The absence of a positive family history (PFH) in 10%-25% of patients poses a diagnostic challenge for autosomal dominant polycystic kidney disease (ADPKD). In the Toronto Genetic Epidemiology Study of Polycystic Kidney Disease, 210 affected probands underwent renal function testing, abdominal imaging, and comprehensive and mutation screening. From this cohort, we reviewed all patients with and without an apparent family history, examined their parental medical records, and performed renal imaging in all available parents of unknown disease status. Subsequent reclassification of 209 analyzed patients revealed 72.2% (151 of 209) with a PFH, 15.3% (32 of 209) with disease, 10.5% (22 of 209) with an indeterminate family history, and 1.9% (four of 209) with PFH in retrospect. Among the patients with cases, we found two families with germline mosaicism and one family with somatic mosaicism. Additionally, analysis of renal imaging revealed that 16.3% (34 of 209) of patients displayed atypical PKD, most of which followed one of three patterns: asymmetric or focal PKD with PFH and an identified or mutation (15 of 34), asymmetric and PKD with proven or suspected somatic mosaicism (seven of 34), or focal PKD without any identifiable or mutation (eight of 34). In conclusion, PKD without an apparent family history may be due to disease, missing parental medical records, germline or somatic mosaicism, or mild disease from hypomorphic and mutations. Furthermore, mutations of a newly identified gene for ADPKD, , and somatic mosaicism need to be considered in the mutation-negative patients with focal disease.

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Background:International Classification of Diseases, 10th Revision codes (ICD-10) for autosomal dominant polycystic kidney disease (ADPKD) is used within several administrative health care databases. It is unknown whether these codes identify patients who meet strict clinical criteria for ADPKD.Objective:The objective of this study is (1) to determine whether different ICD-10 coding algorithms identify adult patients who meet strict clinical criteria for ADPKD as assessed through medical chart review and (2) to assess the number of patients identified with different ADPKD coding algorithms in Ontario.Design:Validation study of health care database codes, and prevalence.Setting:Ontario, Canada.Patients:For the chart review, 201 adult patients with hospital encounters between April 1, 2002, and March 31, 2014, assigned either ICD-10 codes Q61.2 or Q61.3.Measurements:This study measured positive predictive value of the ICD-10 coding algorithms and the number of Ontarians identified with different coding algorithms.Methods:We manually reviewed a random sample of medical charts in London, Ontario, Canada, and determined whether or not ADPKD was present according to strict clinical criteria.Results:The presence of either ICD-10 code Q61.2 or Q61.3 in a hospital encounter had a positive predictive value of 85% (95% confidence interval [CI], 79%-89%) and identified 2981 Ontarians (0.02% of the Ontario adult population). The presence of ICD-10 code Q61.2 in a hospital encounter had a positive predictive value of 97% (95% CI, 86%-100%) and identified 394 adults in Ontario (0.003% of the Ontario adult population).Limitations:(1) We could not calculate other measures of validity; (2) the coding algorithms do not identify patients without hospital encounters; and (3) coding practices may differ between hospitals.Conclusions:Most patients with ICD-10 code Q61.2 or Q61.3 assigned during their hospital encounters have ADPKD according to the clinical criteria. These codes can be used to assemble cohorts of adult patients with ADPKD and hospital encounters.

Background The ability to identify patients with autosomal dominant polycystic kidney disease (ADPKD) and distinguish them from patients with similar conditions in healthcare administrative databases is uncertain. We aimed to measure the sensitivity and specificity of different ADPKD administrative coding algorithms in a clinic population with non-ADPKD and ADPKD kidney cystic disease. Methods We used a dataset of all patients who attended a hereditary kidney disease clinic in Toronto, Ontario, Canada between 1 January 2010 and 23 December 2014. This dataset included patients who met our reference standard definition of ADPKD or other cystic kidney disease. We linked this dataset to healthcare databases in Ontario. We developed eight algorithms to identify ADPKD using the International Classification of Diseases, 10th Revision (ICD-10) codes and provincial diagnostic billing codes. A patient was considered algorithm positive if any one of the codes in the algorithm appeared at least once between 1 April 2002 and 31 March 2015. Results The ICD-10 coding algorithm had a sensitivity of 33.7% [95% confidence interval (CI) 30.0–37.7] and a specificity of 86.2% (95% CI 75.7–92.5) for the identification of ADPKD. The provincial diagnostic billing code had a sensitivity of 91.1% (95% CI 88.5–93.1) and a specificity of 10.8% (95% CI 5.3–20.6). Conclusions ICD-10 coding may be useful to identify patients with a high chance of having ADPKD but fail to identify many patients with ADPKD. Provincial diagnosis billing codes identified most patients with ADPKD and also with other types of cystic kidney disease.

