Objectives

The aim of the Norwegian Kidney Biopsy Biobank (NorKiBB) is to improve knowledge and outcomes for CKD patients by providing researchers access to high quality bio-specimens and associated clinical data concurrent with kidney biopsy data. To this end, we wanted to establish a population-based cohort to provide generalizable results. This biobank initiative aims to improve the collaboration among clinical, pathological, epidemiological, molecular, and genetic research environments to generate new knowledge generalizable to the clinical kidney communities.

CKD healthcare in Norway

All healthcare in Norway is organized and funded by the national government, and all levels of care are free for all citizens. General practitioners serve as gatekeepers and decide whether a referral to a nephrologist or hospital admittance is needed. Kidney biopsies are performed by radiologists or nephrologists at 20 different hospitals across Norway, and further histopathological examination is conducted at one of the four university hospitals that have a dedicated nephro-pathology service. Currently, the kidney biopsy frequency is 98 per million population per year [9]. The incidence of kidney failure necessitating renal replacement therapy (RRT, i.e. dialysis or transplantation) is 98 per million per year, and 10% of RRT patients receive a preemptive kidney transplant [10].

Recruitment of patients

All hospitals that perform kidney biopsies in Norway were invited to participate (Fig. 1). All adult patients referred for a routine kidney biopsy by their treating nephrologist on clinical indication were eligible for inclusion. Patients were excluded if they were not able or willing to give a written informed consent. Inclusion started September 2020. Recruitment is still ongoing.

Fig. 1

A map of Norway, with the participating centers (red dots) and the non-participating centers (white dots). Source and copyright: The authors

Collection and preparation of bioresources

All participants undergoing native kidney biopsy donated blood and urine at the outpatient clinic or the inpatient ward during the 48 h prior to the biopsy procedure. All centers used the same standard operating procedure (SOP) for collection, preparation, aliquoting, and storage of urine, blood, and kidney tissue. In addition to standard biochemical tests needed for full evaluation of kidney diseases and biopsy preparation, extra blood and urine were obtained for long-term storage in the biobank. Blood was drawn for 2 × 5 mL Vacutainer SST II serum tubes, then centrifuged at 2200 G for 10 min after 30 min in room temperature, aliquoted into 0.5mL tubes and frozen at -80 °C. Blood was also drawn for 3 × 6 mL Vacutainer EDTA tubes, immediately centrifuged at 2200 G for 10 min at 4 °C, plasma was aliquoted into 0.5mL tubes, and the remaining plasma and buffy coat (leucocytes and thrombocytes) was transferred to 0.5mL tubes. All tubes were immediately frozen at -80 °C. Sixty to 100 mL of mid-stream second urine of the day was collected in a 120 mL plastic cup and transferred to 6 × 10 mL vacutainer tubes. Two 4.5 mL aliquots of raw urine were frozen at -80 °C without centrifugation or additives. The remaining urine was centrifuged at 1000 G for 12 min at 4 °C, and protease inhibitor (Protease Inhibitor Cocktail P1860, Sigma) was added to 4 × 4.5 mL aliquots. Another six 4.5 mL aliquots were frozen without protease inhibitor. We added RNA-later (R0901, Sigma) to the remaining cell pellets and transferred the solution to three 0.5 mL tubes. Kidney biopsy samples were handled by the standard protocols of each of the four nephropathology centers, including ordinary preparation for standard histological staining for light microscopy, immunofluorescence or immunohistochemistry, and electron microscopy. All slides were described histopathologically by two of the nephro-pathologists at the regional pathology center. Subsequently, four unstained slides were prepared from the remaining material and stored at -80 C.

Storage of biological samples

Blood and urine aliquots were stored locally and later sent to Biobank1 in Trondheim in batches of 20 patients. The samples were packed in Styrofoam boxes filled with dry ice and sent express with a commercial courier to the biobank with transportation time less than 24 h. Biobank1 is a joint project between the Norwegian University of Science and Technology (NTNU) and the Mid-Norway Regional Health Authority to store data and biological samples for research purposes in Central Norway. Biobank1 organized de-identification of data, barcoding samples, storage and tracking of samples and related information. Samples were stored according to best practice, at -80 °C with temperature logging and alarm system. Kidney biopsies were also scanned and deposited digitally in the Norwegian Renal Registry.

Data security and collection of medical history and risk factor data

We used a web-based system for registration of medical data (eForsk, Helse Midt-Norge IT, Norway). This is a two-way encryption solution with two-factor authentication enabling safe transfer of sensitive patient information via the closed Norwegian Health Network. In this way, patient identifiable information can be entered locally by the treating nephrologists who have the most comprehensive medical information of the patient and transferred directly to the biobank without the need for a local encryption key. Standardized questions on medical history, indication for biopsy, risk factors, medications, diagnostic tests (antineutrophil cytoplasmic antibodies ANCA, antinuclear antibodies ANA, complement, and other serological testing), procedure complications, and other queries were answered by the local nephrologist using a combination of pull-down menus and free text sections. A complete list of variables is available in the Supplementary Table 1.

