Patient-Reported Factors Associated With Poor Phosphorus Control in a Maintenance Hemodialysis Population

Establishing the criterion validity of self-report measures of adherence in hemodialysis through associations with clinical biomarkers: A systematic review and meta-analysis

Accurate measurement of adherence is crucial to rigorously evaluate interventions aimed at improving this outcome in patients undergoing in-center hemodialysis. Previous research has shown great variability in non-adherence rates between studies, mainly due to the use of different direct (e.g., clinical biomarkers) and indirect (e.g., questionnaires) measures. Although self-reported adherence in hemodialysis has been widely explored, it is still unclear which is the most accurate questionnaire to assess this outcome; therefore, the question of how to optimize adherence measurement in research and clinical practice has emerged as a key issue that needs to be addressed. This systematic review and meta-analysis aimed to explore the criterion validity of self-report measures of adherence in hemodialysis established through the association between test scores and clinical biomarkers (the criterion measure). The protocol was registered in PROSPERO (2021 CRD42021267550). The last search was performed on March 29th, 2022, on Web of Science (all databases included), Scopus, CINHAL, APA PsycInfo, and MEDLINE/PubMed. Twenty-nine primary studies were included, and thirty-eight associations were analyzed. The Hunter-Schmidt's meta-analysis was computed for the associations with more than two studies (n = 20). The results showed that six associations were large (16%), 11 were medium (29%) and the remaining were of small strength. The test scores from the End-Stage Renal Disease Adherence Questionnaire (range: 0.212<rc <0.319) and the Dialysis Diet and Fluid Non-Adherence Questionnaire (range: 0.206<rc <0.359) had medium to large strength associations with interdialytic weight gain, serum phosphorus, and potassium levels, indicating that these questionnaires have reasonable concurrent criterion validity to measure fluid control and adherence to dietary restrictions in patients receiving hemodialysis. The available data did not allow exploring the criterion validity of the test scores in relation to hemodialysis attendance (skipping and/or shortening sessions). These results suggest that the decision to use one questionnaire over another must be made with caution, as researchers need to consider the characteristics of the sample and the objectives of the study. Given that direct and indirect methods have their advantages and disadvantages, the combination of adherence measures in hemodialysis is recommended to accurately assess this complex and multidimensional outcome.

Effectiveness of a Nutritional Mobile Application for Management of Hyperphosphatemia in Patients on Hemodialysis: A Multicenter Open-Label Randomized Clinical Trial

This study aims to determine the effectiveness of a phosphate mobile app (PMA), MyKidneyDiet-Phosphate Tracker ©2019, on hemodialysis (HD) patients with hyperphosphatemia. A multicenter, open-label, randomized controlled trial design allowed randomization of patients with hyperphosphatemia to either the usual care group (UG; receiving a single dietitian-led session with an education booklet) or the PMA group (PG). Thirty-three patients in each intervention group completed the 12-week study. Post-intervention, serum phosphorus levels were reduced in both groups (PG: −0.25 ± 0.42 mmol/L, p = 0.001; UG: −0.23 ± 0.33 mmol/L, p < 0.001) without any treatment difference (p > 0.05). Patients in both groups increased their phosphate knowledge (PG: 2.18 ± 3.40, p = 0.001; UG: 2.50 ± 4.50, p = 0.003), without any treatment difference (p > 0.05). Dietary phosphorus intake of both groups was reduced (PG: −188.1 ± 161.3 mg/d, p < 0.001; UG: −266.0 ± 193.3 mg/d, p < 0.001), without any treatment difference (p > 0.05). The serum calcium levels of patients in the UG group increased significantly (0.09 ± 0.20 mmol/L, p = 0.013) but not for the PG group (−0.03 ± 0.13 mmol/L, p = 0.386), and the treatment difference was significant (p = 0.007). As per phosphate binder adherence, both groups reported a significant increase in Morisky Medication Adherence Scale scores (PG: 1.1 ± 1.2, p < 0.001; UGa: 0.8 ± 1.5, p = 0.007), without any treatment difference (p > 0.05). HD patients with hyperphosphatemia using the PMA achieved reductions in serum phosphorus levels and dietary phosphorus intakes along with improved phosphate knowledge and phosphate binder adherence that were not significantly different from a one-off dietitian intervention. However, binder dose adjustment with meal phosphate content facilitated by the PMA allowed stability of corrected calcium levels, which was not attained by UC patients whose binder dose was fixed.

