Corinne S de Vries

The incidence of narcolepsy in Europe: Before, during, and after the influenza A(H1N1)pdm09 pandemic and vaccination campaigns

BACKGROUND In August 2010 reports of a possible association between exposure to AS03 adjuvanted pandemic A(H1N1)pdm09 vaccine and occurrence of narcolepsy in children and adolescents emerged in Sweden and Finland. In response to this signal, the background rates of narcolepsy in Europe were assessed to rapidly provide information for signal verification. METHODS We used a dynamic retrospective cohort study to assess the narcolepsy diagnosis rates during the period 2000-2010 using large linked automated health care databases in six countries: Denmark, Finland, Italy, the Netherlands, Sweden and the United Kingdom. RESULTS Overall, 2608 narcolepsy cases were identified in almost 280 million person years (PY) of follow up. The pooled incidence rate was 0.93 (95% CI: 0. 90-0.97) per 100,000 PY. There were peaks between 15 and 30 year of age (women>men) and around 60 years of age. In the age group 5-19 years olds rates were increased after the start of pandemic vaccination compared to the period before the start of campaigns, with rate ratios (RR) of 1.9 (95% CI: 1.1-3.1) in Denmark, 6.4 (95% CI: 4.2-9.7) in Finland and 7.5 (95% CI: 5.2-10.7) in Sweden. Cases verification in the Netherlands had a significant effect on the pattern of incidence over time. CONCLUSIONS The results of this incidence study provided useful information for signal verification on a population level. The safety signal of increased narcolepsy diagnoses following the start of the pandemic vaccination campaign as observed in Sweden and Finland could be observed with this approach. An increase in narcolepsy diagnoses was not observed in other countries, where vaccination coverage was low in the affected age group, or did not follow influenza A(H1N1)pdm09 vaccination. Patient level analyses in these countries are being conducted to verify the signal in more detail.

The incidence of primary glomerulonephritis worldwide: a systematic review of the literature

BACKGROUND Little is known about the worldwide variation in incidence of primary glomerulonephritis (GN). The objective of this review was to critically appraise studies of incidence published in 1980-2010 so that an overall view of trends of these diseases can be found. This would provide important information for determining changes in rates and understanding variations between countries. METHODS All relevant papers found through searches of Medline, Embase and ScienceDirect were critically appraised and an assessment was made of the reliability of the reported incidence data. RESULTS This review includes 40 studies of incidence of primary GN from Europe, North and South America, Canada, Australasia and the Middle East. Rates for the individual types of disease were found to be in adults, 0.2/100,000/year for membrano-proliferative GN, 0.2/100,000/year for mesangio-proliferative GN, 0.6/100,000/year for minimal change disease, 0.8/100,000/year for focal segmental glomerulosclerosis, 1.2/100,000/year for membranous nephropathy and 2.5/100,000/year for IgA nephropathy. Rates were lower in children at around 0.1/100,000/year with the exception of minimal change disease where incidence was reported to be 2.0/100,000/year in Caucasian children with higher rates in Arabian children (9.2/100,000/year) and Asian children (6.2-15.6/100,000/year). CONCLUSIONS This study found that incidence rates of primary GN vary between 0.2/100,000/year and 2.5/100,000/year. The incidence of IgA nephropathy is at least 2.5/100,000/year in adults; this disease can exist subclinically and is therefore only detected by chance in some patients. In addition, referral policies for diagnostic biopsy vary between countries. This will affect the incidence rates found.

The incidence of autoimmune thyroid disease: a systematic review of the literature

Objective  To undertake a systematic review of literature published between 1980 and 2008 on the incidence of autoimmune thyroid disease.

Smoking and delay to diagnosis are associated with poorer functional outcome in psoriatic arthritis

Objective To identify predictors of poorer physical function in established psoriatic arthritis (PsA). Methods PsA patients with disease duration of ≥10 years were identified from the Bath longitudinal cohort. Physical function was assessed using the Stanford Health Assessment Questionnaire (HAQ). Sex, age at diagnosis, duration of symptoms prior to diagnosis, smoking, treatment and year of diagnosis were included in a multivariable regression analysis to identify associations with HAQ. Results 267 patients were identified for inclusion. The median age was 56 years (IQR 45–63), median disease duration was 13 years (IQR 10–18) and median HAQ score was 0.63 (IQR 0.13–1.25). The model predicted significant increases in HAQ related to smoking (0.23, 95% CI 0.04 to 0.42), age >50 years at diagnosis (0.27, 95% CI 0.03 to 0.51), symptom duration of ≥1 year before diagnosis (0.22, 95% CI 0.02 to 0.42), female sex (0.39, 95% CI 0.20 to 0.57) and history of treatment with an anti-TNF agent (0.63, 95% CI 0.32 to 0.93) at follow-up. Conclusions Smoking, delay to diagnosis, older age at diagnosis, female sex and a history of anti-TNF treatment are associated with worse physical function in established PsA.

