This observational multinational multi-centre prospective study comprised 1619 ESRD patients who started dialysis over a 3-year period at 15 nephrology departments from seven Nordic and Baltic countries. The methodology of the “Peridialysis” project has been previously described [42-44]. All centers delivered both PD and in-centre HD; some also home-HD; all had a developed and working multidisciplinary pre-dialysis care team structure with nephrologists and experienced nurses; 13/15 centers also had access to a dietician, and 5/15 had access to social worker.
The commonest method of assessing residual renal function and guiding clinical treatment was estimated glomerular filtration rate (eGFR) as measured by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula .
Patients included in this study were consecutive patients starting chronic dialysis therapy for end stage renal disease (ESRD) at the participating centers between January 1, 2015 and December 31, 2017. Five centers had a shorter recruiting period.
A patient was considered as having ESRD at first dialysis if:
- The patient was diagnosed as having ESRD according to the treating physician; this was the most used definition of ESRD.
- The patient received dialysis treatment for >90 days.
- If the doctor was in doubt whether the patient had acute or chronic renal failure, the patient was included retrospectively as soon as there was no doubt that the patient had chronic renal failure and ESRD.
The study protocol was approved by the ethical review boards in centers located in countries where according to the country´s regulations this was required. The study was approved by the Swedish Ethical Review Authority (Ref 2017/7), while in Denmark, due to the observational non-interventional design of the study using anonymized patient data, the study protocol was not considered to be eligible for ethical review. Informed consent - either written or verbal depending on the regulations in the different countries - was obtained from participants in all centers including those in Denmark, with the exception of Lithuania, where patient permission was waived by the ethics board (P2-BE-2-9/2014). The study is registered with Clinical Trials.gov, identifier NCT02488200. The Swedish approval was valid for all EU countries.
Patient clinical data
The following data were registered at DI: patient characteristics (age, sex, height, body weight, body mass index (BMI) and underlying renal diagnosis), selected comorbidities (previous myocardial infarction, heart failure, cardiac atherosclerosis, cerebrovascular disease, diabetes, peripheral atherosclerosis, previous cancer (except basocellular), chronic pulmonary disease, chronic liver disease, psychiatric disease, and “other chronic conditions”), previous renal transplantation, and dialysis access. Data on dialysis access was used to classify if the start of dialysis as optimal DI or suboptimal DI.
DI was classified as optimal if:
- The access was an AVF or graft (AVG);
- The access was a tunnelled vascular catheter as the patient’s permanent access due to a medical decision;
- The access was a PD catheter, and PD was started >6 days after placement.
DI was classified as suboptimal if:
- The access was a temporary vascular catheter;
- The access was a tunnelled catheter, but a later AVF/AVG was planned;
- The access was a PD catheter, and PD was started <6 days after placement.
Late referral was defined as referral to the specialist clinic <3 months before DI.
As pre-emptive transplants were often assessed and treated at other departments, patients receiving pre-emptive transplants were excluded from the study.
Modality choice was planned by shared decision making before DI or shortly thereafter. Primary causes of choice of dialysis modality choice included preference for PD (HD not possible); preference for HD (physical contraindication to PD); preference for HD (mental contraindication to PD); preference for HD (abdominal contraindication to PD); preference for HD (home dialysis modality not discussed); and other. The remaining patients could choose between PD, in-centre HD and home HD depending on their personal preferences. Changes in modality during the first year after DI were registered.
Patient biochemical data
The following biochemical data prior to or in conjunction with first dialysis were registered: blood hemoglobin, plasma concentrations of urea, creatinine, potassium, hydrogen carbonate (bicarbonate), albumin, C-reactive protein (CRP), total or ionized calcium, and phosphate. Most centers measured ionized calcium; for other centers, ionized calcium was assumed to be 50% of total calcium. Whenever available, plasma creatinine concentration and date of measurement were registered about three and six months before DI.
Rapid rate of loss of eGFR was defined as a fall of eGFR >1 ml/min/1.73m2/month.
Reasons for dialysis initiation stated in questionnaire to physicians
Physicians gave details in an English language questionnaire of their reasons for prescribing chronic dialysis at DI. They could choose between several pre-stated clinical and/or biochemical reasons. Details of these have already been published. [42-44]. For the purposes of the present study, clinical symptoms were registered if they were the primary cause of DI. Life-threatening conditions were defined as presence of pulmonary stasis, dyspnea, cardiac symptoms, pericarditis, acidosis or hyperkalemia. Clinical reasons (rather than biochemical) were stated to be the primary cause of DI in 63% % of patients .
Data are presented as mean ± standard deviation (SD) for normally distributed variables, median (interquartile range, IQR) for non-normally distributed variables, or as numbers and percentage. Parametric variables were compared using the Students t-test and MANOVA, and non-parametric variables using the Chi square, Mann-Whitney and Kruskal-Wallis tests.
Kaplan Meier and forward stepwise Cox proportional hazards analysis were performed to identify independent factors associated with mortality during the first year of dialysis. Patients were censored for lost-to-follow-up or transplantation.
Forward stepwise regression analysis was performed to identify independent associations with modality choice. Four models were analysed; all models included age, sex, comorbidity, plasma albumin and renal diagnoses, and in addition selected variables as follows: “Predialysis” model included predialysis variables: rate of eGFR change per month prior to DI, late referral and suboptimal DI. “Biochemical” model included selected biochemical variables at DI. “Clinical” model included those clinical problems that were stated as the primary cause of DI. “Combined model”, a final model that included all factors that were statistically significant in the previous three models.
A probability level of <0.05 was considered significant. Significance values were expressed as p<0.05, p<0.01, p<0.001.