Inhibition of sodium/hydrogen exchanger 3 in the gastrointestinal tract by tenapanor reduces paracellular phosphate permeability

Hyperphosphatemia is common in patients with chronic kidney disease and is increasingly associated with poor clinical outcomes. Current management of hyperphosphatemia with dietary restriction and oral phosphate binders often proves inadequate. Tenapanor, a minimally absorbed, small-molecule inhibitor of the sodium/hydrogen exchanger isoform 3 (NHE3), acts locally in the gastrointestinal tract to inhibit sodium absorption. Because tenapanor also reduces intestinal phosphate absorption, it may have potential as a therapy for hyperphosphatemia. We investigated the mechanism by which tenapanor reduces gastrointestinal phosphate uptake, using in vivo studies in rodents and translational experiments on human small intestinal stem cell-derived enteroid monolayers to model ion transport physiology. We found that tenapanor produces its effect by modulating tight junctions, which increases transepithelial electrical resistance (TEER) and reduces permeability to phosphate, reducing paracellular phosphate absorption. NHE3-deficient monolayers mimicked the phosphate phenotype of tenapanor treatment, and tenapanor did not affect TEER or phosphate flux in the absence of NHE3. Tenapanor also prevents active transcellular phosphate absorption compensation by decreasing the expression of NaPi2b, the major active intestinal phosphate transporter. In healthy human volunteers, tenapanor (15 mg, given twice daily for 4 days) increased stool phosphorus and decreased urinary phosphorus excretion. We determined that tenapanor reduces intestinal phosphate absorption predominantly through reduction of passive paracellular phosphate flux, an effect mediated exclusively via on-target NHE3 inhibition.

An Analysis of Medication Adherence and Patient Preference in Long-term Stable Maintenance Hemodialysis Patients in Japan

Objective This follow-up survey report describes medication adherence and patient preferences, beliefs, and expectations of maintenance hemodialysis treatment in Japan. Methods This patient-reported questionnaire-based survey was conducted in six regions in Japan from September 2016 to November 2016. Patients The questionnaire was provided to 700 patients (50-79 years old) on maintenance hemodialysis for >3 years who were members of the Japan Association of Kidney Disease Patients. Patients were randomly selected by a stratified sampling method based on patient distribution observed from the Japanese Society for Dialysis Therapy Renal Data Registry. Results A total of 524 (74.9%) complete patient questionnaires were evaluated; the mean (SD) age was 66.6 (7.2) years (men, 63.4%) with a dialysis vintage of 16.9 (9.1) years. Adherence was high for all types of medications: between 76.7% for phosphate binders and 95.7% for antidiabetic medications. The most common reason for a missed dose was forgetting to take medication [52.5% (117/223)]. Patient preference for oral medication was as low as 0.9% (1/110), 9% (31/345), and 2.9% (2/69) for patients who felt mental burden, felt no mental burden, and neither, respectively, with their current treatment regimen. In addition, 37.8% (198/524) of patients responded that the elimination of 1 medication (1 tablet) would reduce their mental burden. Conclusion The results of this survey show that overall medication adherence is high in Japanese patients on maintenance hemodialysis. While many patients perceive an absence of mental burden, they still prefer to avoid oral medication when possible.

One-Year Historical Cohort Study of the Phosphate Binder Sucroferric Oxyhydroxide in Patients on Maintenance Hemodialysis

OBJECTIVE

The high pill burden of many phosphate binders (PBs) may contribute to increased prevalence of hyperphosphatemia and poor nutritional status observed among patients undergoing maintenance hemodialysis therapy. We examined the real-world effectiveness of sucroferric oxyhydroxide (SO), a PB with low pill burden, in managing serum phosphorus in patients with prevalent hemodialysis over a 1-year period.

DESIGN

Historical cohort analyses of de-identified electronic medical records.

SUBJECTS

In-center hemodialysis patients switched from another PB to SO therapy as part of routine care with 12 months of uninterrupted SO prescriptions recorded, and documented serum phosphorus levels were eligible for inclusion. Clinical data were extracted from a pharmacy service, FreseniusRx, database and Fresenius Kidney Care clinical data warehouse.

