Progression of autosomal dominant kidney disease: measurement of the stage transitions of chronic kidney disease

Mortality risk in patients with autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the leading inheritable cause of end-stage renal disease (ESRD). Mortality data specific to patients with ADPKD is currently lacking; thus, the aim of this study was to estimate mortality in patients with ADPKD.

METHODS

We analyzed data from the United States Renal Data System (USRDS) for patients with ADPKD available during the study period of 01/01/2014-12/31/2016, which included a cohort of patients with non-ESRD chronic kidney disease (CKD) and a cohort of patients with ESRD. Mortality rates with 95% confidence intervals (CIs) were calculated overall and by age group, sex, and race for the full dataset and for a subset of patients aged ≥ 65 years. Adjusted mortality hazard ratios (HRs) were calculated using Cox regression modeling by age group, sex, race, and CKD stage (i.e., non-ESRD CKD stages 1-5) or ESRD treatment (i.e., dialysis and transplant).

RESULTS

A total of 1,936 patients with ADPKD and non-ESRD CKD and 37,461 patients with ADPKD and ESRD were included in the analysis. Age-adjusted mortality was 18.4 deaths per 1,000 patient-years in the non-ESRD CKD cohort and 37.4 deaths per 1,000 patient-years in the ESRD cohort. As expected, among the non-ESRD CKD cohort, patients in CKD stages 4 and 5 had a higher risk of death than patients in stage 3 (HR = 1.59 for stage 4 and HR = 2.71 for stage 5). Among the ESRD cohort, patients receiving dialysis were more likely to experience death than patients who received transplant (HR = 2.36). Age-adjusted mortality among patients aged ≥ 65 years in the non-ESRD CKD cohort was highest for Black patients (82.7 deaths per 1,000 patient-years), whereas age-adjusted mortality among patients aged ≥ 65 years in the ESRD cohort was highest for White patients (136.1 deaths per 1,000 patient-years).

CONCLUSIONS

Mortality rates specific to patients aged ≥ 65 years suggest racial differences in mortality among these patients in both non-ESRD CKD and ESRD cohorts. These data fill an important knowledge gap in mortality estimates for patients with ADPKD in the United States.

A Computable Phenotype for Autosomal Dominant Polycystic Kidney Disease

Background

A computable phenotype is an algorithm used to identify a group of patients within an electronic medical record system. Developing a computable phenotype that can accurately identify patients with autosomal dominant polycystic kidney disease (ADPKD) will assist researchers in defining patients eligible to participate in clinical trials and other studies. Our objective was to assess the accuracy of a computable phenotype using International Classification of Diseases 9th and 10th revision (ICD-9/10) codes to identify patients with ADPKD.

Methods

We reviewed four random samples of approximately 250 patients on the basis of ICD-9/10 codes from the EHR from the Kansas University Medical Center database: patients followed in nephrology clinics who had ICD-9/10 codes for ADPKD (Neph+), patients seen in nephrology clinics without ICD codes for ADPKD (Neph-), patients who were not followed in nephrology clinics with ICD codes for ADPKD (No Neph+), and patients not seen in nephrology clinics without ICD codes for ADPKD (No Neph-). We reviewed the charts and determined ADPKD status on the basis of internationally accepted diagnostic criteria for ADPKD.

Results

The computable phenotype to identify patients with ADPKD who attended nephrology clinics has a sensitivity of 99% (95% confidence interval [95% CI], 96.4 to 99.7) and a specificity of 84% (95% CI, 79.5 to 88.1). For those who did not attend nephrology clinics, the sensitivity was 97% (95% CI, 93.3 to 99.0), and a specificity was 82% (95% CI, 77.4 to 86.1).

Conclusion

A computable phenotype using the ICD-9/10 codes can correctly identify most patients with ADPKD, and can be utilized by researchers to screen health care records for cohorts of patients with ADPKD with acceptable accuracy.

Regional variations in prevalence and severity of autosomal dominant polycystic kidney disease in the United States

OBJECTIVES

To evaluate geographic variation in the prevalence of autosomal dominant polycystic kidney disease (ADPKD) in the US, including ADPKD at risk of rapid progression.

