Brazilian Registry of Bone Biopsy ( REBRABO ) : design , data elements and methodology

1 University of São Paulo. 2 State University of Campinas. 3 Pontifical Catholic University of Paraná. 4 Federal University of Pernambuco. 5 Ana Neri Hospital. 6 Porto Alegre University Hospital, Federal University of Rio Grande do Sul (UFRGS). 7 Fluminense Federal University. 8 Federal University of São Paulo. 9 Chronic Kidney Disease Mineral and Bone Disorders (CKD-MBD) Committee of the Brazilian Society of Nephrology (SBN).

Introduction: Mineral bone disorder (MBD) is a common condition in chronic kidney disease (CKD) patients and causes significant morbidity and mortality. Data involving prevalence of alterations in bone histological patterns, impact of different treatments and its repercussion in outcomes, such as bone fractures, hospitalization, cardiovascular disease and mortality, are scarce. Data bank registry can be a valuable tool to understand epidemiological aspects of MBD CKD. The Brazilian Registry of Bone Biopsy (REBRABO) will be a national registry, coordinating by the Brazilian Society of Nephrology -Committee of MBD-CKD. Objective: To describe REBRABO´s design, elements of data and methodology. Methods: Will be an online national observational and multicentric data registry divided in two phases (retrospective, 1 st phase) and prospective (2 nd phase), including information from bone tissue histomorphometric analysis and demographics, clinical and laboratorial data from CKD-MBD patients. Results: The REBRABO´s first phase will explore data on demographics, clinical, laboratorial and bone histomorphometric analysis data from January/1986 to December/2013. The first results are expected in early 2015. Conclusion: Studies in the field of CKD-MBD are needed, particularly those analyzing its prevalence, associations between demographic, clinical, histological parameters, and major outcomes. The REBRABO will be a unique retrospective and prospective research platform including bone biopsy data in CKD-MBD patients.

IntroductIon
Mineral and bone disorders (MBD) are frequent in patients with chronic kidney disease (CKD) and they increase morbidity and mortality in these patients. 1 These disorders are known by the CKD-MBD acronym and encompass biochemical changes, vascular and soft tissue calcifications, and renal osteodystrophy (RO), which makes up the bone diseases in CKD patients. 2 Knowledge on the pathophysiology, diagnosis and treatment of CKD-MBD has increased substantially in recent decades. [3][4][5][6] Despite the advent of new bone remodeling biochemical markers, 7,8 bone biopsy is still considered the gold standard for RO diagnosis. 2,9 In Brazil, few laboratories analyze bone tissue without prior decalcification, with bone remodeling quantification by histomorphometry. It is estimated that in the last 30 years, around 5,000 patients with CKD-MBD were studied employing this technique. These biopsies were analyzed mainly at the University of São Paulo (USP) and Federal University of São Paulo (UNIFESP), providing a wealth of data that needs to be computerized, processed and made available to the scientific community.
There are few studies in the literature that assess the prevalence of different types of RO, as well DOI: 10.5935/0101-2800.20140050 as the impact of treatment and its effects on outcomes such as fractures, hospitalization, cardiovascular disease and mortality. In our setting, one study assessed the types of RO in 2,340 patients with stage 5D CKD (93.1% in hemodialysis), from 1985 to 2001. 10 The results of this study showed an increased prevalence of secondary hyperparathyroidism related to bone disease and reduced prevalence of aluminum-intoxication in the 90s compared to the 80s.
New guidelines for the diagnosis and treatment of CKD-MBD were introduced in recent years, changing previously established paradigms. [11][12][13] The prevalence of different types of RO has been modified over the last decade, especially the increased prevalence of static bone disease. [14][15][16] However, more studies are needed for understanding the pathophysiology of CKD-MBD, its complications and the impact of therapy, with the goal of contributing to quality of life improvement and reducing the high mortality rates of these patients.
Within this context it is necessary to create records that identify the different types of RO, risk factors, symptoms and complications associated with these disorders. The Brazilian Registry of Bone biopsies (REBRABO) will be a national, multicentric, observational database, coordinated by the Chronic Kidney Disease Mineral and Bone Disorder (CKD-MBD) Committee of the Brazilian Society of Nephrology (SBN). This register will examine demographic, clinical, laboratorial and histomorphometric parameters from bone tissue of patients with CKD-MBD retrospectively and prospectively.
REBRABO's primary mission will be to identify associations between variables mentioned and their relationships with clinical outcomes. This information will serve as a research platform to expand the knowledge about CKD-MBD. dAtAbAse And methods REBRABO will be a database containing demographic, clinical and laboratorial data on CKD-MBD patients submitted to bone biopsy, as well as the results of these biopsies. Data will be added by electronic means only, online, via a website physically located in computers at the private data center, contracted for this purpose (e.g., Locaweb). The database is programmed in "PHP" languages (Hypertext preprocessor), "JavaScript", "HTML" (Hypertext Markup Language) and "Css" (Cascading Style Sheets), and is managed by MySQL system. Such data inclusion is to be performed by licensed physicians only, previously registered in the SBN or REBRABO database or through user authentication via individualized password.
Initially (retrospective phase), we analyzed data from patients submitted to bone biopsies between 1986 and 2013, which processing and reports were carried out by the Kidney Hospital Bone Histomorphometry Labs/Oswaldo Ramos Foundation, Federal University of São Paulo (UNIFESP), São Paulo, Brazil, and Bone Histomorphometry Laboratory of the Kidney Pathophysiology -LIM-16, School of Medicine, University of São Paulo, São Paulo, Brazil. In the prospective phase we included patients whose bone biopsies were indicated by their physicians, or patients who participated in clinical trials approved by a medical ethics and research committee. There will be no REBRABO interference on the indication of bone biopsy, or treatment of any patient.
These data will be organized and scanned according to a standard electronic form (Table 1, Figure 1, Appendices 1, 2 and 3). When the bone tissue analysis report becomes available, it will be included in REBRABO through a standard electronic form (Figure 2 and Appendix 4). For data analysis, researchers may use filters to exclude records that do not meet the specific criteria of each research.
To increase the communication potential and facilitate scientific research, REBRABO will adopt the terminology recommended by the Kidney Disease Improving Global Outcomes (KDIGO) guidelines, through the TMV classification [Turnover Mineralization and Volume]. 2 Quantitative histomorphometric data, when available, will be grouped according to the structural parameters of formation, resorption and mineralization, which nomenclature follows the standards of the American Society for Bone and Mineral Research (ASBMR) 17 (Tables 2 and 3).
REBRABO data will be validated before its analysis. This process will take place by the very program structure, which will control data inclusion, preventing incorrect data entry. We have to bear in mind that all records will be checked by two different observers with experience in clinical research. Data analysis will be descriptive and plotted on a frequency table for categorical and analytical variables, continuous variables which will be represented as mean ± standard deviation or as median and interquartile ranges, as appropriate. Groups with normal distribution will be compared using the Student t-test or ANOVA; and the Mann-Whitney or Kruskal-Wallis tests for groups with non-parametric distribution. Categorical variables will be analyzed using the chi-square or Fisher test. Correlation analysis between continuous variables will be made by the Pearson (parametric data) or Spearman (nonparametric data) tests. Statistical analysis will be performed using the SPSS software version 17.1. The p < 0.05 value will be considered statistically significant.

