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- Performance of prior event rate ratio adjustment method in pharmacoepidemiology: a simulation study. [JOURNAL ARTICLE]
- Pharmacoepidemiol Drug Saf 2014 Nov 20.
Prior event rate ratio (PERR) adjustment method has been proposed to control for unmeasured confounding. We aimed to assess the performance of the PERR method in realistic pharmacoepidemiological settings.Simulation studies were performed with varying effects of prior events on the probability of subsequent exposure and post-events, incidence rates, effects of confounders, and rate of mortality/dropout. Exposure effects were estimated using conventional rate ratio (RR) and PERR adjustment method (i.e. ratio of RR post-exposure initiation and RR prior to initiation of exposure).In the presence of unmeasured confounding, both conventional and the PERR method may yield biased estimates, but PERR estimates appear generally less biased estimates than the conventional method. However, when prior events strongly influence the probability of subsequent exposure, the exposure effect from the PERR method was more biased than the conventional method. For instance, when the effect of prior events on the exposure was RR = 1.60, the effect estimate from the PERR method was RR = 1.13 and from the conventional method was RR = 2.48 (true exposure effect, RR = 2). In all settings, the variation of the estimates was larger for the PERR method than for the conventional method.The PERR adjustment method can be applied to reduce bias as a result of unmeasured confounding. However, only in particular situations, it can completely remove the bias as a result of unmeasured confounding. When applying this method, theoretical justification using available clinical knowledge for assumptions of the PERR method should be provided. Copyright © 2014 John Wiley & Sons, Ltd.
- Use of prescribed opioids by children and adolescents: Differences between Denmark, Norway and Sweden. [JOURNAL ARTICLE]
- Eur J Pain 2014 Nov 20.
There are few studies on the use of opioids among children and adolescents. The aim of this study was to determine the 1-year prevalence of prescribed opioid dispensing in Denmark, Norway and Sweden, and to compare gender and age differences in the use of weak and strong opioids between the three countries.Data on the dispensing of opioids were collected from the websites of the complete national prescription databases in the three countries. All individuals aged 0-19 with at least one prescription of opioids during the study period were included.The 1-year prevalence of opioid use among young individuals aged 0-19 years increased during the study period (2006-2012) in Denmark from 2.5 to 3.4 per thousand, in Norway from 10.7 to 13.4 per thousand and in Sweden from 5.9 to 7.1 per thousand. In all three countries, more boys than girls used opioids between the ages of 0 and 10, whereas girls were the major users in the age range 11-19. Use of opioids in all three countries was dominated by weak opioids, codeine being the most dominant in Norway and Sweden and tramadol in Denmark.The 1-year prevalence of prescribed opioid use among children and adolescents in Norway was far higher than in Denmark and Sweden. During the study period, an increasing use of opioids among children and adolescents was observed in all three countries.
- Linking mothers and infants within electronic health records: a comparison of deterministic and probabilistic algorithms. [JOURNAL ARTICLE]
- Pharmacoepidemiol Drug Saf 2014 Nov 18.
To compare probabilistic and deterministic algorithms for linking mothers and infants within electronic health records (EHRs) to support pregnancy outcomes research.The study population was women enrolled in Group Health (Washington State, USA) delivering a liveborn infant from 2001 through 2008 (N = 33 093 deliveries) and infant members born in these years. We linked women to infants by surname, address, and dates of birth and delivery using deterministic and probabilistic algorithms. In a subset previously linked using "gold standard" identifiers (N = 14 449), we assessed each approach's sensitivity and positive predictive value (PPV). For deliveries with no "gold standard" linkage (N = 18 644), we compared the algorithms' linkage proportions. We repeated our analyses in an independent test set of deliveries from 2009 through 2013. We reviewed medical records to validate a sample of pairs apparently linked by one algorithm but not the other (N = 51 or 1.4% of discordant pairs).In the 2001-2008 "gold standard" population, the probabilistic algorithm's sensitivity was 84.1% (95% CI, 83.5-84.7) and PPV 99.3% (99.1-99.4), while the deterministic algorithm had sensitivity 74.5% (73.8-75.2) and PPV 95.7% (95.4-96.0). In the test set, the probabilistic algorithm again had higher sensitivity and PPV. For deliveries in 2001-2008 with no "gold standard" linkage, the probabilistic algorithm found matched infants for 58.3% and the deterministic algorithm, 52.8%. On medical record review, 100% of linked pairs appeared valid.A probabilistic algorithm improved linkage proportion and accuracy compared to a deterministic algorithm. Better linkage methods can increase the value of EHRs for pregnancy outcomes research. Copyright © 2014 John Wiley & Sons, Ltd.
