Message from the new Chairman of the Registry, Carmine Zoccali
The ERA-EDTA Registry, now a forty years old enterprise, was the first initiative worldwide that collected demographic and clinical data on patients with end stage renal disease. The Registry has always been and remains a valuable instrument to monitor the population on renal replacement therapy in Europe. However modern nephrology has new challenges that demand a more articulated mission. While progress in basic and clinical science now goes at an unprecedented speed, the public health benefits deriving from the application of available scientific knowledge to the treatment of patients with chronic renal diseases lags far behind. Treatment goals are very often unmet in dialysis patients, particularly so in those with cardiovascular complications. There has been a blossoming of clinical practice guidelines. Yet the “guidelines era” is still in the infancy years and adherence to guidelines recommendations is much unsatisfactory. In this context providing systematic information on clinical performance measures across Europe represents a priority if we are to establish a useful source of information on clinical practice and to set achievable health objectives for the population of patients with end stage renal disease. It is the ambition of the Registry to provide European investigators new opportunities for research on a wide scale. In this perspective we will start new research projects in various areas and we will make a special effort to establish national sera and DNA banks linked to high quality clinical data bases. We would like to stimulate interest on clinical epidemiology of chronic renal diseases. To this end the Registry will promote short educational courses on Epidemiology and Biostatistics in European countries and each issue of this newsletter will include brief introductory notes in Epidemiology and Biostatistics.
This newsletter will be instrumental to make transparent the activity of the Registry committee and to reach the largest possible number of nephrologists. We have ahead difficult challenges but are confident that with the support of the ERA-EDTA and of European nephrologists the Registry will gradually meet the goals of its new mission.
QUality European STudy – a project in preparation
Many studies have been done to improve the outcome of patients on renal replacement therapy. Both the results of those studies and the opinion of experts in particular fields of nephrology have provided the basis for the European Best Practice Guidelines, the NKF K-DOQI guidelines and guidelines created and issued by National Societies of Nephrology.
Such guidelines can be considered as one of the many different ways to improve and assure the quality of patient care. Currently however, information is lacking on if and how these guidelines are disseminated and used in the different countries in Europe and what other initiatives with regard to quality assurance have been taken by the National Societies. Also National and Regional Registries can play an important role in this process of quality assurance depending on the amount of clinical data that they collect from individual patients.The ERA-EDTA Registry is preparing a project to list the quality assurance initiatives at a national level and to see which parties are involved in these initiatives and how. For a start we intend to do this by means of two surveys, one aimed at the National Societies and another aimed at National and Regional Registries, the parties whose role is expected to be crucial in the quality assurance process. We hope that the experience gained in some countries will provide the others with ideas and tools on how to organize their own quality assurance systems and adapt them to their own needs and circumstances.
Introductory notes in Epidemiology and Biostatistics
Risks and number needed to treat: definitions and interpretation
Epidemiological papers often report risks to assess the onset of disease, death or other health outcomes. Absolute risk is a measure of disease frequency and can be defined as the number of subjects developing the disease (or other health outcome) during a time period divided by the number of subjects followed for the time period. It is a probability with a value ranging from zero to one. In the medical literature risk is very often expressed as relative risk (RR), which is defined by the risk for one group (mostly the exposed group) divided by the risk for another group (mostly the unexposed group). This RR measures the increased (or decreased) risk of disease associated with exposure to the factor of interest. An RR of 1 indicates that the risk is the same in the exposed and the unexposed group. An RR greater than 1 indicates that there is an increased risk and an RR less than one indicates a reduction in risk in the exposed group, compared with the unexposed group. Suppose the RR for the exposed group is calculated to be 0.75, then it is said that patients have a risk reduction of 25% compared to the unexposed group. Relative risks, however, must be interpreted in the light of absolute risks.
Let's give an example derived from the ERA-EDTA Registry data. Patients receiving pre-emptive transplants have an adjusted relative risk of 0.71 and therefore a 29% lower risk of death compared to patients receiving transplants while on dialysis. This 29% risk reduction seems impressive. However, the absolute risk of death within 5 years in patients who receive transplants while on dialysis is 15 out of 100, whereas 9 out of 100 patients who receive pre-emptive transplants will die. This seems somewhat less impressive. Confusion caused by relative risks can be avoided by the simultaneous presentation of the absolute risks or by calculating the number needed to treat (NNT) to save one life. The NNT is the reciprocal of the risk difference between the two groups. In this case the reciprocal of 15 minus 9 divided by 100 is 17, meaning that 17 patients need to receive a pre-emptive transplant before one patient benefits at 5 years.
Kitty Jager, ERA-EDTA Registry Managing Director