Participant Perceptions in a Long-term Clinical Trial of Autosomal Dominant Polycystic Kidney Disease.

Rationale & Objective: The development of new therapies for autosomal dominant polycystic kidney disease requires clinical trials to be conducted efficiently. In this study, the factors affecting the recruitment and retention of participants enrolled in a 3-year randomized controlled trial in autosomal dominant polycystic kidney disease were investigated. Study Design: Qualitative study. Setting & Participants: All participants (N=187) were invited to complete a 16-item questionnaire at the final study visit of the primary trial. Participants were recruited to complete a semistructured interview using purposeful sampling according to age, self-reported gender, and randomization group. Analytical Approach: Descriptive statistics were used for demographic data and questionnaires. The interview transcripts underwent inductive thematic coding. Results: One hundred and forty-six of the 187 randomized participants (79%) completed the post-trial questionnaire, and 31 of the 187 participants (21%) completed the interview. Most participants (94%) rated their global satisfaction with the trial as high (a score of 8 or more out of 10). Altruism, knowledge gain, and access to new treatments were the main motivators for recruitment. The main reasons for considering leaving the study were concerns about the risk of intervention and family or work issues. Strategies that favored retention included flexibility in attending different study sites, schedule flexibility, staff interactions, and practical support with parking and reminders. The main burden was time away from work with lost wages, and burden associated with magnetic resonance imaging scans and 24-hour urine output collections. Limitations: The study population was restricted to participants in a single nondrug clinical trial, and the results could be influenced by selection and possible social desirability bias. Conclusions: Participants reported high levels of satisfaction that occurred as a function of the trial meeting participants' expectations. Furthermore, retention was a balance between the perceived benefits and burden of participation. Consideration of these perspectives in the design of future clinical trials will improve their efficiency and conduct. Plain-Language Summary: Advances in the clinical practice of autosomal dominant polycystic kidney disease (ADPKD) require affected individuals to voluntarily participate in long-term multicenter randomized controlled trials (RCTs). In this qualitative post hoc study of a 3-year RCT of increased water intake in ADPKD, altruism, knowledge gain, and access to a nondrug treatment positively influenced the decision to volunteer. Ongoing participation was enabled by building flexibility into the study protocol and staff prioritizing a participant's needs during study visits. Although participants completed the required tests, most were considered burdensome. This study highlights the importance of incorporating protocol flexibility into trial design; the preference for interventions with a low risk of adverse effects; and the urgent requirement for robust surrogate noninvasive biomarkers to enable shorter RCTs in ADPKD.

Prescribed Water Intake in Autosomal Dominant Polycystic Kidney Disease.

BACKGROUND: Arginine vasopressin promotes kidney cyst growth in autosomal dominant polycystic kidney disease (ADPKD). Increased water intake reduces arginine vasopressin and urine osmolality and may slow kidney cyst growth. METHODS: In this randomized controlled 3-year clinical trial, we randomly assigned adults with ADPKD who had a height-corrected total kidney volume in Mayo imaging subclass categories 1B to 1E and an estimated glomerular filtration rate of 30 ml/min/1.73 m2 or greater to (1) water intake prescribed to reduce 24-hour urine osmolality to 270 mOsmol/kg or less or (2) ad libitum water intake irrespective of 24-hour urine osmolality. The primary end point was the percentage annualized rate of change in height-corrected total kidney volume. RESULTS: A total of 184 patients participated in either the ad libitum water intake group (n=92) or the prescribed water intake group (n=92). Over 3 years, there was no difference in the annualized rate of change in height-corrected total kidney volume between the ad libitum (7.8% per year; 95% confidence interval [CI], 6.6 to 9.0) and prescribed (6.8% per year; 95% CI, 5.8 to 7.7) water intake groups (mean difference, −0.97% per year; 95% CI, −2.37 to 0.44; P=0.18). The difference in mean 24-hour urine osmolality between the ad libitum and prescribed water intake groups was −91 mOsmol/kg (95% CI, −127 to −54 mOsmol/kg), with 52.3% of patients achieving adherence to the target 24-hour urine osmolality and no reduction in serum copeptin over 3 years. The frequency of adverse events was similar between groups. CONCLUSIONS: For patients with ADPKD, prescribed water intake was not associated with excess adverse events and achieved the target 24-hour urine osmolality for half of the patients but did not reduce copeptin or slow the growth of total kidney volume over 3 years compared with ad libitum water intake. (Funded by the National Health and Medical Research Council of Australia [grant GNT1138533], Danone Research, PKD Australia, the University of Sydney, and the Westmead Medical Research Foundation; Australian New Zealand Clinical Trials Registry number, ACTRN12614001216606).