- Performance of time-dependent propensity scores: a pharmacoepidemiology case study. [JOURNAL ARTICLE]
- Pharmacoepidemiol Drug Saf 2014 Nov 18.
Pharmacoepidemiologic studies of acute effects of episodic exposures often must control for many time-dependent confounders. Marginal structural models permit this and provide unbiased estimates when confounders are on the causal pathway. However, if causal pathway confounding is minimal, analyses with time-dependent propensity scores, calculated for time periods defined by individual drug prescriptions, may have better efficiency. We justify time-dependent propensity scores and compare the performance of these methods in a case study from a previous investigation of the risk of medication toxicity death in current users of propoxyphene and hydrocodone, with both substantial time-dependent confounding and a large number of covariates.The cohort included Tennessee Medicaid enrollees who filled a qualifying study opioid prescription between 1992 and 2007. We identified 22 time-dependent covariates that accounted for most of the confounding in the original study. We compared analyses with all covariates in the regression model with those based on time-dependent propensity scores and those from marginal structural models.We identified 489,008 persons with 1,771,295 propoxyphene and 4,088,754 hydrocodone prescriptions. The unadjusted hazard ratio (propoxyphene : hydrocodone) was 0.70 (95%CI, 0.46-1.07). Estimates from inclusion of all covariates in the model, time-dependent propensity score analysis with inverse probability of treatment weighting, and marginal structural models were 1.63 (1.04-2.57), 1.65 (1.01-2.72), and 1.64 (0.83-3.27), respectively. Findings varied little with use of alternative propensity score methods, time origin, or techniques for marginal structural model estimation.Time-dependent propensity scores may be useful for pharmacoepidemiologic studies with time-varying exposures when causal pathway confounding is limited. Copyright © 2014 John Wiley & Sons, Ltd.
- Emergency contraceptive pill safety profile. Comparison of the results of a follow-up study to those coming from spontaneous reporting. [JOURNAL ARTICLE]
- Pharmacoepidemiol Drug Saf 2014 Nov 18.
The emergency contraceptive pill (ECP) containing levonorgestrel is dispensed without a prescription in Spain since 2009. An easy access could diminish unwanted pregnancies; however, there is a risk of misuse and, in any case, of developing some adverse events. The aim of the present study is to further learn the adverse effects of this ECP.An ad hoc follow-up study was carried out in three community pharmacies in a city of Central Spain; the sample was composed of those women asking for the ECP; they were interviewed by telephone after at least a month since the last menses. We completed the safety profile obtained with that coming from spontaneous reporting in Spain.Out of 139 women surveyed, 113 developed any adverse event-two considered as severe; the most frequently reported events were menstrual disturbances, which accounted for 21% of all events. Through spontaneous reporting, 36 cases of whatever adverse events related to levonorgestrel as ECP were identified. Twenty-five cases were considered as severe. Both types of reaction and severity were significantly different in the follow-up study and in the spontaneous reporting. Some of the reactions identified, such as miscarriage, febrile neutropenia, and porphyria, are not included in the Summary of Product Characteristics.Levonorgestrel as an ECP is mostly safe. Attention should be paid to some severe events and particularly to those risk factors for them to appear. Combining spontaneous reporting with an ad hoc follow-up study, the whole safety profile of a given medication can be obtained. Copyright © 2014 John Wiley & Sons, Ltd.