MAIN OUTCOME MEASURES

Comparisons were made between the 91-day period before SO initiation (i.e., baseline) and the 4 consecutive 91-day intervals of SO treatment (Q1-Q4). Clinical measures included achievement of target phosphorus levels (≤5.5 mg/dL) and mean number of PB pills/day.

RESULTS

Among 530 analyzed patients, the proportion achieving target serum phosphorus levels increased by >100% 1 year after switching to SO therapy, that is, from 17.7% at baseline to 24.5%, 30.5%, 36.4%, and 36.0% at Q1 through Q4, respectively (P < .0001 for all). Reductions in serum phosphorus were observed at all follow-up timepoints (P < .0001), irrespective of baseline PB. From a mean baseline PB pill burden of 8.5 pills/day, patients experienced an average 50% pill burden reduction during SO treatment (P < .0001). Phosphorus-attuned albumin and phosphorus-attuned protein intake (normalized protein catabolic rate) improved significantly after transition to SO (P < .0001). The effectiveness of SO was evident in prespecified subgroups of interest (i.e., black/African-American patients, Hispanic/Latino patients, and women).

CONCLUSION

Among patients on hemodialysis, switching to SO resulted in a 2-fold greater likelihood of achieving target phosphorus levels while halving daily PB pill burden. Increases in phosphorus-attuned albumin and protein intake suggest improved nutritional status.

Use of Phosphorus Binders among Non-Dialysis Chronic Kidney Disease Patients and Mortality Outcomes

BACKGROUND

Whether the benefits of phosphorus binders extend to those without end stage renal disease is uncertain. Among a large diverse non-dialysis chronic kidney disease (CKD) population with hyperphosphatemia, we sought to evaluate phosphorus binder use and compare mortality risk between patients prescribed and not prescribed binders.

METHODS

A retrospective cohort study within an integrated health system (January 1, 1998 - December 31, 2012) among CKD patients (age ≥18) was performed. Non-dialysis CKD patients with 2 separate estimated glomerular filtrate rate (eGFR) <30 mL/min/1.73 m2 and serum phosphorus ≥5.0 mg/dL within 180 days of eGFR were included. Multivariable cox proportional hazards and inverse probability of treatment-weighted models were used to estimate mortality hazard ratios (HRs) for patients who received phosphorus binders compared to no binders.

RESULTS

Among 10,165 study patients, 2,733 subjects (27%) received phosphorus binders. Compared to the no-phosphorus-binder group, the binder group had mortality HRs (95% CI) of 0.86 (0.79-0.94) and 0.86 (0.80-0.93) using traditional multivariable and inverse probability of treatment-weighted models respectively. Sensitivity analyses removing patients who were prescribed binders >180 days after index date revealed no difference in mortality between those with binders and with no binders.

CONCLUSION

Our findings from a real-world clinical environment revealed that 27% of hyperphosphatemic non-dialysis CKD patients were prescribed binders. They also had lower risk of mortality compared to those not prescribed phosphorus binders. However, the lower mortality risk was not observed when we accounted for immortal time bias. Whether phosphorus binder use in CKD improves survival remains to be determined.

Health care providers' support of patients' autonomy, phosphate medication adherence, race and gender in end stage renal disease

This study was designed to assess dialysis subjects' perceived autonomy support association with phosphate binder medication adherence, race and gender. A multi-site cross-sectional study was conducted among 377 dialysis subjects. The Health Care Climate (HCC) Questionnaire assessed subjects' perception of their providers' autonomy support for phosphate binder use, and adherence was assessed by the self-reported Morisky Medication Adherence Scale. Serum phosphorus was obtained from the medical record. Regression models were used to examine independent factors of medication adherence, serum phosphorus, and differences by race and gender. Non-white HCC scores were consistently lower compared with white subjects' scores. No differences were observed by gender. Reported phosphate binder adherence was associated with HCC score, and also with phosphorus control. No significant association was found between HCC score and serum phosphorus. Autonomy support, especially in non-white end stage renal disease subjects, may be an appropriate target for culturally informed strategies to optimize mineral bone health.