Linking disease registries and nationwide healthcare administrative databases: the French renal epidemiology and information network (REIN) insight.

BACKGROUND: Record linkage is increasingly used in health research worldwide. Combining the patient information available in healthcare, administrative and clinical databases broadens the research perspectives, particularly for chronic diseases. Recent guidelines highlight the need for transparency on the used record linkage processes and the extracted data to be used by researchers. METHODS: Therefore, the aim of this study was to describe the deterministic iterative approach used to link the French Epidemiology and Information Network (REIN), a French national End-Stage Renal Disease registry, with the Système National des Données de Santé (SNDS), a French nationwide medico-administrative healthcare database. RESULTS: Among the 22,073 patients included in the REIN registry who started renal replacement therapy between 2014 and 2015 in France, 19,223 (87.1%) were matched with patients in the SNDS database. Comparison of matched and unmatched patients confirmed the absence of any major selection bias. Then, the record linkage was evaluated using the comorbidity status (diabetes). CONCLUSIONS: This fast and efficient method of record linkage with pseudonymized data and without unique and direct identifier might inspire other research teams. It also opens the path for new research on chronic kidney disease.

Sex-related differences in pre-dialysis trajectories and dialysis initiation: A French nationwide retrospective study.

BACKGROUND: In the last two decades, sex and gender differences have been documented in chronic kidney disease (CKD) management, including access to renal replacement therapy and its outcomes. The objectives of this study were to 1) compare the pre-dialysis healthcare utilization in men and women, and 2) examine the sex-specific factors associated with emergency dialysis start. METHODS: Adult patients with CKD who started dialysis in France in 2015 were extracted from the Renal Epidemiology and Information Network registry. Patients were matched to the French National Health Data System database to extract healthcare utilization data for the 2 years before dialysis start. Frequencies and monthly rates of consultations and hospitalizations were compared between men and women. Logistic regression analyses were performed separately in the two groups. RESULTS: Among the 8856 patients included, 3161 (35.7%) were women. Median age (71 years) and estimated glomerular filtration rate (8.1 and 7.7 ml/min for men and women) were similar between groups at dialysis start. Monthly consultations rates with a general practitioner and nephrology-related care were similar between women and men. Some sex-specific differences were found: higher frequencies of consultations with a psychiatrist in women and more frequent hospitalizations for circulatory system diseases in men. Emergency dialysis start rate was 30% in both groups. Emergency dialysis start was associated with acute nephropathy, compared with slowly progressive nephropathy, in women but not in men (OR = 1.48, p<0.01 vs 1.15, p = 0.18). CONCLUSIONS: This study found similar quantitative pre-dialysis healthcare utilization in men and women. To better understand sex/gender differences in CKD care trajectories, future research should focus on patients with CKD who are unknown to nephrology services, on patients receiving conservative care and on the sex/gender-specific mechanisms underlying care decision-making.

Prevalence of chronic kidney disease in France: methodological considerations and pitfalls with the use of Health claims databases.

Background: Health policy-making require careful assessment of chronic kidney disease (CKD) epidemiology to develop efficient and cost-effective care strategies. The aim of the present study was to use the RENALGO-EXPERT algorithm to estimate the global prevalence of CKD in France. Methods: An expert group developed the RENALGO-EXPERT algorithm based on healthcare consumption. This algorithm has been applied to the French National Health claims database (SNDS), where no biological test findings are available to estimate a national CKD prevalence for the years 2018-2021. The CONSTANCES cohort (+219 000 adults aged 18-69 with one CKD-EPI eGFR) was used to discuss the limit of using health claims data. Results: Between 2018 and 2021, the estimated prevalence in the SNDS increased from 8.1% to 10.5%. The RENALGO-EXPERT algorithm identified 4.5% of the volunteers in the CONSTANCES as CKD. The RENALGO-EXPERT algorithm had a positive predictive value of 6.2% and negative predictive value of 99.1% to detect an eGFR<60 ml/min/1.73 m². Half of 252 false positive cases (ALGO+, eGFR > 90) had been diagnosed with kidney disease during hospitalization, and the other half based on healthcare consumption suggestive of a 'high-risk' profile; 95% of the 1661 false negatives (ALGO-, eGFR < 60) had an eGFR between 45 and 60 ml/min, half had medication and two-thirds had biological exams possibly linked to CKD. Half of them had a hospital stay during the period but none had a diagnosis of kidney disease. Conclusions: Our result is in accordance with other estimations of CKD prevalence in the general population. Analysis of diverging cases (FP and FN) suggests using health claims data have inherent limitations. Such an algorithm can identify patients whose care pathway is close to the usual and specific CKD pathways. It does not identify patients who have not been diagnosed or whose care is inappropriate or at early stage with stable GFR.