METHODS

Claims data from the IBM MarketScan Commercial and Medicare Supplemental databases (01/16/2016-12/31/2017) were used to estimate the 2017 annual and 2016-2017 two-year prevalence of diagnosed ADPKD and ADPKD at risk of rapid progression in the US overall, and stratified by census regions and states. Risk of rapid progression was identified based on either: hypertension <35 years, hematuria <30 years, albuminuria, stage 2 chronic kidney disease (CKD) <30 years, stage 3 CKD <50 years, and stage 4/5 CKD or kidney transplant <55 years.

RESULTS

Annual prevalence was estimated at 2.34 and two-year prevalence at 3.61 per 10,000 in the US. Across census regions, two-year prevalence per 10,000 was highest in the Northeast (4.14) and lowest in the West (3.35). Prevalence was significantly correlated with the proportion of individuals in urban areas (r = .34, one-sided p = .026). In 2017, 37.5% of patients were identified as being at risk for rapid progression, and this proportion was larger among patients in the South (42.1%, p < .001).

CONCLUSION

This estimate for ADPKD prevalence is consistent with previously reported national estimates, with regional variation suggesting that ADPKD might be under-diagnosed in rural areas with more limited access to care. More than one-third of ADPKD patients presented risk factors associated with rapid progression, highlighting the need for timely identification, as disease-modifying therapy may delay progression to end-stage renal disease.

Excess healthcare costs in patients with autosomal dominant polycystic kidney disease by renal dysfunction stage

AIM

To build upon previous outdated studies by comprehensively assessing the direct healthcare burden of autosomal dominant polycystic kidney disease (ADPKD).

MATERIALS AND METHODS

Patients with ≥2 diagnoses for ADPKD (ADPKD cohort) were identified in the US fee-for-use IBM Truven Health Analytics MarketScan Commercial Claims and Encounters and IBM Truven Health Analytics MarketScan Medicare Supplemental databases (01 January 2015-31 December 2017) and matched (1:3) to controls without ADPKD (non-ADPKD cohort). The index date was the last calendar date followed by 12 months continuous enrollment (study period). Patients with ADPKD were stratified into one of seven mutually exclusive groups based on chronic kidney disease (CKD) stages (I-V), end-stage renal disease requiring renal replacement therapy (ESRD-RRT), and unknown stage.

RESULTS

During the 12-month study period, patients with ADPKD incurred significantly higher total healthcare costs than those without ADPKD (mean cost difference = $22,879 per patient per year [PPPY]; p < .001). Besides CKD stages I and II, total healthcare cost differences increased as patients progressed beyond CKD stage III, with the greatest difference observed among patients with ESRD-RRT. Total healthcare cost differences between cohorts were more pronounced in subgroups of patients with hypertension ($29,347) and with high risk of rapid progression ($39,976). Similar results were observed in the Medicare Supplemental population, with a total mean cost difference of $42,694 PPPY (p < .001); cost difference was also higher in the hypertension ($46,461 PPPY) and high risk of rapid progression ($45,708 PPPY) subgroups.

LIMITATIONS

Results may not be representative of the overall ADPKD US population; CKD stage was based on diagnosis and procedure codes; criteria used to identify ADPKD at risk of rapid progression did not rely on laboratory values; there may be billing inaccuracies and omissions in health insurance claims data.

CONCLUSIONS

This study demonstrated the substantial healthcare costs associated with ADPKD, which increased as patients progressed through more severe CKD stages.

Diagnostic accuracy of administrative codes for autosomal dominant polycystic kidney disease in clinic patients with cystic kidney disease

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.

Analysis of Nationwide Data to Determine the Incidence and Diagnosed Prevalence of Autosomal Dominant Polycystic Kidney Disease in the USA: 2013-2015

BACKGROUND

This study addresses an important gap, as it is the first US nationwide, epidemiologic study of ADPKD incidence and prevalence.

