Abbreviation: CKD=chronic kidney disease.

1. In asymptomatic adults without known chronic kidney disease (CKD),* what are the effects of screening for CKD vs. no screening on clinical outcomes?
1a. What are the effects of repeat vs. one-time screening for CKD or repeat screening at different intervals?
2. What are the harms of screening for CKD vs. no screening?
3. What is the diagnostic accuracy of screening to identify adults with CKD stages 1–3?
4. How does diagnostic accuracy vary in populations defined by race, ethnicity, age, and sex?
5. Among adults with screen-detected CKD or CKD stages 1–3,^† what are the effects of monitoring for worsening kidney function, kidney damage, or both vs. no monitoring on clinical outcomes?
6. Among adults with screen-detected CKD or CKD stages 1–3,^† what are the harms of monitoring for worsening kidney function, kidney damage, or both vs. no monitoring?
7. Among adults with screen-detected CKD or CKD stages 1–3,^† what are the effects of treatment on likelihood of developing stage 4 or 5 CKD?
8. Among adults with screen-detected CKD or CKD stages 1–3,^† what are the effects of treatment on clinical outcomes?
9. Among adults with screen-detected CKD or CKD stages 1–3,^† what are the effects of treatment on harms?

*For screening, studies in which patients were selected on the basis of having conditions associated with CKD (e.g., hypertension or diabetes) are not eligible for inclusion. However, studies are not required to exclude patients with these conditions. 
^†For treatment, studies will not be restricted according to whether patients have screen- or nonscreen-detected CKD, or whether patients are eligible for evaluated treatments for reasons other than CKD (e.g., presence of diabetes mellitus, hypertension, or dyslipidemia).

Contextual questions will not be systematically reviewed and are not shown in the Analytic Framework.

1. What disparities are present in diagnosis of CKD and utilization of treatment, and what factors are associated with disparities?
2. What is the effectiveness of interventions aimed at reducing disparities in persons with CKD?
3. What are the harms of being labeled with a diagnosis of CKD stages 1–3?

To the extent possible, we plan to describe the participant characteristics and major intervention components of the included studies. Data on population characteristics will help us explore the degree to which the findings are broadly representative of the U.S. population, including individuals across age; sex and gender; racial, ethnic, and cultural identity; socioeconomic status; and geographic region. Evidence will be evaluated to determine if there are common components of efficacious interventions (e.g., diet approaches or medication dose) and, to the extent possible, whether interventions tailored to specific groups tend to have larger effect sizes than those that are not tailored. As part of our effort to address health equity, we will search for and highlight interventions that demonstrate effectiveness in groups of individuals who historically have lower rates of screening and in traditionally stigmatized or underrepresented groups. Additionally, the proposed contextual questions are designed to address other important health equity considerations.

The Research Approach identifies the study characteristics and criteria that the Evidence-based Practice Center will use to search for publications and to determine whether identified studies should be included or excluded from the Evidence Review. Criteria are overarching as well as specific to each of the Key Questions.

*Will evaluate how outcomes vary according to age.
^†Definitions of CKD:

KDOQI, 2002: Kidney damage for ≥3 months, as defined by structural or functional abnormalities of the kidney, with or without decreased GFR, manifest by either: pathological abnormalities or markers of kidney damage, including abnormalities in the composition of the blood or urine, or abnormalities in imaging tests and/or GFR <60 mL/min/1.73 m² for ≥3 months.¹

KDIGO, 2012: Either of the following present for >3 months: markers of kidney damage (one or more), including albuminuria (albumin excretion rate ≥30 mg/24 hours; albumin to creatinine ratio ≥30 mg/g [≥3 mg/mmol]), urine sediment abnormalities, electrolyte and other abnormalities due to tubular disorders, abnormalities detected by histology, structural abnormalities detected by imaging, or history of kidney transplantation and/or decreased GFR (GFR <60 mL/min/1.73 m²; GFR categories G3a-G5).²  

Abbreviations: CKD=chronic kidney disease; GFR=glomerular filtration rate; KDIGO=Kidney Disease Improving Global Outcomes; KDOQI=Kidney Disease Outcomes Quality Initiative.

The draft Research Plan was posted for public comment on the USPSTF website from January 19, 2023, to February 15, 2023. In response to public comment, the Research Plan was revised to clarify that the population for key questions on treatment was persons with screen-detected or CKD stages 1–3 (not necessarily screen-detected). Other changes included the addition of a sub-key question on the effectiveness of repeat screening for CKD or different CKD screening intervals, the addition of thiazide and thiazide-like diuretics as CKD interventions, and the addition of a footnote to clarify that the analysis will evaluate how outcomes vary by age. Although comments suggested expanding the screening population to those with diabetes mellitus and hypertension, this was deemed out of scope for the USPSTF because evaluation of kidney disease is part of disease management of these conditions. Guidelines on evaluation of kidney disease in persons with diabetes mellitus and hypertension already exist. Some comments suggested expansion of the treatment population to persons with later-stage CKD (CKD stages 4 and 5); however, the treatment population remained focused on earlier-stage CKD (stages 1–3). Earlier-stage CKD is more applicable to screening in primary care because it is more likely to be asymptomatic and managed in primary care; in addition, CKD stage 4 is uncommon and CKD stage 5 represents end-stage renal disease, often requiring renal replacement.