GUIDELINE 3. INDIVIDUALS AT INCREASED RISK OF CHRONIC KIDNEY DISEASE
Some individuals without kidney damage and with normal or elevated GFR are at increased risk for development of chronic kidney disease.
- All individuals should be assessed, as part of routine health encounters, to determine whether they are at increased risk of developing chronic kidney disease, based on clinical and sociodemographic factors.
- Individuals at increased risk of developing chronic kidney disease should undergo testing for markers of kidney damage, and to estimate the level of GFR.
- Individuals found to have chronic kidney disease should be evaluated and treated as specified in Guideline 2.
- Individuals at increased risk, but found not to have chronic kidney disease, should be advised to follow a program of risk factor reduction, if appropriate, and undergo repeat periodic evaluation.
Epidemiological studies show an increased risk for chronic kidney disease, especially kidney failure, among individuals with certain clinical and sociodemographic characteristics. This suggests that there are risk factors for chronic kidney disease. In principle, prevention of adverse outcomes of chronic kidney disease could be facilitated by evaluating individuals with risk factors, to enable earlier detection, and by risk factor reduction in individuals without chronic kidney disease, to prevent or slow the development of chronic kidney disease.
Definition of Risk Factors (R)
A risk factor is defined as an attribute that is associated with increased risk of an outcome. In principle, the relationship between the risk factor and the outcome may be either causal or non-causal. Causal risk factors are determinants of the outcome, and successful intervention to reduce exposure to them would improve outcomes. Non-causal risk factors may be associated with the outcome through confounding or reverse causation. Interventions to reduce exposure to non-causal risk factors would not necessarily improve outcomes.
Classification of risk factors (R). A useful classification of risk factors has been used in cardiovascular disease epidemiology100 and is shown in Table 38.
Risk factors for chronic kidney disease (R, O). In principle, risk factors for development of chronic kidney disease would include susceptibility factors and initiation factors. In addition, because it can be difficult to detect the onset of chronic kidney disease, some risk factors for faster progression may appear to be to susceptibility or initiation factors (Table 39).
Note that progression factors may be associated with progression either because initial damage cannot be resolved or because damage is ongoing.
In addition, numerous factors have been shown to be associated with worse outcomes in patients with kidney failure, (such as inadequate dialysis dose, temporary vascular access, anemia, and low serum albumin concentration). These “end-stage” factors have been discussed in previous KDOQI guidelines and are not relevant for this discussion.
Textbooks and reviews list a large number of potential risk factors for chronic kidney disease. The difficulty of detecting the early stages of chronic kidney disease makes it difficult to determine whether the risk factors so far identified relate more to susceptibility, initiation, or progression.
Table 40 contains a partial list of clinical and sociodemographic factors that have been implicated as susceptibility or initiation factors. Progression factors are discussed in more detail in Guideline 13.
Table 41 shows relationships between types of chronic kidney disease and CKD risk factors. For some of these factors (for example, diabetes), interventions (like strict glycemic control) have been proven to lower the risk of developing chronic kidney disease (Category I, Table 38). For other factors (for example, hypertension), interventions (like antihypertensive therapy) are likely to lower the risk of chronic kidney disease (Category II, Table 38). For other factors (for example, autoimmune diseases), modification of immune responses might lower the risk chronic kidney disease (Category III, Table 38). A number of these factors (for example, family history, age, race and ethnicity) are not modifiable (Category IV, Table 38).
Prevalence of individuals with risk factors for chronic kidney disease (R). The prevalence of individuals at increased risk for development of chronic kidney disease has not been studied systematically. However, some idea of the magnitude of the problem can be obtained by reviewing data from recent publications (Table 42).
This guideline provides a conceptual framework to the definition, detection, and evaluation of individuals at increased risk of chronic kidney disease, but does not provide sufficient details to guide health care providers in screening individuals or developing screening programs. It is beyond the scope of these guidelines to provide specific instructions for screening.
Universal screening for chronic kidney disease is recommended for children in the United States, but not for adults. However, the list of individuals at increased risk for chronic kidney disease includes a large fraction of the adult population (Table 42). Thus, it is important to carefully consider the definition of individuals at increased risk and methods for testing them. Suggestions (based on opinion) for evaluation of individuals at increased risk for chronic kidney disease are provided in Part 9.
Implementation of these guidelines will require education of all health care providers about risk factors for chronic kidney disease and methods of testing. The Sixth Report of the Joint National Committee for the Prevention, Evaluation, Detection and Treatment of High Blood Pressure (JNC-VI) and the American Diabetes Association have issued recommendations for the evaluation of patients with high blood pressure and diabetes, respectively, for chronic kidney disease. However, as indicated in Table 42, a large number of individuals without high blood pressure and diabetes may also be at increased risk. Thus, it will be important to test a larger population than currently targeted, which would increase the cost of health care.
The increased health care costs that would follow implementation of a screening program for chronic kidney disease may well require a more solid base of evidence than is currently available. The Work Group recommends development of a clinical practice guideline focused on this issue in order to develop specific recommendations for evaluating adults for chronic kidney disease. In the past, universal screening was not recommended because of the low prevalence of chronic kidney disease and the lack of treatments to improve outcomes. Data provided in these guidelines suggests that the prevalence of earlier stages of chronic kidney disease is higher than previously known and that earlier detection and treatment to prevent or delay the loss of kidney function and development of cardiovascular disease in chronic kidney disease. If sufficient information is not available to assess the value of testing individuals at increased risk, or of universal screening, the Work Group suggests that research on evaluation programs should be conducted.