Data resources for investigating drug exposure during pregnancy and associated outcomes: The General Practice Research Database(GPRD) as an alternative to pregnancy registries

Pregnancy registries are the most commonly used data resource for the post-marketing surveillance of drug teratogenicity. However, the limited sample size and potential selection bias in these registries has led us to investigate the potential of the UK General Practice Research Database (GPRD) as an alternative data source for monitoring drug safety during pregnancy. In addition, a literature review identified further observational data sources that monitor pregnancy outcomes for future evaluation.Initial feasibility studies focused on the ability of the GPRD to capture pregnancy outcomes for a range of drug class exposures, all of which are currently under investigation in pregnancy registries, during pregnancy. The comparator pregnancy registries were identified via a MEDLINE search, whilst eligible pregnancies, in which women received one or more prescriptions for the drug of interest during pregnancy, were identified in the GPRD using the mother-baby link. The number of pregnancy outcomes following exposure to medication for arange of conditions with varying prevalence, including depression, migraine, epilepsy, herpes simplex and HIV, captured by the two data sources were compared. For depression, a relatively prevalent condition, the GPRD recorded the same number of mean annual intrauterine exposures to fluoxetine as the pregnancy registry (118 exposures/year). Ascertainment of intrauterine exposure to drug treatments for less prevalent conditions was found to be higher for the pregnancy registries than the GPRD; for the older antiepileptic drugs (valproate and carbamazepine), the pregnancy registry recorded between four and five times as many mean annual exposures as the GPRD. Virtually no antiretroviral exposures (three) were identified during the time period of interest on the GPRD, compared with 3946 in the Antiretroviral Pregnancy Registry.Data from the GPRD meet established criteria for evaluating outcomes of pregnancy. For prevalent conditions, it has the potential to replace or work alongside standard pregnancy registries and the alternative data sources identified. Further studies are now needed to assess its ability to replicate known teratogenic associations.

International collaboration to assess the risk of Guillain Barre Syndrome following Influenza A (H1N1) 2009 monovalent vaccines

BACKGROUND The global spread of the 2009 novel pandemic influenza A (H1N1) virus led to the accelerated production and distribution of monovalent 2009 Influenza A (H1N1) vaccines (pH1N1). This pandemic provided the opportunity to evaluate the risk of Guillain-Barré syndrome (GBS), which has been an influenza vaccine safety concern since the swine flu pandemic of 1976, using a common protocol among high and middle-income countries. The primary objective of this project was to demonstrate the feasibility and utility of global collaboration in the assessment of vaccine safety, including countries both with and without an established infrastructure for vaccine active safety surveillance. A second objective, included a priori, was to assess the risk of GBS following pH1N1 vaccination. METHODS The primary analysis used the self-controlled case series (SCCS) design to estimate the relative incidence (RI) of GBS in the 42 days following vaccination with pH1N1 vaccine in a pooled analysis across databases and in analysis using a meta-analytic approach. RESULTS We found a relative incidence of GBS of 2.42 (95% CI 1.58-3.72) in the 42 days following exposure to pH1N1 vaccine in analysis of pooled data and 2.09 (95% CI 1.28-3.42) using the meta-analytic approach. CONCLUSIONS This study demonstrates that international collaboration to evaluate serious outcomes using a common protocol is feasible. The significance and consistency of our findings support a conclusion of an association between 2009 H1N1 vaccination and GBS. Given the rarity of the event the relative incidence found does not provide evidence in contradiction to international recommendations for the continued use of influenza vaccines.

Healthcare databases in Europe for studying medicine use and safety during pregnancy

The aim of this study was to describe a number of electronic healthcare databases in Europe in terms of the population covered, the source of the data captured and the availability of data on key variables required for evaluating medicine use and medicine safety during pregnancy.

Evaluating the Hazard of Foetal Death following H1N1 Influenza Vaccination; A Population Based Cohort Study in the UK GPRD

Background To evaluate the risk of foetal loss associated with pandemic influenza vaccination in pregnancy. Retrospective cohort study. UK General Practice Research Database Pregnancies ending in delivery or spontaneous foetal death after 21 October 2009 and starting before 01 January 2010. Methodology/Principal Findings Hazard ratios of foetal death for vaccinated compared to unvaccinated pregnancies were estimated for gestational weeks 9 to 12, 13 to 24 and 25 to 43 using discrete-time survival analysis. Separate models were specified to evaluate whether the potential effect of vaccination on foetal loss might be transient (for ∼4 weeks post vaccination only) or more permanent (for the duration of the pregnancy). 39,863 pregnancies meeting our inclusion criteria contributed a total of 969,322 gestational weeks during the study period. 9,445 of the women were vaccinated before or during pregnancy. When the potential effect of vaccination was assumed to be transient, the hazard of foetal death during gestational weeks 9 through 12 (HRunadj 0.56; CI95 0.43 to 0.73) and 13 through 24 (HRunadj 0.45; CI95 0.28 to 0.73) was lower in the 4 weeks after vaccination than in other weeks. Where the more permanent exposure definition was specified, vaccinated pregnancies also had a lower hazard of foetal loss than unvaccinated pregnancies in gestational weeks 9 through 12 (HRunadj 0.74; CI95 0.62 to 0.88) and 13 through 24 (HRunadj 0.59; CI95 0.45 to 0.77). There was no difference in the hazard of foetal loss during weeks 25 to 43 in either model. Sensitivity analyses suggest the strong protective associations observed may be due in part to unmeasured confounding. Conclusions/Significance Influenza vaccination during pregnancy does not appear to increase the risk of foetal death. This study therefore supports the continued recommendation of influenza vaccination of pregnant women.

