targets were as follows: 30,3%, Kt/V; 33,6%, ... of 2003 was as follows: 52% haemodialysis (HD), 6% .... prevalent facility catheter use >10% versus
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DOPPS ESTIMATE OF PATIENT LIFE YEARS ATTRIBUTABLE TO MODIFIABLE HAEMODIALYSIS PRACTICES IN BELGIUM
Original articles
DOPPS ESTIMATE OF PATIENT LIFE YEARS ATTRIBUTABLE TO MODIFIABLE HAEMODIALYSIS PRACTICES IN BELGIUM M. Jadoul1, N. Lameire2, J.L. Bragg-Gresham3, M.A. Eichleay3, R.L. Pisoni3, F.K. Port3 Key words: DOPPS results, Belgium, life years gain, haemodialysis, guidelines
ABSTRACT Background:Various organizations have published clinical practice guidelines for the care of haemodialysis patients. However, it is unknown to what extent improving or even reaching perfect compliance with guidelines would improve the survival of HD patients in Belgium. Methods: Using data from the second phase of the Dialysis Outcomes and Practice Patterns Study (DOPPS), the proportion of haemodialysis patients failing to meet six key practice targets (Kt/V >1,2, haemoglobin >11 g/dl, phosphate 1,1-1,5 mmol/l, calcium 2,1-2, 4 mmol/l, albumin >40 g/l, and facility catheter use 20.000) of patients was selected from the participating facilities in all 12 DOPPS countries. Data from both DOPPS I and II were included because the relative mortality risks for the investigated practices are not expected to change over time and the combination of the two data sets allows for a more stable estimate based on the larger patient sample. Patients, aged 18 years or older and receiving chronic maintenance HD within a dialysis facility, were eligible for study participation, and a random sample of 20-40 patients (depending on the unit’s size) was enrolled at each site. The selected study patients provided longitudinal data on demographics, more than 65 indications of baseline comorbidity, measures of socioeconomic status, vascular access use, characteristics of HD treatment, delivered HD dose, and laboratory data, including measures of anaemia and mineral metabolism management. The percentage of patients outside each target was calculated based on data from a prevalent cross-section of Belgian HD patients (n = 538) upon entering the DOPPS II study and was weighted by the number of patients per facility to account for disproportionate sampling with respect to facility size. The estimation of the total Belgian HD patient population in 2006 was extrapolated from the outpatient HD patient population reported in the 2001 Flemish-speaking and French-speaking registries.(1.2) An average annual growth rate of 7,5% was applied to this population. This rate was observed for the HD popula-
DOPPS ESTIMATE OF PATIENT LIFE YEARS ATTRIBUTABLE TO MODIFIABLE HAEMODIALYSIS PRACTICES IN BELGIUM
tion in Belgium between 1997 and 2001.1,2 For the models of life years gained over 5 years, a constant number of new patients was assumed to enter the population annually. However, this estimation may be conservative because it does not account for annually increasing numbers of incident patients. Definition and Selection of Target Ranges Selection of the six characteristics of HD practice was based on three qualities: they are modifiable through changes in practice; they are associated with mortality; and, for each, a large proportion of the patient population has values outside the target range. The following targets were used to define “within guidelines”: dialysis dose (single pool Kt/V >1,2), anaemia management (haemoglobin >110 g/L), albumin (≥40 g/L), serum phosphorus (1,1-1,5 mmol/L), albumin-corrected serum calcium (2,1-2,4 mmol/L), and facility catheter use (≤10%). All values, except phosphorus, represent the KDOQI guidelines.19 Belgian experts provided the phosphorus target value to represent common goals for clinical practice. Standardization of Albumin Standardization occurred in three steps. First, a “standard” reference population (popn) serum albumin mean (4,25) and range (3,5-5,0) was assumed. Second, patient serum albumin values in each facility were centered and scaled according to the serum albumin reference range reported by the facility’s laboratory.20 As a last step, this facility reference range was applied to the “standard” reference range by the following equation: Standardized Patient Serum Albumin Value = Standard Reference Popn Mean + (Reported Patient Serum Albumin Value - Facility’s Reference Popn Mean)*(Standard Reference Popn Range/Facility’s Reference Range) Where: Standard Reference Popn Range = 3,5-5,0 Standard Reference Popn Mean = (3,5 + 5,0)/2 = 4,25 Facility’s Reference Popn Mean = (facility reference range low + high value)/2 The standardized patient serum albumin values were used in some of the statistical analyses to investigate the sensitivity of results to laboratory standardization.
Statistical Analysis Cox proportional hazards regression models were used to calculate the relative risk of mortality for all patients outside each guideline described above, using data from DOPPS I and DOPPS II. These models were stratified by country and phase of study. Data from the time of patient entry into the DOPPS were modelled separately for each of the six haemodialysis practices as follows: single pool Kt/V 1,2; PO4 >1,5 mmol/L versus 1,1-1,5 mmol/L (adjusted for PO4 2,4 mmol/L versus 2,1-2,4 mmol/L (adjusted for Ca 10% versus
