesis and the range of drugs available for its treatment. Changes in therapeutic management can influence death rates and constant surveillance, combined with high-quality post mortem investigations, is essential. Disease severity, poor disease management and adverse psychosocial circumstances are all risk factors for asthma mortality. Bronchial asthma causes characteristic histological changes in the mucosa of the airways which are present even before the clinical diagnosis of asthma can be made. These include fibrous thickening of the lamina reticularis of the epithelial basement membrane, smooth muscle hypertrophy and hyperplasia, increased mucosal vascularity and an eosinophil-rich inflammatory cell infiltrate. In addition, mucoid plugging of the airway lumen is frequently associated with fatal asthma. The recognition of these changes can allow the diagnosis of asthma to be made for the first time at autopsy, in those cases where asthma goes undiagnosed in life. Acute severe asthma may be accompanied by pneumothorax and surgical emphysema of the mediastinum. Disorders which may mimic asthma include pulmonary embolism, chronic obstructive pulmonary disease and anaphylaxis, but careful post mortem examination and appropriate investigations should reveal the true cause of death.

Biases affecting the proportional reporting ratio (PPR) in spontaneous reports pharmacovigilance databases: the example of sertindole

BACKGROUND

Automated measures of reporting disproportionality in databases of spontaneous reports of adverse drug reactions are an emerging tool to identify drug-related alerts. Sertindole, a new atypical neuroleptic known to prolong the QT interval, was suspended in November 1998 because the proportion of reports of fatal reactions suggesting arrhythmia among all reports with sertindole was almost ten times higher than that for other atypical neuroleptics in the UK. This excess risk was not predicted in preclinical data and had not been found in premarketing trials.

METHOD

Reporting patterns over time were analysed. Prescription Event Monitoring (PEM) studies and a large retrospective cohort allowed for the comparison of actual death rates with atypical neuroleptics, and to assess which proportion of the deaths that occurred were reported.

RESULTS

There were indications of possible skewing of reporting related to notoriety, surveillance and market size effects. Death rates in PEM studies were essentially similar between sertindole and other neuroleptics. Cardiac deaths had been two to three times more often reported than other causes of death.

CONCLUSION

Proportional reporting ratios indicate differential reporting of possible reactions, not necessarily differential occurrence. There was no indication of an actual increase of risk of all causes or cardiac deaths during sertindole treatment, but only an increased risk of its being reported. The suspension of sertindole was rescinded by Committee on Proprietary Medicinal Products (CPMP) in October 2001.

Patterns of inhaled asthma medication use: a 3-year longitudinal analysis of prescription claims data from British Columbia, Canada

STUDY OBJECTIVES

To assess trends in asthma management and to identify factors associated with increasing short-acting (SA) beta-agonist utilization in British Columbia using administrative prescription data.

DESIGN

A retrospective cohort analysis.

SETTING

All patients between 13 and 50 years of age who had received at least one prescription for a SA beta-agonist covered by BC Pharmacare between January 1, 1996, and December 31, 1998.

METHODS

Cross-sectional analysis of all patients, and longitudinal analyses only of patients who had received at least one SA beta-agonist prescription in each of the 3 years. Trends in asthma medication use over time were evaluated using repeated-measures Mantel-Haenszel tests. Multiple logistic regression was used to identify factors associated with increasing SA beta-agonist use.

RESULTS

A total of 78,758 patients were included in the cohort. No decrease in the annual prevalence of receiving more than four canisters per year of a SA beta-agonist was identified between 1996 and 1998. A total of 12,844 patients filled at least one SA beta-agonist prescription each year. Time-trend analysis showed an overall increasing probability of not receiving an inhaled corticosteroid (ICS) agent in this population (p = 0.002). In patients exhibiting low SA beta-agonist use, > 18 years of age (adjusted odds ratio [OR], 1.5), male gender (adjusted OR, 1.7), and in receipt of social assistance (adjusted OR, 2.3) were associated with receiving increasing amounts of SA beta-agonist agents over the 3 years. In patients with a high degree of use of SA beta-agonists, only the receipt of social assistance (adjusted OR, 1.3) was significantly associated with increasing use.

CONCLUSIONS

Despite the development and dissemination of asthma management guidelines, there was no trend toward decreasing SA beta-agonist use. An unexpected trend toward decreasing ICS utilization was identified. Receiving social assistance was a risk factor for increasing SA beta-agonist use, independent of baseline utilization.

[Disagreement among hospital and community studies evaluating the same research question]

The goal of this review is to delineate some of reasons that justify the lack of consistency between hospital-based and community research. The main reasons for the differences are the selection of the hospital population and information based on clinical chart (its lack of uniformity and the treatment of the not available data). The reasons for lack of consistency are divided according to the type of research question: frequency, diagnosis, etiology, prognosis and treatment-prevention. The way a hospital population is selected justifies discrepancies regarding frequency and prognosis. As regards diagnosis, differences are mainly due the prevalence of disease. In the ascertainment of causality several biases are more common in hospital-based research, such as detection bias, protopathic (both producing an away-from-null estimate), and inclusion bias (diminishing the strength of association). Examples taken from the medical literature are offered to illustrate each bias. Regarding treatment-prevention problems arise from external validity, as clinical trials are less prone to bias; this latter situation is exemplified with an assessment of vaccine efficacy in both patients and healthy population. The frequency of citation of bias was assessed by a Medline search; in hospital studies detection bias and confounding by indication were more often quoted than in non-hospital research (RR = 2.71; 95% CI; 1.69-4.37; RR = 1.76; 95% CI, 0,90-3,42, respectively). Lastly, several recommendations are given to increase the validity of hospital-based research.