Data use anD sharing
Researchers outside the CKD-MBD SBN committee can access REBRABO data upon request to the aforementioned Committee, through a standardized form. Applicants must sign a document accepting the use of data, confidentiality and publications terms and destruction of data after use. No data from REBRABO will be provided without signing this term of acceptance and work plan approval, or before the main analyses and publications from the CKD-MBD SBN Committee.

Document Description
Demographic/Clinical Census (Appendix 1) Form used to collect demographic characteristics and clinical information from each patient. We will collect data such as age, gender, ethnicity, CKD etiology, kidney disease duration, time in dialysis, dialysis mode, comorbidities, history of fractures, cardiovascular events, and others.
Laboratorial census (Appendix 2) Form used to collect laboratorial information in the last 6 months related to the bone biopsy date, including the following tests: ion calcium and/or total; phosphorus; alkaline phosphatase -total or bone fraction, parathyroid hormone(PTH); 25(OH)-vitamin D; creatinine; urea; hemoglobin; hematocrit; platelets; leucocytes; albumin; ferritin; aluminum; and others.
Bone tissue data analysis (Appendix 3) Form used to collect information on bone histology according to quantitative and semiquantitative histomorphometric parameters (Table 3 and Appendix 3).

PrOtectiOn Of research suBjects
The coordinator of the REBRABO will send data to the participating center preserving the patient's identity. There will not be any form of influence on patient bone biopsy or treatment indications, emphasizing that this database is only observational. It's up to each physician participating in REBRABO to obtain the consent of each patient, as well as signing and keeping

conclusIon
There is a paramount need for studies assessing the prevalence, associations between sociodemographic, clinical, laboratorial and bone-tissue histomorphometric variables and their relationships with clinical outcomes in the CKD-MBD field. REBRABO will be one of the largest databases of bone biopsies from patients with BMD, especially associated with CKD, and will serve as a research platform for future studies in this field.