Data Definitions

A number of definitions given below are used throughout the annual report unless otherwise stated.
Click on a heading to expand or collapse.

  • Wording

    Throughout the annual report ‘treatment’ refers to renal replacement therapy, including haemodialysis, peritoneal dialysis and transplantation. In places the word “graft” (or “allograft”) is used for kidney transplant.

    HD = haemodialysis
    CAPD = continuous ambulatory peritoneal dialysis
    APD = automated peritoneal dialysis
    ESKD = end stage kidney disease

  • Data Collection

    ANZDATA collects information from all renal units in Australia and New Zealand. Data collection occurs at two time points. Key events (new patients, deaths, transplants) are notified as they occur, with units requested to send this at least monthly. This can occur either via a web-based interface or paper submission. An extensive cross-sectional survey is then performed annually (for data to 31st December). Currently this is by a paper-based system, with manual completion of the form and manual data entry. No formal audit mechanism is in place at this stage.

    For kidney transplants, HLA matching and panel reactive antibodies are obtained direct from the National Organ Matching System.

    Monthly summaries are distributed to the contributing units. Results contained in the annual report are based on a final database locked and prepared after the end of year survey returns are received.

  • Inclusion Criteria

    Included in the Registry are all patients resident in Australia or New Zealand receiving renal replacement therapy where the intention to treat is long-term, i.e. medical opinion is that renal function will not recover. Cases of acute renal failure are excluded. People who move overseas permanently are censored at date of last treatment (or departure in the case of transplant recipients).

  • Modality Attribution

    For survival analysis the initial mode of dialysis is generally determined at 90 days after first treatment, to allow for early changes and maturation of access. Other transfers (between modalities, or from satellite to hospital haemodialysis etc.) are not analysed if less than 30 days, except for transfers between dialysis centres to which a 60 day rule is applied to allow for holiday movements.

  • Underlying Renal Disease

    This is recorded by the treating hospital according to a modified EDTA coding system (details on back of survey form).

  • Deaths

    Death rate is predominantly reported as number of patients died/total number of years of treatment of all patients treated at any time during the year. It is expressed as deaths per 100 patient years (pt yrs) at risk.

  • Comorbid Conditions

    These are recorded by the treating hospital. No formal definitions are supplied; the treating clinician is asked to record whether the patient has coronary artery disease, chronic lung disease, cerebrovascular disease, peripheral vascular disease or diabetes according to their clinical opinion on a yes / suspected / no basis.

  • Transplant Waiting List

    The active transplant waiting list is based on data from the National Organ Matching System (Australia) linked probabilistically with ANZDATA.

  • Derived Measures

    Haemoglobin

    Haemoglobin is recorded as the last available measurement before the end of the survey period.

    Erythropoietic agents

    Erythropoietin agent use is recorded as “yes” if these agents were used at any time during the survey period.

    Iron studies

    Iron studies are requested within the last three months of the survey period.

    Estimated glomerular filtration rate

    Where glomerular filtration rate is estimated from serum creatinine at entry or post transplantation, the CKD-EPI formula is used:(1)

    Females with Cr<=62 micromol/L: eGFR = (144 + 22 if black) x (Cr/0.7)^-0.329 x 0.993^age

    Females with Cr>62 micromol/L: eGFR = (144 + 22 if black) x (Cr/0.7)^-1.209 x 0.993^age

    Males with Cr<=80 micromol/L: eGFR = (141 + 22 if black) x (Cr/0.9)^-0.411 x 0.993^age

    Males with Cr<=80 micromol/L: eGFR = (141 + 22 if black) x (Cr/0.9)^-1.209 x 0.993^age

    Where Cr is creatinine in micromol/L and age is age in years. The correction for “black” race, based on US data, is not applied to any patients.

    Urea reduction ratio / Kt/V

    Results are requested in one of these formats, using the stop flow method on a mid-week dialysis. Single pool Kt/V is collected, along with the method used. For conversion of URR to Kt/V urea the formula used(2) is Kt/V = 0.023 * PRU – 0.284 (note that PRU = percent reduction in urea and not URR).

    Body mass index

    Body mass index (BMI) is calculated as weight (kg) / (height (m))2. The categories used are: underweight <20 kg/m2, normal 20-24.9 kg/m2, overweight 25-29.9 kg/m2,
    obese >=30 kg/m2.

    Peritoneal dialysis measures

    These are the standard measures, often calculated by computerised patient management programs(3).

    Residual renal function

    The measure used is the arithmetic mean of urea and creatinine clearance from a 24-hour urine collection and serum creatinine and urea.

    Peritoneal equilibration test

    The ratio of dialysate to plasma glucose is used, following a 4 hour dwell of a 2 litre 2.5% bag of dialysate, performed within 6 months after initiation of peritoneal dialysis.

  • Rates and Measures

    Incidence rates

    Except where otherwise stated, quoted incidence rates are per calendar year, and are expressed per million population.

    Prevalence rates

    Except where otherwise specified, prevalence rates are point prevalence rates at 31st December.

    Population denominator

    All populations used in the annual report were stratified by age and sex.

    Australian populations were taken from the Australian Bureau of Statistics (ABS) and New Zealand populations were taken from Statistics New Zealand (SNZ).

