Comparison of hernia registries: the CORE project

Randomized clinical trials (RCTs) and meta-analyses are considered the gold standard of evidence-based medicine nowadays [1]. The strength of RCTs rests on their excellent internal validity, which is based largely on the power of randomization to ensure that the only difference between two treatment arms is their exposure to the treatment of interest [2]. But the applicability of RCTs to the care of patients in routine practice is limited. In particular, patients, providers, and concurrent care in the general population are different from those in RCTs, and the generalizability or external validity of RCTs may be limited. Although observational research does not reach the same level of internal validity as RCTs, well-designed observational studies can offer high external validity and provide a unique opportunity to evaluate treatments and their outcomes in routine practice [2]. Many important clinical questions have not, cannot, and will not be addressed in the context of an RCT. In these situations, clinicians rely on information provided by observational research [2]. In a comparison of observational studies and RCTs, the estimates of the treatment effects from observational studies and RCTs were similar in most cases [3]. Registries are ongoing prospective observational data-collection repositories [4]. A registry is defined as a systematic collection of a clearly defined set of health and demographic data for patients with specific health characteristics, held in a central database for predefined purposes [5]. Medical registries can serve different purposes, for instance as a tool to monitor and improve the quality of care or as a resource for research [5]. To be useful, data in a medical registry must be of good quality [5]. To optimize the quality of medical registry data, the participating centers should follow certain procedures designed to minimize inaccurate and incomplete data [5]. The intended use of registry data determines the necessary properties of the data [5].

In 1992, surgeons from eight Swedish hospitals initiated a registry for inguinal and femoral hernia repair [6]. The aim of the registry was to report on the operative techniques used and to analyze outcome measures in order to stimulate quality improvement [6]. A number of national and international registries have since been added [6‐12].

The aim of this manuscript is to explore the databases of these hernia registries and compare them in content and outcome variables.

The CORE (Comparison of Hernia Registries in Europe) project was initiated with representatives from all established European hernia registries in March 2015 in Berlin. Initially perceived as a European project, the scope was broadened to also include the Americas Hernia Society Collaboration (AHSQC) Registry. Each registry representative was contacted to present and verify information regarding the registry (Table 1).

The following information was obtained: Country(ies) of use, start date of registry, procedures included, compulsory or voluntary data entry, overseeing body, funding, user cost, access route, language, number of active users, whether data are validated and by what method, data analysis provided, and how the data are published. The following categories were used to compare the registries: initiation and funding, data collection and use for certification of hernia centers, patient data and data protection, operative data, registration of complications and follow-up data.

The timeline for launch of registries included in the CORE project is shown in Fig. 1. Prospective hernia surgery registration was pioneered by Erik Nilsson in 1992 with the Swedish Groin Hernia Registry (SGHR) [6]. In 1998 the Danish Groin Hernia Database (DGHD) was established and was subsequently extended to ventral hernias (Danish Hernia Database) in 2007 [7]. The German Herniamed Registry included both inguinal and ventral hernias and was launched in 2009 [9]. In France the Club Hernie (CH) started their ventral hernia registry in 2011 across 30 specialized hernia surgeons [10]. Two registries were launched in 2012: EuraHS [8], and the Spanish Registro Español de Eventraciones (EVEREG) [11]. The Americas Hernia Society Collaboration (AHSQC) Registry followed in 2013 [12].

Within the scope of the CORE project, representatives from seven hernia registers gathered to compare different aspects of their hernia registers. The CORE project examined aspects such as financing, data collection, certification, patient data, operative data, complications and follow-up of the patients. As registries were developed during various time periods where hernia surgery techniques and focus on outcomes have differed over time, differences between registries can be found. Financial resources have also had an impact on the quality of registries as have the ideas of individual surgeons.

It would be desirable to directly compare and combine data from the various hernia registries; therefore, the present analysis suggests potential adjustments to the way data are collected to improve data comparability in the future. The recommendations for reporting outcomes should be given particular attention [13].

Despite the differences in the way data are collected for each of the listed hernia registries, the data are indispensable in clinical research. As a consequence of the numerous innovations in hernia surgery (surgical procedures, meshes, fixation devices), hardly any other area of surgical study has such a high need for clinical trials and data collection, comparison and analysis. Registries play a vital role in this innovation process [14]. In addition, there is insufficient public funding available to perform RCTs [15, 16]. Furthermore, the costs for conducting RCTs have increased dramatically over the last decades [17]. Therefore, RCTs should be more feasible embedded within registries [18].

It has been shown that the introduction of the Danish Hernia Database improved the quality of inguinal hernia surgery from a national perspective [19]. A review based on three European hernia registries demonstrated the range of insightful findings that can be gleaned from hernia registries [20]. Registries can also play an important role in monitoring new devices by the industry (post marketing surveillance) [21]. This is of paramount importance as registries are called upon to provide more data for this specific purpose, because in the context of the current regulation environment at least in the European Union countries, the need of post marketing surveillance of medical devices has increased. As the main aim of the new European Union Medical Device Regulation is better patient safety industry, insurance companies and governments should ultimately contribute to fund hernia registries.

Currently, over 170 analyses from various hernia registries (Danish Hernia Database—http://​www.​herniedatabasen.​dk 84; Swedish Hernia Registry—http://​www.​svensktbrackregi​ster.​se 55; Herniamed—http://​www.​herniamed.​de 22; EuraHS—http://​www.​eurahs.​eu 5; AHSQC—http://​www.​ahsqc.​org 5; Club Hernie—http://​www.​club-hernie.​com 1; EVEREG—http://​www.​evereg.​es 1) have been published. The number of published articles clearly indicates that RCTs and registry-based observational studies have become partners in the evolution of medical evidence in hernia surgery [20]. As there is a discrepancy between the actually published data from hernia registries and the number listed in PubMed the use of the registry name as key word for the publication should be obligatory.

Many important questions in the field of hernia surgery have only been studied in registry studies [20]. Thus, the registers in hernia surgery are of great importance for clinical research. One clear advantage of the registry concept is having the ability to detect and analyze low rate potentially clinically relevant or even catastrophic events. Due to the increasing complexity in hernia surgery, hernia centers are increasingly being established worldwide [22].

Public media are increasingly aware of the fact that surgery can only be improved if its results are known [23]; the registry data are increasingly used for quality control [24], for example, in the certification of hernia centers [25]. A hernia center should be required to participate in a registry and submit as complete as possible data on all hernia patients [25].

Limitation of all data analysis from registries is always selection and input bias. The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) mandates that participating hospitals assigns a NSQIP trained clinical reviewer to collect data on a stratified sampling of patients. Ongoing education for the reviewers as well as auditing is designed to ensure data reliability. This can be a model for the future, but calls for adequate financial support. This model can also prevent misuse of a registry by participating hospitals for marketing purposes.

In summary, while the seven existing hernia registries worldwide may differ in structure, together they contribute to raising the quality of hernia surgery. Assurance of data quality is critical to registries. This aspect should be taken into account in the evaluation of registry data. It would be desirable to harmonize outcome variables. The registries are of great importance for clinical research and are complimentary to RCTs for quality assurance, monitoring innovations, and potential certification of hernia expert centers. Combining all registry data in a common database would be desirable to allow additional knowledge to be gained.