Identifying major congenital malformations in the UK general practice research database (GPRD): A study reporting on the sensitivity and added value of photocopied medical records and free text in the GPRD

AbstractBackground: Postmarketing teratogen surveillance is essential and requires a data source that can reliably capture a wide range of congenital malformations. The UK General Practice Research Database (GPRD) may have the potential to be used for this kind of surveillance. Objective: To assess the extent to which this database can be used to accurately identify major congenital malformations. Methods: This study was carried out as part of a broader study to compare data on anticonvulsant use and safety in pregnancy between the GPRD and a pregnancy registry. The study period ran from 1 January 1990 until 31 December 2006. Mother-baby pairs where the mother had a record of epilepsy, seizure or convulsion were identified using the GPRD computerized medical records. Infants of mother-baby pairs who had a record of a major congenital malformation were identified. Full photocopied paper medical records were requested from the infant’s general practitioner and where this was not possible any data entries consisting of uncoded comments, so-called ‘free text’, in the electronic GPRD record were requested from the database provider. This additional information was then reviewed in order to determine the extent to which the congenital malformation diagnoses identified via the computerized records could be confirmed or rejected and then classified as being major or minor. Results: Within the study population of 3869 live mother-baby pairs, 188 potentially major congenital malformations were identified from the GPRD computerized record relating to 161 unique individuals. Using a combination of photocopied medical records and free text it was possible to verify 160 malformations (85.1%) as the malformation indicated by the computerized records; this ranged from 91.7% of those cases verified using photocopied medical records and 77.9% of cases verified using free text. Of the verified congenital malformations, using a combination of computerized data, photocopied medical records and free text, it was possible to classify 78.1% as being major and 15.0% as minor, and this percentage was found to be the same for those cases reviewed by photocopied records and those where free text was used. The proportions of malformations that could be verified and those that could be classified as major or minor were found to vary by malformation class. Conclusions: The GPRD can be used to ascertain a wide range of congenital malformations. In many cases, when a malformation is identified in the GPRD via the computerized medical records, the malformation is likely to exist. However, in this study a small proportion of identified cases had to be excluded because they had been coded incorrectly or diagnostically ruled out. Therefore, depending on the congenital malformation of interest, verification of such malformations using photocopied medical records or free text is generally recommended.

Tibolone and endometrial cancer: a cohort and nested case-control study in the UK.

AbstractObjective: Case series and spontaneous reports of endometrial cancer have raised the question as to whether the use of tibolone (introduced into the UK in 1991) is associated with an increased risk of endometrial cancer. This study set out to evaluate whether tibolone use is associated with an increased risk of endometrial cancer. Methods: Age-adjusted incidence rate ratios (IRRs) of endometrial cancer were calculated for tibolone use compared with the use of other hormone replacement therapy (HRT). Separate sets of controls, matched for age and general practice, were compared with cases, all nested within a cohort of HRT users identified from the UK General Practice Research Database (GPRD). Conditional logistic regression analysis, adjusted for potential confounders, was used to study the association between tibolone use and the risk of endometrial cancer. Results: 4995 women used tibolone as their first HRT product; 10 783 (4.3%) of the users of combined HRT had changed to tibolone at some time during the study period. Amongst women whose HRT began with tibolone, the age-adjusted IRR relative to those who started with combined sequential HRT was 1.83 (95% CI 1.19, 2.82). The nested case-control study comprised 162 cases, each matched to two sets of 972 controls. There were 43 tibolone-exposed subjects, 28 of whom had used other HRT before or after tibolone. The adjusted odds ratio of the risk of endometrial cancer in women who had ever used tibolone, compared with users of combined sequential HRT, was 1.54 (95% CI 1.03, 2.32) in the age-matched set and 1.58 (95% CI 1.01, 2.47) in the practice-matched set. Sensitivity analyses did not decrease the risk estimates found. Discussion: Tibolone may be associated with an increased risk of endometrial cancer compared with conventional forms of HRT, but our data are fragile. Residual bias and uncontrolled confounding cannot be excluded, and follow-up time is insufficient to draw any firm conclusions with respect to the endometrial safety of tibolone.