Background: It is uncertain how often patients with autosomal dominant polycystic kidney disease (ADPKD) develop kidney stones. Objective: To review English-language studies reporting the incidence and prevalence of stones and stone interventions in adults with ADPKD. Design: Systematic review and meta-analysis. Setting: Any country of origin. Patients: Adult patients with ADPKD. Measurements: Incidence or prevalence of kidney stones and stone interventions. Methods: We reviewed 1812 citations from bibliographic databases, abstracted data from 49 eligible studies, and assessed methodological quality in duplicate. In some studies, the proportion of adults with ADPKD with the outcome were compared to adults without ADPKD; for these studies, prevalence risk ratios were calculated and pooled using a random effects model. Results: We identified 49 articles that met our review criteria. The methodological quality of many studies was limited (scores ranging from 2 to 14 out of 22, with a higher score indicating higher quality). No study clearly reported stone incidence, and in the cross-sectional studies, the definition of stones was often unclear. The prevalence of stones ranged from 3% to 59%, and a prevalence of stone interventions ranged from 1% to 8%; the average patient age at the time of assessment ranged from 26 to 61 years across the studies. Two studies reported a nonstatistically significant higher stone prevalence in patients with ADPKD compared to unaffected family members. Compared to unaffected family members, patients with ADPKD had a higher prevalence of kidney stones (6 cross-sectional studies; unadjusted prevalence ratio: 1.8; 95% confidence interval: 1.3 to 2.6; P = .0007; test for heterogeneity: I2 = 0%, P = .8). Limitations: Studies were limited to articles published in English. Conclusions: The prevalence of kidney stones and stone interventions in adults with ADPKD remains uncertain. Future studies of higher methodological quality are needed to better characterize the incidence and prevalence of kidney stones in patients with ADPKD. Trial registration: We did not register the protocol for this systematic review.

Purpose of review:Genetic testing can improve diagnostic precision in some patients with end-stage renal disease (ESRD) providing the potential for targeted therapy and improved patient outcomes. We sought to describe the genetic architecture of ESRD and Canadian data sources available for further genetic investigation into ESRD.Sources of information:We performed PubMed searches of English, peer-reviewed articles using keywords “chronic kidney disease,” “ESRD,” “genetics,” “sequencing,” and “administrative databases,” and searched for nephrology-related Mendelian diseases on the Online Mendelian Inheritance in Man database.Methods:In this narrative review, we discuss our evolving understanding of the genetic architecture of kidney disease and ESRD, the risks and benefits of using genetic data to help diagnose and manage patients with ESRD, existing public Canadian biobanks and databases, and a vision for future genetic studies of ESRD in Canada.Key findings:ESRD has a polygenic architecture including rare Mendelian mutations and common small effect genetic polymorphism contributors. Genetic testing will improve diagnostic accuracy and contribute to a precision medicine approach in nephrology. However, the risk and benefits of genetic testing needs to be considered from an individual and societal perspective, and further research is required. Merging existing health data, linking biobanks and administrative databases, and forming Canadian collaborations hold great potential for genetic research into ESRD. Large sample sizes are necessary to perform the suitably powered investigations required to bring this vision to reality.Limitations:This is a narrative review of the literature discussing future directions and opportunities. It reflects the views and academic biases of the authors.Implications:National collaborations will be required to obtain sample sizes required for impactful, robust research. Merging established datasets may be one approach to obtain adequate samples. Patient education and engagement will improve the value of knowledge gained.

Background: There is a perception that patients with autosomal dominant polycystic kidney disease (ADPKD) are more likely to develop kidney stones than the general population. Objective: To compare the rate of hospital encounter with kidney stones and the rate of stone interventions between patients with and without ADPKD. Design: Retrospective cohort study. Setting: Ontario, Canada. Patients: Patients with and without ADPKD who had a prior hospital encounter between 2002 and 2016. Measurements: Rate of hospital encounter with kidney stones and rate of stone intervention. Methods: We used inverse probability exposure weighting based on propensity scores to balance baseline indicators of health between patients with and without ADPKD. We followed each patient until death, emigration, outcomes, or March 31, 2017. We used a Cox proportional hazards model to compare event rates between the two groups. Results: Patients with ADPKD were at higher risk of hospital encounter with stones compared with patients without ADPKD (81 patients of 2094 with ADPKD [3.8%] vs 60 patients of 1902 without ADPKD [3.2%]; 8.9 vs 5.1 events per 1000 person-years; hazard ratio 1.6 [95% CI, 1.3-2.1]). ADPKD was not associated with a higher risk of stone intervention (49 of 2094 [2.3%] vs 47 of 1902 [2.4%]; 5.3 vs 3.9 events per 1000 person-years; hazard ratio 1.2 [95% CI = 0.9-1.3]). Limitations: We did not have information on kidney stone events outside of the hospital. There is a possibility of residual confounding. Conclusion: ADPKD was a significant risk factor for hospital encounters with kidney stones.

Background:Patients with diabetes and chronic kidney disease (CKD) are at high risk of diabetes-related complications. Diabetes care can support these individuals, but outpatient clinic appointments can be difficult to attend, given their already high burden of multimorbidity.Methods:We systematically searched the medical and grey literature for studies that evaluated the effect of nonconventional diabetes care strategies on diabetes-related outcomes in adults with stages 2–5 CKD or using dialysis (end of search December 30, 2017). We included both randomized-controlled trials and observational studies. Study selection and data extraction were completed by two independent reviewers. Diabetes-related outcomes included glycemic, blood pressure, and lipid control, along with microvascular complications, macrovascular complications, and death.Results:After screening 2177 relevant citations, we identified 34 studies which met inclusion. The majority were observational studies. Studies were frequently small, single-centered, and excluded patients with more advanced CKD. Nonconventional diabetes care strategies included community-based care, unique self-management and education programs, nurse-led care clinics, dialysis-based diabetes programs, telemedicine, and interdisciplinary care clinics. Programs were most often developed by study investigators. Although there were limitations to several of the included studies, programs were described to have modest effects on physiologic outcomes, and in some cases, diabetes-related complications and death.Conclusions:Nonconventional diabetes-related care might be helpful to patients with CKD. Prior to developing and implementing programs, however, it will be important to study them more rigorously, understand their acceptability to patients, and evaluate their costs and feasibility in a real-world setting.