- In response. [Journal Article]
- Anesth Analg 2014 Dec; 119(6):1452.
- Hormone therapy after uterine cervical cancer treatment: a Swedish population-based study. [JOURNAL ARTICLE]
- Menopause 2014 Nov 17.
This study aims to assess use of hormone therapy (HT) after cervical cancer treatment in women of premenopause age.We identified 837 women aged 45 years or younger at diagnosis of cervical cancer in the Swedish Cancer Register from January 1, 2005 to September 30, 2009 with a minimal follow-up of 1.5 years. Information on cancer treatment (surgical operation, radiotherapy, and/or chemotherapy) was obtained through the National Patient Register. Use of HT was estimated through HT dispensing during follow-up as recorded in the Prescribed Drug Register. Percentage of recommended dose was assessed by frequency of HT dispensing at half-year intervals up to April 1, 2011 or a maximal age of 50 years.A total of 257 women (31%) received acute estrogen deprivation due to bilateral salpingo-oophorectomy and/or radiotherapy. Among these women, 171 (67%) of 257 had at least one dispensing of HT during the period 0.5 to 1 year after diagnosis, and 118 (46%) of 257 were dispensed 75% or more of the recommended dose. Proportion users decreased to 39% at 4.5 to 5 years after diagnosis (21% with ≥75% of the recommended dose). Women younger than 40 years had a higher prevalence of HT use at 0.5 to 1 year (79%), decreasing to 45% after 4.5 to 5 years. The results did not vary by cancer histology.Fewer than half of cervical cancer survivors with therapy-induced early menopause used HT at or close to the recommended dose, and the use decreased during follow-up. Increased awareness of the health benefits of HT for this patient group is needed among professionals and women.
- Opioid Abuse and Dependence during Pregnancy: Temporal Trends and Obstetrical Outcomes. [Journal Article]
- Anesthesiology 2014 Dec; 121(6):1158-65.
The authors investigated nationwide trends in opioid abuse or dependence during pregnancy and assessed the impact on maternal and obstetrical outcomes in the United States.Hospitalizations for delivery were extracted from the Nationwide Inpatient Sample from 1998 to 2011. Temporal trends were assessed and logistic regression was used to examine the associations between maternal opioid abuse or dependence and obstetrical outcomes adjusting for relevant confounders.The prevalence of opioid abuse or dependence during pregnancy increased from 0.17% (1998) to 0.39% (2011) for an increase of 127%. Deliveries associated with maternal opioid abuse or dependence compared with those without opioid abuse or dependence were associated with an increased odds of maternal death during hospitalization (adjusted odds ratio [aOR], 4.6; 95% CI, 1.8 to 12.1, crude incidence 0.03 vs. 0.006%), cardiac arrest (aOR, 3.6; 95% CI, 1.4 to 9.1; 0.04 vs. 0.01%), intrauterine growth restriction (aOR, 2.7; 95% CI, 2.4 to 2.9; 6.8 vs. 2.1%), placental abruption (aOR, 2.4; 95% CI, 2.1 to 2.6; 3.8 vs. 1.1%), length of stay more than 7 days (aOR, 2.2; 95% CI, 2.0 to 2.5; 3.0 vs. 1.2%), preterm labor (aOR, 2.1; 95% CI, 2.0 to 2.3; 17.3 vs. 7.4%), oligohydramnios (aOR, 1.7; 95% CI, 1.6 to 1.9; 4.5 vs. 2.8%), transfusion (aOR, 1.7; 95% CI, 1.5 to 1.9; 2.0 vs. 1.0%), stillbirth (aOR, 1.5; 95% CI, 1.3 to 1.8; 1.2 vs. 0.6%), premature rupture of membranes (aOR, 1.4; 95% CI, 1.3 to 1.6; 5.7 vs. 3.8%), and cesarean delivery (aOR, 1.2; 95% CI, 1.1 to 1.3; 36.3 vs. 33.1%).Opioid abuse or dependence during pregnancy is associated with considerable obstetrical morbidity and mortality, and its prevalence is dramatically increasing in the United States. Identifying preventive strategies and therapeutic interventions in pregnant women who abuse drugs are important priorities for clinicians and scientists.
