Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited CKD, accounting for approximately 10% of kidney failure before age 65. ADPKD is characterized by the gradual enlargement of innumerable cysts, which progressively compromise kidney function. ESKD typically occurs in the sixth decade of life, and patients with ADPKD also suffer from significant liver cysts, hypertension, kidney stones, painful cyst ruptures, and intracranial aneurysms. Early ADPKD may be asymptomatic, but individuals are often aware of their risk because of an affected parent. Awareness leads to asymptomatic screening, which may result in earlier diagnosis. Early diagnosis creates opportunities for kidney-focused preventive care, such as intensive blood pressure management, inhibition of the renin-angiotensin-aldosterone system, and implementation of approved therapies for individuals at high risk for progression to ESKD (i.e., vasopressin V2 antagonists).
In this issue of Kidney 360, Aung et al. perform a descriptive cross-sectional analysis of the prevalence of diagnosed ADPKD among patients belonging to Kaiser Permanente Southern California (KPSC), an integrated care system. The authors identified 3868 individuals among 9,071,375 members with a diagnosis of ADPKD, using diagnostic codes extracted from the electronic health records enrolled between 2002 and 2018. The authors then evaluated patient age, sex, level of office blood pressure control, body mass index, and overall health care exposures. These analyses were performed, including patient self-identified race. In so doing, they provided a pragmatic “snapshot” of the health experiences of patients who were insured and had known ADPKD.
Their findings showed that, although the prevalence of ADPKD diagnosis varied by race, the prevalence of diagnosed ADPKD was substantially lower in all groups than the estimated prevalence of PKD mutations, suggesting that within the KPSC patient population, there are affected ADPKD individuals not yet diagnosed, and possibly patients with ADPKD who died before a diagnosis was made. In the first group, there are missed opportunities for early, life-prolonging medical management. In the latter group, there may be patients who suffered from ADPKD-specific complications, for example, an intracranial aneurysm rupture. Patient characteristics differed by race, with the highest prevalence of nearly every comorbid condition, including complications specific to ADPKD, among Black patients. Use of antihypertensive medications and utilization of clinic, emergency department, and hospital all varied substantially by race. So, although ADPKD is a Mendelian disorder, without a particular racial predilection, disparities in health care appear to be present, as with other kidney diseases.
The interpretation of these findings should be made in the context of several issues, which are acknowledged by the authors. The use of EHR codes obscures the actual criteria by which patients were diagnosed, whether by imaging, known personal or family history at the time of enrollment, or clinically apparent CKD. ADPKD may be diagnosed incidentally, on imaging performed for other purposes, and such patients may have low short-term mortality. Such patients could accumulate over an extended observation period, leading to increased prevalence over time, as observed by the authors, without necessarily reflecting any changes in disease prevalence or increased detection. Also undetermined is the effect on the demographic and socioeconomic patient-mix of KPSC during Medicaid expansion due to the Affordable Care Act, which occurred in the middle of the study period.
These findings, in combination with what is already published, indicate that patients with known ADPKD represent only a small fraction of the prevalence of this disease, and suggest efforts to improve outcomes will depend on increased screening and detection of patients who are undiagnosed and early stage. The KPSC dataset provides a real-world depiction of ADPKD, with representation of multiple ethnic groups, but further work is needed to determine whether findings in this California cohort are generalizable to economic and social conditions experienced in other parts of the county.
Disclosures
All authors have nothing to disclose.
Funding
None.
Acknowledgments
The content of this article reflects the personal experience and views of the author(s) and should not be considered medical advice or recommendation. The content does not reflect the views or opinions of the American Society of Nephrology (ASN) or Kidney360. Responsibility for the information and views expressed herein lies entirely with the author(s).
Footnotes
See related article, “Autosomal Dominant Polycystic Kidney Disease Prevalence among a Racially Diverse United States Population, 2002 through 2018,” on pages 2010–2015.
Author Contributions
A. Chapman and R. McGill conceptualized the study and wrote the original draft.