REIN: a tool at the service of the patients / REIN : un outil au service des patients

On the occasion of the 20th anniversary of the REIN (French Renal Epidemiology and Information Network), a summary work on the contributions of the national French ESKD register was carried out. On the issue of patients' perspectives, the following key messages were retained. As shown by the SONG (Standardised Outcomes in Nephrology) initiative, the criteria for judging the dialysis treatment that patients and care-givers prefer are not those that are traditionally found in published studies. For example, for haemodialysis, they are fatigue, ability to travel, time without dialysis, impact on family and ability to work. The concern to give the patients a voice has been at the heart of the REIN registry right from the outset. In addition, there are patient representatives in the REIN Scientific Council and the Steering Group. Although mainly focused on quantitative health data collected from professionals, REIN has also supported studies pertaining to data collected directly from patients. These studies enable addressing questions pertaining to the problems faced by patients in their care pathway and their life with the disease. The setting up of a tool for routine and electronic collection of the patients' point of view in the evaluation of their treatment and the support of patient-initiated research contribute to positioning the REIN as a partner tool at the service of patients, unique in France.

À l'occasion des 20 ans du REIN (Réseau Épidémiologie et Information en Néphrologie), un travail de synthèse sur les apports du registre a été mené. Sur le point de vue des patients avec une maladie rénale stade 5, les messages clés suivants ont été retenus. L'initiative SONG (Standardised Outcomes in Nephrology) l'a montré, les critères de jugement de la prise en charge en dialyse que les patients et aidants privilégient ne sont pas ceux que l'on retrouve traditionnellement dans les études publiées. Par exemple, en hémodialyse, il s'agit de : la fatigue, la capacité à voyager, le temps sans dialyse, l'impact sur la famille et la capacité à travailler. La préoccupation de donner la parole aux patients a d'emblée été au coeur du registre REIN. En outre, des représentants de patients siègent au conseil scientifique REIN et au sein du groupe de pilotage. Bien qu'essentiellement orienté sur des données de santé quantitatives recueillies auprès des professionnels, REIN a également soutenu les études portant sur des données recueillies directement auprès des patients. Ces études permettent d'aborder des questions proches des problématiques des patients sur leurs parcours de soins et leur vie avec la maladie. La mise en place d'un outil de recueil électronique et de routine du point de vue des patients dans l'évaluation de leur prise en charge et le soutien de recherches à l'initiative des patients participent à positionner le REIN comme outil partenaire au service des patients, unique en France.

Care trajectory differences in women and men with end-stage renal disease after dialysis initiation.

Few studies investigated sex-related differences in care consumption after dialysis initiation. Therefore, the aim of this study was to compare the care trajectory in the first year after dialysis start between men and women by taking into account the context of dialysis initiation. All patients who started dialysis in France in 2015 were included. Clinical data of patients and context of dialysis initiation were extracted from the Renal Epidemiology and Information Network (REIN) registry. Data on care consumption in the first year after dialysis start came from the French national health data system (SNDS): hospital stays <24h, hospital stays to prepare or maintain vascular access, hospital stays >24h for kidney problems and hospital stays >24h for other problems, and consultations with a general practitioner. Variables were compared between men and women with the χ2 test and Student's or Welch t-test and logistic regression models were used to identify the factors associated with care consumption after dialysis start. The analysis concerned 8,856 patients (36% of women). Men were less likely to have a hospital stays >24h for kidney problems than women (OR = 0.8, 95% CI = [0.7-0.9]) and less general practitioner consultations (OR = 0.8, 95% CI = [0.8-0.9]), in the year after dialysis initiation, after adjustment on patient's characteristics. Moreover, hospital stays for vascular access preparation or maintenance were longer in women than men (median duration: 2 days [0-2] vs. 1 day [0-2], p < 0.001). In conclusion, despite greater comorbidities in men, this study found few differences in post-dialysis care trajectory between men and women.

Pre-dialysis care trajectory and post-dialysis survival and transplantation access in patients with end-stage kidney disease.