- Higher mortality after myocardial infarction in patients with severe mental illness: a nationwide cohort study. [JOURNAL ARTICLE]
- J Intern Med 2014 Nov 17.
The aim of this study was to explore the impact of severe mental illness (SMI) on myocardial infarction survival, and determine the influence of risk factor burden, myocardial infarction severity and different treatments.This population-based cohort study, conducted in Sweden during the period 1997-2010, included all patients with a first diagnosis of myocardial infarction in the Swedish nationwide myocardial infarction register SWEDEHEART (n = 209 592). Exposure was defined as a diagnosis of SMI (i.e. bipolar disorder or schizophrenia) in the national patient register prior to infarction. Bias-minimized logistic regression models were identified using directed acyclic graphs and included as covariates age, gender, smoking, diabetes, previous cardiovascular disease, myocardial infarction characteristics and treatment.The primary outcomes were 30-day and 1-year mortality, obtained through linkage with national population registers.Patients with bipolar disorder (n = 442) and schizophrenia (n = 541) were younger (mean age 68 and 63 years, respectively) than those without SMI (n = 208 609; mean age 71 years). The overall 30-day and 1-year mortality rates were 10% and 18%, respectively. Compared with patients without SMI, patients with SMI had higher 30-day [odds ratio (OR) 1.99, 95% confidence interval (CI) 1.55-2.56] and 1-year mortality (OR 2.11, 95% CI 1.74-2.56) in the fully adjusted model. The highest mortality was observed among patients with schizophrenia (30-day mortality: OR 2.58, 95% CI 1.88-3.54; 1-year mortality: OR 2.55, 95% CI 1.98-3.29).SMI is associated with a marked higher mortality after myocardial infarction, even after accounting for contributing factors. It is imperative to identify the reasons for this higher mortality. This article is protected by copyright. All rights reserved.
- The use of natural language processing of infusion notes to identify outpatient infusions. [JOURNAL ARTICLE]
- Pharmacoepidemiol Drug Saf 2014 Nov 17.
Outpatient infusions are commonly missing in Veterans Health Affairs (VHA) pharmacy dispensing data sets. Currently, Healthcare Common Procedure Coding System (HCPCS) codes are used to identify outpatient infusions, but concerns exist if they correctly capture all infusions and infusion-related data such as dose and date of administration. We developed natural language processing (NLP) software to extract infusion information from medical text infusion notes. The objective was to compare the sensitivity of three approaches to identify infliximab administration dates and infusion doses against a reference standard established from the Veterans Affairs rheumatoid arthritis (VARA) registry.We compared the sensitivity and positive predictive value (PPV) of NLP to that of HCPCS codes in identifying the correct date and dose of infliximab infusions against a human extracted reference standard.The sensitivity was 0.606 (0.585-0.627) for HCPCS alone, 0.858 (0.842-0.873) for NLP alone, and 0.923 (0.911-0.934) for the two methods combined, with a PPV of 0.735 (0.716-0.754), 0.976 (0.969-0.983), and 0.957 (0.948-0.965) for each method, respectively. The mean dose of infliximab was 433 mg in the reference standard, 337 mg from HCPCS, 434 mg from NLP, and 426 mg from the combined method.HCPCS codes alone are not sufficient to accurately identify infliximab infusion dates and doses in the VHA system. The use of NLP significantly improved the sensitivity and PPV for estimating infusion dates and doses, especially when combined with HCPCS codes. Copyright © 2014 John Wiley & Sons, Ltd.