SUMMARY

This 3-year, observational study utilized data from Truven Health MarketScan® administrative claims, as well as cross-sectional data from the National Ambulatory Medical Care Survey (NAMCS). We estimated the annual incidence and diagnosed prevalence using population-based data on over 170 million de-identified patients to provide the most current epidemiologic estimates available. The ADPKD-diagnosed prevalence was 4.3 per 10,000 in the NAMCS, which closely corresponded with age-adjusted rates from patients with either commercial insurance or employer-sponsored Medicare supplemental insurance. The annual incidence was 0.62 per 10,000. Both nationwide data sets indicate that approximately 140,000 patients are currently diagnosed in the USA. We also found significant differences by gender and age. Females are nearly twice as likely as males to be diagnosed in early adulthood, while the incidence in males was highest in those aged 65 years or older. ADPKD appears more likely to be diagnosed in men after disease progression or the development of chronic kidney disease.

KEY MESSAGES

Our results revealed striking age and gender differences in the incidence of ADPKD. Young women are diagnosed with ADPKD at nearly twice the rate of young men, perhaps due to the use of ultrasound in women during child-bearing years. This points to a need for increased recognition of ADPKD, with an emphasis on younger men in particular. ADPKD has been inaccurately perceived as a common condition based on misinterpretation of early epidemiologic data (1957) confirmed by our data and recent European data. ADPKD affects approximately 140,000 patients in the USA and meets the criterion for a rare disease. Our results indicate a need for further study of gender and ADPKD diagnosis, progression, management, and outcomes.

The effect of model selection on cost-effectiveness research: a comparison of kidney function-based microsimulation and disease grade-based microsimulation in chronic kidney disease modeling

BACKGROUND

Cost effectiveness research is emerging in the chronic kidney disease (CKD) research field. Especially, an individual-level state transition model (microsimulation) is widely used for these researches. Some researchers set CKD grades as discrete health states, and the transition probabilities between these states were dependent on the CKD grades (disease grade-based microsimulation, MSM-dg), while others set estimated glomerular filtration rate value which determines the severity of CKD as a main variable describing patients' continuous status (kidney function-based microsimulation, MSM-kf). MSM-kf seems to reflect the real world more precisely but is more difficult to implement. We compared the calculation results of these two microsimulation models to evaluate the effect of model selection on CKD cost-effectiveness analysis.

METHODS

We implemented simplified MSM-dg and MSM-kf emulating natural course of CKD in general, and compared models using parameters derived from an IgA nephropathy cohort. After checking these models' overall behavior, life-years, utilities, and thresholds regarding intervention costs below which the intervention is thought as dominant (V0) or cost-effective (V1) were calculated. In addition, one-way and probabilistic sensitivity analyses were performed.

RESULTS

With base-case parameters, the calculated life-years was shorter in MSM-dg (73.89 vs. 75.80 years) while the thresholds were almost equal (86.87 vs. 90.43 (V0), 132.29 vs. 146.25 [V1 in 1000 USD]) compared to MSM-kf. Sensitivity analyses showed a tendency of the MSM-dg to show shorter results in life-years. V0 and V1 were distributed by approximately ±100,000 USD (V0) and ± 150,000 USD (V1) between models.

CONCLUSIONS

Estimated cost-effectiveness thresholds by both models were not the same and its difference distributed too wide to be ignored. This result indicated that model selection in CKD cost-effectiveness research has large effect on their conclusions.

New and incremental FDA black box warnings from 2008 to 2015

BACKGROUND

The boxed warning (also known as 'black box warning [BBW]') is one of the strongest drug safety actions that the U.S. Food & Drug Administration (FDA) can implement, and often warns of serious risks. The objective of this study was to comprehensively characterize BBWs issued for drugs after FDA approval.

METHODS

We identified all post-marketing BBWs from January 2008 through June 2015 listed on FDA's MedWatch and Drug Safety Communications websites. We used each drug's prescribing information to classify its BBW as new, major update to a preexisting BBW, or minor update. We then characterized these BBWs with respect to pre-specified BBW-specific and drug-specific features.

RESULTS

There were 111 BBWs issued to drugs on the US market, of which 29% (n = 32) were new BBWs, 32% (n = 35) were major updates, and 40% (n = 44) were minor updates. New BBWs and major updates were most commonly issued for death (51%) and cardiovascular risk (27%). The new BBWs and major updates impacted 200 drug formulations over the study period, of which 64% were expected to be used chronically and 58% had available alternatives without a BBW.