BACKGROUND: The pre-dialysis care trajectory impact on post-dialysis outcomes is poorly known. This study assessed survival, access to kidney transplant waiting list and to transplantation after dialysis initiation by taking into account the patients' pre-dialysis care consumption (inpatient and outpatient) and the conditions of dialysis start: initiation context (emergency or planned) and vascular access type (catheter or fistula). METHODS: Adults who started dialysis in France in 2015 were included. Clinical data came from the French REIN registry and data on the care trajectory from the French National Health Data system (SNDS). The Cox model was used to assess survival and access to kidney transplantation. RESULTS: We included 8856 patients with a mean age of 68 years. Survival was shorter in patients with emergency or planned dialysis initiation with a catheter compared to patients with planned dialysis with a fistula. The risk of death was lower in patients who were seen by a nephrologist more than once in the 6 months before dialysis than in those who were seen only once. The rate of kidney transplant at 1 year post-dialysis was lower for patients with emergency or planned dialysis initiation with a catheter (respectively, HR = 0.5 [0.4; 0.8] and HR = 0.7 [0.5; 0.9]) compared to patients with planned dialysis start with a fistula. Patients who were seen by a nephrologist more than three times between 0 and 6 months before dialysis start were more likely to access the waiting list 1 and 3 years after dialysis start (respectively, HR = 1.3 [1.1; 1.5] and HR = 1.2 [1.1; 1.4]). CONCLUSIONS: Nephrological follow-up in the year before dialysis initiation is associated with better survival and higher probability of access to kidney transplantation. These results emphasize the importance of early patient referral to nephrologists by general practitioners.

The dynamics of the general practitioner-nephrologist collaboration for the management of patients with chronic kidney disease before and after dialysis initiation: a mixed-methods study.

Background: Effective collaboration between general practitioners (GP) and nephrologists is crucial in CKD care. We aimed to analyse GPs' and nephrologists' presence and involvement in CKD care and assess how they intertwine to shape patients' trajectories. Methods: We conducted a mixed-methods study that included all patients with CKD who started dialysis in France in 2015 (the REIN registry) and a sample of nephrologists and GPs. We quantified professionals' presence through patients' reimbursed healthcare from the French National Health Data System, 2 years before and 1 year after dialysis start. Involvement in CKD care was derived from the nephrologists' and GPs' interviews. Results: Among 8856 patients included, nephrologists' presence progressively increased from 29% to 67% of patients with a contact during the 2 years before dialysis start. However, this was partly dependent on the GPs' referral practices. Interviews revealed that GPs initially controlled the therapeutic strategy on their own. Although unease grew with CKD's management complexity, reducing their involvement in favour of nephrologists, GPs' presence remained frequent throughout the pre-dialysis period. Upon dialysis start, nephrologists' presence and involvement became total, while GPs' greatly decreased (48% of patients with a contact at month 12 after dialysis start). Collaboration was smooth when GPs maintained contact with patients and could contribute to their care through aspects of their specialty they valued. Conclusions: This mixed-methods study shows presences and forms of involvement of GPs and nephrologists in CKD care adjusting along the course of CKD and unveils the mechanisms at play in their collaboration.

An algorithm for identifying chronic kidney disease in the French national health insurance claims database.

BACKGROUND: Published algorithms for identifying chronic kidney disease in healthcare claims databases have poor performance except in patients with renal replacement therapy. We propose and describe an algorithm to identify all stage chronic kidney disease in a French healthcare claims databases and assessed its performance by using data from the Renal Epidemiology and Information Network registry and the French Childhood Cancer Survivor Study cohort. METHODS: A group of experts met several times to define a list of items and combinations of items that could be related to chronic kidney disease. For the French Childhood Cancer Survivor Study cohort, information on confirmed chronic kidney disease cases extracted from medical records was considered the gold standard (KDIGO definition). Sensitivity, specificity, and positive and negative predictive value and kappa coefficients were estimated. The contribution of each component of the algorithm was assessed for 1 and 2 years before the start of renal replacement therapy for confirmed end-stage kidney disease in the Renal Epidemiology and Information Network registry. RESULTS: The algorithm's sensitivity was 78%, specificity 97.4%, negative predictive value 98.4% and positive predictive value 68.7% in French Childhood Cancer Survivor Study cohort and the kappa coefficient was 0.79 for agreement with the gold standard. The algorithm 93.6% and 55.1% of confirmed incident end-stage kidney disease cases from the Renal Epidemiology and Information Network registry when considering 1 year and 2 years, respectively, before renal replacement therapy start. CONCLUSIONS: The algorithm showed good performance among younger patients and those with end-stage kidney disease in the twol last years prior to renal replacement therapy. Future research will address the ability of the algorithm to detect early chronic kidney disease stages and to classify the severity of chronic kidney disease.