    All estimated and projected  populations used for Australia and New Zealand were for 30 June of each year, and all websites were accessed 23 September 2014 for analysis of annual 2013 locked dataset.

    Estimated population data for each Australian state and territory came from ABS 3101.0 series(4).

    Projected population data for each Australian state and territory came from ABS 3222.0 series(5).

    Population data for Indigenous Australians were taken from ABS 3238.0(6), using series A (the most conservative estimates) for populations after 1996.

    Populations serviced by the Greater Southern Area Health Service were estimated by the South Eastern Region of NSW. These estimates were taken from ABS 3235.0(7)

    All New Zealand population estimates were taken from Statistics NZ Infoshare(8) and projected population were taken from NZ. Stat’s(9). Maori populations were  taken from NZ Infoshare Maori population estimates(10).

    Estimates of resident Pacific People populations after were taken from NZ Stats(11) for years 2006 onwards. Prior to this, populations of Pacific people before 2006 were only available for years  1996, 2001 (and 2006), and we used linear interpolation to estimate populations for each age and sex group for the years 1997-2001 and 2002-2005.

    Death Population Data:
    All Australian death data were taken from ABS 3302.0 series(12). Death data is not available for publications by age and sex on ABS website for some states. Overall data by states and territory is used. New Zealand death data were taken from NZ Infoshare(13).

    Survival rates

    For transplant recipients, survival rates exclude those who were transplanted overseas or were recipients of multiple organ grafts.

    Graft survival (unless otherwise qualified) includes both cessation of graft function
    (ie return to dialysis) and patient death.

    Rates for patient survival for fixed periods for transplantation are calculated according to the life-table method and thus include an adjustment to the risk-set of ½ of those censored without failure over the interval to create an “average” risk set.

    Graft survival

    For outcomes of kidney transplants, graft failure includes both loss of graft function (i.e. return to dialysis) and death of patients (with graft function). Calculations of patient survival for transplant recipients includes all subsequent modalities (i.e. deaths after graft failure are included). Patients transplanted overseas are excluded from calculations.

    Dialysis Survival

    Patient and technique survivals for haemodialysis and peritoneal dialysis are based on the dialysis modality at 90 days after first treatment for patients not transplanted during that period. Patients are followed up until they are either transplanted (at which point they are censored) or until they have a ‘permanent’ change of dialysis modality or until death or most recent follow up date. A ‘permanent’ change of dialysis is defined as any change in excess of 30 days.

    Peritonitis survivals are calculated from first peritoneal dialysis (ignoring all earlier treatments) to date of first peritonitis episode. If there were no episodes of peritonitis then calculation is censored at change of treatment from peritoneal dialysis to haemodialysis or transplantation. Peritoneal dialysis includes automated peritoneal and continuous ambulatory peritoneal dialysis. Excluded are patients who had peritonitis before commencing peritoneal dialysis.

    Death and other event rates

    Rates are expressed per 100 person years at risk (unless otherwise stated). Some analyses include survival of all patients, others exclude the first 90 days of follow up. This is stated in the individual analyses.

    Age standardisation

    All rates are crude, not age-standardised. The age distribution of the populations for Australia and New Zealand can be obtained by contacting the Registry.

    Peritonitis rates

    Peritonitis rates are present using episodes of peritonitis reported during periods of peritoneal dialysis – episodes reported prior to commencement of peritoneal dialysis (for example between Tenckhoff catheter insertion and commencement of peritoneal dialysis) are not included in these calculations.

  • Database

    Data is stored on a relational database using Microsoft SQL Server 2012.

  • Statistics

    Statistical analyses were performed using Stata version 14.

  • References

    1. Levey AS, Stevens LA, Schmid CH, Zhang YL, Castro AF, Feldman HI, et al. A new equation to estimate glomerular filtration rate. Ann Intern Med. 2009 May 5; 150(9):604-612.
    2. Basile C, Casino F, Lopez T: Percent reduction in blood urea concentration during dialysis estimates Kt/V in a simple and accurate way. Am J Kidney Dis 1990:15; 40-45.
    3. Zasadny KR, Wahl RL: Standardized uptake values of normal tissues at PET with 2‑[fluorine‑18]‑fluoro-2-deoxy-D-glucose: variation with body weight and method for correction. Radiology 1993: 189; 847-850.
    4. http://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/3101.0Mar%202014?OpenDocument
    5. http://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/3222.02012%20(base)%20to%202101?OpenDocument
    6. http://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/3238.02001%20to%202026?OpenDocument
    7. http://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/3235.02013?OpenDocument
    8. http://www.stats.govt.nz/infoshare/SelectVariables.aspx?pxID=3e317ac0-5674-4037-99a5-45121873f289
    9. http://nzdotstat.stats.govt.nz/wbos/Index.aspx
    10. http://www.stats.govt.nz/browse_for_stats/population/estimates_and_projections/MaoriPopulationEstimates_HOTPAtJun14.aspx
    11. http://nzdotstat.stats.govt.nz/wbos/Index.aspx
    12. http://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/3302.02013?OpenDocument
    13. http://www.stats.govt.nz/infoshare/SelectVariables.aspx?pxID=9f25b908-80cc-439c-a39f-6711da92fcc2