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Objective: To assess the variability in data distributions among data sources and over time through a case study of a large multisite repository as a systematic approach to data quality (DQ)., Materials and Methods: Novel probabilistic DQ control methods based on information theory and geometry are applied to the Public Health Mortality Registry of the Region of Valencia, Spain, with 512 143 entries from 2000 to 2012, disaggregated into 24 health departments. The methods provide DQ metrics and exploratory visualizations for (1) assessing the variability among multiple sources and (2) monitoring and exploring changes with time. The methods are suited to big data and multitype, multivariate, and multimodal data., Results: The repository was partitioned into 2 probabilistically separated temporal subgroups following a change in the Spanish National Death Certificate in 2009. Punctual temporal anomalies were noticed due to a punctual increment in the missing data, along with outlying and clustered health departments due to differences in populations or in practices., Discussion: Changes in protocols, differences in populations, biased practices, or other systematic DQ problems affected data variability. Even if semantic and integration aspects are addressed in data sharing infrastructures, probabilistic variability may still be present. Solutions include fixing or excluding data and analyzing different sites or time periods separately. A systematic approach to assessing temporal and multisite variability is proposed., Conclusion: Multisite and temporal variability in data distributions affects DQ, hindering data reuse, and an assessment of such variability should be a part of systematic DQ procedures., (© The Author 2016. Published by Oxford University Press on behalf of the American Medical Informatics Association. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Background: Patient registries (PRs) are important tools for public-health surveillance and rare-disease research. The purpose of this study is to identify the most important criteria for the creation of a rare-disease PR that could be used by public-health authorities to develop health policies., Methods: A consensus-development Delphi study was used, with participants selected for their expertize in rare diseases and registries. Participants were asked to complete a questionnaire on the most important criteria for creating PRs. Three rounds were performed., Results: Agreement was reached on half the questions in the first round and on 89% of questions in the final round, with a total expert participation rate of around 60% by the final stage. This study made it possible to reach a broader consensus starting from experts' initial assessment of the features that should be considered for the creation of a rare-disease PR., Conclusion: The consensus method used made it possible to define the characteristics of a PR based on expert opinion within a rare-disease framework. This study may serve as a guide for helping other researchers plan and build a rare-disease PR., (© The Author 2015. Published by Oxford University Press on behalf of Faculty of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: The aims of this European study were (i) to compare the level of renal function at the start of dialysis between age groups, gender, primary renal disease, comorbid conditions, treatment modality, time periods and countries, and (ii) to determine which baseline characteristics are associated with the level of renal function at the start of dialysis., Methods: Renal registries participating in the European Renal Association-European Dialysis and Transplant Association Registry provided data on serum creatinine 0-4 weeks before the start of dialysis in incident dialysis patients in 1999 and 2003. Data were available in 11 472 patients from nine renal registries. Glomerular filtration rate (GFR) was estimated by the four-variable Modification of Diet in Renal Disease equation., Results: The unadjusted median eGFR at the start of dialysis was 7.0 mL/min/1.73 m(2) in the 1999 data (median serum creatinine 7.5 mg/dL) and 7.7 mL/min/1.73 m(2) in the 2003 data (serum creatinine 7.0 mg/dL). Using linear regression with adjustment for the other covariates, older patients, males, patients with diabetes mellitus, hypertension/renal vascular disease (HT/RVD) as primary renal disease (vs glomerulonephritis), ischaemic heart disease or peripheral vascular disease and patients starting on peritoneal dialysis (PD) initiated dialysis at higher levels of eGFR (range Δ eGFR: 0.1-1.2 mL/min/1.73 m(2)). Using the same analyses, eGFR differed between countries (range: 6.5-8.6 mL/min/1.73 m(2))., Conclusions: During 2003, patients started dialysis at somewhat higher eGFR levels than those starting during 1999. There were also international differences in eGFR. Such differences may, at least in part, be explained by differences in creatinine measurement methods between countries and time periods. Finally, older patients, males, patients with HT/RVD or comorbidity and those starting on PD had slightly higher eGFR levels than younger patients, females, those with glomerulonephritis, without comorbidity and those starting on haemodialysis. Further research is needed into other, more clinically related factors affecting the decision to start dialysis.

Objective: To assess the quality of data on births in the Natural Population Movement (NPM) and congenital metabolic disorders registers with regard to calculation of reproductive and perinatal health indicators., Methods: The following comparisons between registers were made: (1) the total number of births to mothers living in Catalonia and Valencia from 2005 to 2006, (2) the percentage of missing data on the mother's geographical origin, (3) the percentage of missing data on the mother's age and the infant's birthweight and gestational age according to maternal origin., Results: The congenital metabolic disorders registers exhaustively collected the total number of births gathered in the NPM. The percentages of missing data on material origin and age were higher in the congenital metabolic disorders registers, although the proportion of births by maternal origin and the mean maternal age in each ethnic group was fairly similar to that in the NPM. The percentages of missing data on birthweight and gestational age were much higher in the NPM data than in the congenital metabolic disorders registers, especially among births registered in Catalonia and births to foreign mothers., Conclusions: Our results suggest some limitations in the quality of the data on gestational age and birthweight provided by NPM data, especially for comparisons of preterm and low birthweight indicators in the Spanish-born and immigrant populations. Moreover, the results point to the quality of the congenital metabolic disorders registers as a source to compare reproductive and perinatal health indicators., (Copyright (c) 2009 SESPAS. Published by Elsevier Espana. All rights reserved.)