Women's Access to Kidney Transplantation in France: A Mixed Methods Research Protocol.

Kidney transplantation is the best renal replacement therapy (medically and economically) for eligible patients with end-stage kidney disease. Studies in some French regions and in other countries suggest a lower access to the kidney transplant waiting listing and also to kidney transplantation, once waitlisted, for women. Using a mixed methods approach, this study aims to precisely understand these potential sex disparities and their causes. The quantitative study will explore the geographic disparities, compare the determinants of access to the waiting list and to kidney transplantation, and compare the reasons and duration of inactive status on the waiting list in women and men at different scales (national, regional, departmental, and census-block). The qualitative study will allow describing and comparing women's and men's views about their disease and transplantation, as well as nephrologists' practices relative to the French national guidelines on waiting list registration. This type of study is important in the current societal context in which the reduction of sex/gender-based inequalities is a major social expectation.

Predialysis Care Trajectories of Patients With ESKD Starting Dialysis in Emergency in France.

INTRODUCTION: Emergency dialysis start (EDS) is frequent for patients with chronic kidney disease (CKD). To improve CKD management, new trajectory-based care policies are currently being introduced both in France and in the United States. This study describes the different types of predialysis care trajectories and factors associated with EDS. METHODS: Adults patients who started dialysis in France in 2015 were included. Individual clinical and health care consumption data were retrieved from the French national end-stage kidney disease (ESKD) registry (Renal Epidemiology and Information Network [REIN]) and the French National Health Data system (SNDS), respectively. Hierarchical Clustering on Principal Component was used to identify groups of patients with the same health care consumption profile during the 2 years before dialysis start. Logistic regression analysis was used to identify factors associated with EDS. RESULTS: Among the 8856 patients included in the analysis, 2681 (30.3%) had EDS. The Hierarchical Clustering on Principal Component identified six types of predialysis care trajectories in which EDS rate ranged from 13.8% to 61.8%. After adjustment for the patients' characteristics, less frequent or lack of follow-up with a nephrologist was associated with higher risk of EDS (odds ratio [OR]: 1.32; 95% confidence interval [CI]: 1.17-1.50 and OR: 1.83; 95% CI: 1.58-2.12), but not follow-up with a general practitioner. CONCLUSIONS: The care trajectories during the 2 years before dialysis start were heterogeneous and patients with a lesser or lack of follow-up with a nephrologist were more likely to start dialysis in emergency, regardless of the frequency of follow-up by a general practitioner (GP). New CKD policies should include actions to strengthen CKD screening and referral to nephrologists.

Analysis of the association between emergency dialysis start in patients with end-stage kidney disease and non-steroidal anti-inflammatory drugs, proton-pump inhibitors, and iodinated contrast agents.

BACKGROUND: The association between the use of potentially nephrotoxic drugs [Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), Iodinated Contrast Agents, Proton Pump Inhibitors (PPIs)] and emergency start of dialysis in patients with chronic kidney disease has not been well explored, although these compounds are commonly prescribed or available without prescription. METHODS: In this study, the Renal Epidemiology Information Network (REIN) registry data of all patients ≥ 18 years of age who started dialysis in France in 2015 were matched with those in the French National Health Insurance Database. The association between clinical characteristics, nephrotoxic drug exposure and emergency dialysis start was investigated. Patients were categorized into four classes of NSAID and PPI exposure (new, current, past, no user) on the basis of the pre-dialysis exposure period (1-30, 31-90, and 91-365 days). For iodinated contrast agents, exposure in the 72 h and 7 days before dialysis was analyzed. RESULTS: Among the 8805 matched patients, 30.2% needed to start dialysis in emergency. After adjustment for socio-demographic and clinical variables, new NSAID users were more likely to experience emergency dialysis start [OR = 1.95; 95% CI (1.1-3.4)]. This association was higher for new than for current users [OR: 1.44; 95% CI (1.08-1.92)]. Emergency dialysis start was also associated with iodinated contrast agent exposure in the previous 7 days [OR: 1.44; 95% CI (1.2-1.7)]. No significant relationship was detected between PPIs and emergency dialysis start. CONCLUSIONS: Using both clinical and healthcare data, this study shows that emergency dialysis start is independently associated with recent exposure to NSAIDs and iodinated contrast agents. This suggests the need to strengthen the information given to healthcare professionals and patients with regard to nephrotoxic drugs.