Assessment of Dietary Sodium Intake Using the Scored Salt Questionnaire in Autosomal Dominant Polycystic Kidney Disease.

The excess intake of dietary sodium is a key modifiable factor for reducing disease progression in autosomal dominant polycystic kidney disease (ADPKD). The aim of this study was to test the hypothesis that the scored salt questionnaire (SSQ; a frequency questionnaire of nine sodium-rich food types) is a valid instrument to identify high dietary salt intake in ADPKD. The performance of the SSQ was evaluated in adults with ADPKD with an estimated glomerular filtration rate (eGFR) ≥ 30 mL/min/1.73 m2 during the screening visit of the PREVENT-ADPKD trial. High dietary sodium intake (HSI) was defined by a mean 24-h urinary sodium excretion ≥ 100 mmol/day from two collections. The median 24-h urine sodium excretion was 132 mmol/day (IQR: 112-172 mmol/d) (n = 75; mean age: 44.6 ± 11.5 years old; 53% female), and HSI (86.7% of total) was associated with male gender and higher BMI and systolic blood pressure (p < 0.05). The SSQ score (73 ± 23; mean ± SD) was weakly correlated with log10 24-h urine sodium excretion (r = 0.29, p = 0.01). Receiving operating characteristic analysis showed that the optimal cut-off point in predicting HSI was an SSQ score of 74 (area under the curve 0.79; sensitivity 61.5%; specificity 90.0%; p < 0.01). The evaluation of the SSQ in participants with a BMI ≥ 25 (n = 46) improved the sensitivity (100%) and the specificity (100%). Consumers with an SSQ score ≥ 74 (n = 41) had higher relative percentage intake of processed meats/seafood and flavourings added to cooking (p < 0.05). In conclusion, the SSQ is a valid tool for identifying high dietary salt intake in ADPKD but its value proposition (over 24-h urinary sodium measurement) is that it may provide consumers and their healthcare providers with insight into the potential origin of sodium-rich food sources.

Randomised controlled trial to determine the efficacy and safety of prescribed water intake to prevent kidney failure due to autosomal dominant polycystic kidney disease (PREVENT-ADPKD).

INTRODUCTION: Maintaining fluid intake sufficient to reduce arginine vasopressin (AVP) secretion has been hypothesised to slow kidney cyst growth in autosomal dominant polycystic kidney disease (ADPKD). However, evidence to support this as a clinical practice recommendation is of poor quality. The aim of the present study is to determine the long-term efficacy and safety of prescribed water intake to prevent the progression of height-adjusted total kidney volume (ht-TKV) in patients with chronic kidney disease (stages 1-3) due to ADPKD. METHODS AND ANALYSIS: A multicentre, prospective, parallel-group, open-label, randomised controlled trial will be conducted. Patients with ADPKD (n=180; age ≤65 years, estimated glomerular filtration rate (eGFR) ≥30 mL/min/1.73 m2) will be randomised (1:1) to either the control (standard treatment+usual fluid intake) or intervention (standard treatment+prescribed fluid intake) group. Participants in the intervention arm will be prescribed an individualised daily fluid intake to reduce urine osmolality to ≤270 mOsmol/kg, and supported with structured clinic and telephonic dietetic review, self-monitoring of urine-specific gravity, short message service text reminders and internet-based tools. All participants will have 6-monthly follow-up visits, and ht-TKV will be measured by MRI at 0, 18 and 36 months. The primary end point is the annual rate of change in ht-TKV as determined by serial renal MRI in control vs intervention groups, from baseline to 3 years. The secondary end points are differences between the two groups in systemic AVP activity, renal disease (eGFR, blood pressure, renal pain), patient adherence, acceptability and safety. ETHICS AND DISSEMINATION: The trial was approved by the Human Research Ethics Committee, Western Sydney Local Health District. The results will inform clinicians, patients and policy-makers regarding the long-term safety, efficacy and feasibility of prescribed fluid intake as an approach to reduce kidney cyst growth in patients with ADPKD. TRIAL REGISTRATION NUMBER: ANZCTR12614001216606.