Biochemical tests used for the baseline kidney evaluation

To fully characterize all patients at the time of the kidney biopsy, a standard test panel was analyzed locally. This included a complete blood cell count, bleeding risk evaluation, electrolytes, kidney function, analytes for glucose and lipid metabolism, and others. Urine was tested with a dipstick, and electrolytes, albumin, creatinine, and osmolality were quantified. See Supplementary Table 1 for complete list of the 42 analytes measured. All measurements were done in the clinical laboratories of the participating hospitals.

Kidney biopsy procedure and histological examination

The most widespread biopsy procedure in Norway is for patients to have two kidney core biopsies taken with a 16G needle. The biopsies are sent to the regional nephro-pathology laboratory, where routine examinations are performed: standard light-microscopy staining (hematoxylin-eosin HE, Periodic acid-Schiff PAS, silver, Congo red), immunofluorescence or immunohistochemistry (IgA, IgG, IgM, C3, C4, C1q, kappa and lambda free light chains), and electron microscopy (in > 90% of the cases). Results are then typically examined by two nephro-pathologists. The clinical reads from the nephro-pathologists were used as the biopsy description in our biobank.

Data from all Norwegian kidney biopsies, i.e., both those included in the NorKiBB and those not participating, are sent to the Norwegian Renal Registry. This is a national quality registry for patients with CKD stage 5, renal replacement therapy, or kidney biopsies. The entries include the full histology report, a selected sub-set of clinical and laboratory data, a HE stained digitalized whole slide image, but no biospecimens.

Ethics

The NorKiBB was approved by the Regional Committee for Medical Research Ethics Central Norway, as well as by the local data protection boards/data access committees in all of the participating hospitals: the Data Protection Officer at St. Olavs Hospital, Trondheim University Hospital, Trondheim; the Regional Committee for Medical Research Ethics Western Norway for Haukeland University Hospital, Bergen; the Data Access Committee at Levanger Hospital, Levanger; the Data Protection Officer at Lillehammer Hospital, Lillehammer; the Data Protection Officer at Oslo University Hospital, Ullevål, Oslo; the Data Protection Office at Akershus Oslo University Hospital, Lørenskog; the Data Protection Official at the University Hospital of North Norway, Tromsø; and The Research Department at Stavanger University Hospital, Stavanger. All patients gave their written, informed consent after having received oral and written information about the project, possible disadvantages, and benefits in accordance with the General Data Protection Regulation (GDPR). A copy of the consent form is available in the Supplementary section. All experiments were performed in accordance with the Norwegian Act on medical and health research, and the Personal Data Act. The experiments were conducted in accordance with the Declaration of Helsinki.

Funding and costs

The NorKiBB was established as part of the project “Kidney Tubular Damage and Dysfunction Identify a Novel Axis of Chronic Kidney Disease”. This is a joint US - Norwegian project funded by the U.S. National Institute of Health and the Norwegian Research Council. The project aims to assess the relationships of a wide range of blood and urine tubulointerstitial biomarkers with histopathological manifestations of kidney health. A Norwegian national biobank with data and samples from patients undergoing clinical kidney biopsy was initiated with the aim to collect sufficient material to enable further research projects beyond the Kidney Tubular Damage project. The biobank was named NorKiBB. Recruitment of patients, registration of data, analyses for standard CKD evaluation, and histopathology were considered part of the ordinary hospital practice and therefore not directly reimbursed. The laboratories were reimbursed for extra materials and personnel needed for preparation, registration, local storage, and transportation of biomaterial to BioBank1. Biobank1 also charges a rather small annual amount for storage of samples, so the total costs for establishing and including this first wave of patients were rather low.

External resources of relevance for the realization of the biobank

Linkage to external resources is quick and accurate using the unique eleven-digit identification number given to all Norwegian citizens at birth or at immigration. Norway has a long tradition for medical registries, and mandatory reporting to multiple central registries can give highly relevant information for kidney researchers (e.g., medical birth registry, cause of death registry, medical drug prescriptions registry, cancer registry, and others). In addition to the kidney disease registry mentioned above, there are similar registries for myocardial infarction, heart failure, stroke, peripheral vascular disease, diabetes, bariatric surgery, vascular surgery, vasculitis, and others.

The public specialist health care system in Norway is mainly funded by the Norwegian federal government and organized in regional health trusts. Private nephrology clinics are almost non-existing. For CKD patients, this means that their general practitioner, the nephrologist at the outpatient clinic, and all laboratories and hospitals are part of the same organization. This enables unique possibilities for cooperation for both clinical practice and research.

Governance

The NorKiBB is a very small organization with no personnel directly employed at the biobank. The Steering Committee is composed of active kidney researchers from the five Norwegian university clinics in Trondheim, Tromsø, Bergen, and Oslo (see Acknowledgements). They provide general oversight of the biobank activities, review and adjudicate incoming research application requests, and discuss future targets and funding opportunities. Day to day activities are managed by the Kidney Research Group at NTNU/St. Olavs Hospital and by personnel at Biobank1.