Contribution of medico-administrative data to the development of a comorbidity score to predict mortality in End-Stage Renal Disease patients.

Comorbidity scores to predict mortality are very useful to facilitate decision-making for personalized patient management. This study aim was to assess the contribution of medico-administrative data in addition to French Renal Epidemiology and Information Network (REIN) data to the development of a risk score to predict the 1-year all-cause mortality in patients with End Stage Renal Disease (ESRD), and to compare it with previous scores. Data from a derivation sample (n = 6336 patients who started dialysis in 2015 in France) obtained by linking the REIN and the French National Health Insurance Information System databases were analyzed with multivariate Cox models to select risk factors to establish the score. A randomly chosen validation sample (n = 2716 patients who started dialysis in 2015) was used to validate the score and to compare it with the comorbidity indexes developed by Wright and Charlson. The ability to predict one-year mortality of the score constructed using REIN data linked to the medico-administrative database was not higher than that of the score constructed using only REIN data (i.e., Rennes score). The Rennes score included five comorbidities, albumin, and age. This score (AUC = 0.794, 95%CI: 0.768-0.821) outperformed both the Wright (AUC = 0.631, 95%CI: 0.621-0.639; p < 0.001) and Charlson (AUC = 0.703, 95%CI: 0.689-0.716; p < 0.001) indexes. Data from the REIN registry alone, collected at dialysis start, are sufficient to develop a risk score that can predict the one-year mortality in patients with ESRD. This simple score might help identifying high risk patients and proposing the most adapted care.

The Pre-Dialysis Care Trajectory of Chronic Kidney Disease Patients and the Start of Dialysis in Emergency: A Mixed Method Study Protocol.

Chronic Kidney Disease (CKD) is an important public health issue that requires early and close medical monitoring to start Renal Replacement Therapy (RRT) in the best conditions. However, in France, about 1/3 of patients start dialysis in emergency, despite the existence of CKD management guidelines. Using both quantitative and qualitative methods, we wanted to analyze the pre-dialysis care trajectory of patients with CKD and document the causes of Emergency dialysis Start (ES). To this aim, we designed a convergent mixed-method study. The quantitative component will analyze individual healthcare consumption and clinical data to identify the risk factors of ES by comparing the trajectories of patients who started dialysis in emergency in 2015 in France with those of patients who started in a planned manner and with the national recommendations. The qualitative component will explore the patients' trajectories and identify barriers to a planned start using semi-structured interviews with patients who started dialysis in emergency and with their general practitioners and nephrologists. Using the strengths of a mixed methodology, this study will bring robust and valuable findings to improve the care of CKD patients.

Geographic Variations in the Risk of Emergency First Dialysis for Patients with End Stage Renal Disease in the Bretagne Region, France.

Emergency first dialysis start considerably increases the risk of morbidity and mortality. Our objective was to identify the geographic variations of emergency first dialysis risk in patients with end-stage renal disease in the Bretagne region, France. The spatial scan statistic approach was used to determine the clusters of municipalities with significantly higher or lower risk of emergency first dialysis. Patient data extracted from the REIN registry (sociodemographic, clinical, and biological characteristics) and indicators constructed at the municipality level, were compared between clusters. This analysis identified a cluster of municipalities in western Bretagne with a significantly higher risk (RR = 1.80, p = 0.044) and one cluster in the eastern part of the region with a significantly lower risk (RR = 0.59, p < 0.01) of emergency first dialysis. The degree of urbanization (the proportion of rural municipalities: 76% versus 66%, p < 0.001) and socio-demographic characteristics (the unemployment rate: 11% versus 8%, p < 0.001, the percentage of managers in the labor force was lower: 9% versus 13% p < 0.001) of the municipalities located in the higher-risk cluster compared with the lower-risk cluster. Our analysis indicates that the patients' clinical status cannot explain the geographic variations of emergency first dialysis incidence in Bretagne. Conversely, where patients live seems to play an important role.