CONCLUSIONS

New BBWs and incremental updates to existing BBWs are frequently added to drug labels after regulatory approval.

Cost-effectiveness of angiotensin-converting enzyme inhibitors versus angiotensin II receptor blockers as first-line treatment in autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a rare kidney disorder impacting ∼1:2,500 individuals among the general US population. Hypertension is a significant predictor of ADPKD progression, and a risk factor for development of cardiovascular disease (CVD), the most common cause for mortality among ADPKD patients. Angiotensin-converting enzymes inhibitors (ACE-I) are widely used as first-line treatment in ADPKD for the management of hypertension. However, their cost-effectiveness relative to other hypertensive medications, such as angiotensin II receptor blockers (ARB), has never been assessed.

OBJECTIVE

To determine if ARB are more cost-effective than ACE-Is as first-line treatment in ADPKD.

METHODS

A Markov-state decision model was constructed for estimation of cost and outcome benefits in hypertensive ADPKD patients. Transition probabilities were extrapolated from a retrospective cohort study comparing chronic kidney disease (CKD) stage transitions in ADPKD patients. Annual pharmaceutical costs per average daily dose per CKD stage were extracted from a US healthcare claims database. Median total healthcare costs per CKD stage or transplant were extracted from the published literature. The time horizon was set to 30 years, with 1-year duration to cycle shift. A cost-effectiveness analysis was conducted to estimate the incremental cost-effectiveness ratio (ICER) of ACE-I vs ARB per additional year of prevented transplant and/or death. A one-way probabilistic sensitivity analysis was conducted, with 10% variation in probabilities and cost.

RESULTS

Total annual healthcare costs accrued after 30 years among ADPKD patients taking ACE-Is was estimated to be $3,505,028.41, compared to ARB at $3,644,327.65. Life expectancy was increased by 1.39 years among patients taking ACE-I. Approximate 10-year survival in patients taking ACE-Is was 47% compared to ARB at 34%.

CONCLUSIONS

ACE-I dominated ARB and displayed greater cost-effectiveness due to lower cost and increased capacity to prolong years of life without transplant or death among hypertensive ADPKD patients. This model strengthens the value of ACE-I over ARB as first-line treatment for hypertension management in ADPKD patients.

Incidence and survival of end-stage kidney disease due to polycystic kidney disease in Australia and New Zealand (1963-2014)

BACKGROUND

The aim of this study was to determine whether the incidence and survival of patients with end-stage kidney disease (ESKD) due to polycystic kidney disease (PKD) has changed in Australia and New Zealand.

METHODS

Data for all PKD patients who developed ESKD and commenced renal replacement therapy (RRT) was assessed using the Australia and New Zealand Dialysis and Transplant Registry from 1963 to 2014.

RESULTS

A total 4678 patients with ESKD due to PKD received RRT during the study period. The incidence rate of ESKD (per million population per year) due to PKD rose by 3.2-fold (1970-2010), but the percentage increase between each decade decreased (54.4, 43.8, 25.6 and 6.57%). The median age of onset of new patients developing ESKD has been stable since 1990. Haemodialysis was the most common initial mode of RRT (between 62 and 76% of patients) whereas 24-29% received peritoneal dialysis. The 5-year survival rate of PKD patients on RRT (censored for transplantation and adjusted for age) improved from 26 to 84%, with the percentage increase between each successive time period being 123, 7, 21, 19 and 7.4%. The percentage of deaths on RRT due to cerebrovascular disease declined from 15 to 6%.

CONCLUSIONS

The incidence and age of onset of ESKD due to PKD has remained unchanged in the modern era though patient survival on RRT has continued to improve. These data suggest that the development and implementation of disease-specific treatments prior to RRT is needed to effectively diminish the incidence of ESKD due to PKD.

Positive Predictive Values of International Classification of Diseases, 10th Revision Coding Algorithms to Identify Patients With Autosomal Dominant Polycystic Kidney Disease

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.