Structural Equation Modelling to Identify Psychometric Determinants of Medication Adherence in a Survey of Kidney Dialysis Patients.

Purpose: Medication non-adherence in dialysis patients is associated with increased mortality and higher healthcare costs. We assessed whether medication adherence is influenced by specific psychometric constructs measuring beliefs about the necessity for medication and concerns about them. We also tested whether medication knowledge, health literacy, and illness perceptions influenced this relationship. Patients and Methods: This study is based on data from a cross-sectional in-person questionnaire, administered to a random sample of all adult dialysis patients at a teaching hospital. The main outcome was self-assessed medication adherence (8-Item Morisky Medication Adherence Scale). The predictors were: concerns about medications and necessity for medication (Beliefs About Medication Questionnaire); health literacy; medication knowledge (Medication Knowledge Evaluation Tool); cognitive, emotional, and comprehensibility Illness perceptions (Brief Illness Perception Questionnaire). Path analysis was performed using structural equations in both covariance and variance-based models. Results: Necessity for medication increased (standardized path coefficient [ß] 0.30 [95% CI 0.05, 0.54]) and concerns about medication decreased (standardized ß -0.33 [-0.57, -0.09]) medication adherence, explaining most of the variance in outcome (r2=0.95). Medication knowledge and cognitive illness perceptions had no effects on medication adherence, either directly or indirectly. Higher health literacy, greater illness comprehension, and a more positive emotional view of their illness had medium-to-large sized effects in increasing medication adherence. These were indirect rather and direct effects mediated by decreases in concerns about medications (standardized ß respectively -0.40 [-0.63,-0.16], -0.60 [-0.85, -0.34], -0.33 [-0.52, -0.13]). Conclusion: Interventions that reduce patients' concerns about their medications are likely to improve adherence, rather than interventions that increase patients' perceived necessity for medication. Improving patients' general health literacy and facilitating a better understanding and more positive perception of the illness can probably achieve this. Our study is potentially limited by a lack of generalizability outside of the population and setting in which it was conducted.

Understanding barriers to optimal medication management for those requiring long-term dialysis: rationale and design for an observational study, and a quantitative description of study variables and data.

BACKGROUND: Rates of medication non-adherence in dialysis patients are high, and improving adherence is likely to improve outcomes. Few data are available regarding factors associated with medication adherence in dialysis patients, and these data are needed to inform effective intervention strategies. METHODS/DESIGN: This is an observational cross-sectional study of a multi-ethnic dialysis cohort from New Zealand, with the main data collection tool being an interviewer-assisted survey. A total of 100 participants were randomly sampled from a single centre, with selection stratified by ethnicity and dialysis modality (facility versus home). The main outcome measure is self-reported medication adherence using the Morisky 8-Item Medication Adherence Scale (MMAS-8). Study data include demographic, clinical, social and psychometric characteristics, the latter being constructs of health literacy, medication knowledge, beliefs about medications, and illness perceptions. Psychometric constructs were assessed through the following survey instruments; health literacy screening questions, the Medication Knowledge Evaluation Tool (Okuyan et al.), the Beliefs about Medication Questionnaire (Horne et al.), the Brief Illness Perception Questionnaire (Broadbent et al.). Using the study data, reliability analysis for internal consistency is satisfactory for the scales evaluating health literacy, medication knowledge, and beliefs about medications, with Chronbach's α > 0.7 for all. Reliability analysis indicated poor internal consistency for scales relating to illness perceptions. MMAS-8 and all psychometric scores are normally distributed in the study data. DISCUSSION: This study will provide important information on the factors involved in medication non-adherence in New Zealand dialysis patients. The resulting knowledge will inform long-term initiatives to reduce medication non-adherence in dialysis patients, and help ensure that they are addressing appropriate and evidence based targets for intervention.

The estimation of glomerular filtration rate in an Australian and New Zealand cohort.

BACKGROUND: Accurate estimation of glomerular filtration rate (GFR) allows early detection of renal disease and maximizes opportunity for intervention. AIM: To assess the accuracy of estimated GFR (eGFR) in an Australian and New Zealand cohort with chronic kidney disease using the 4-variable Modification of Diet in Renal Disease equation (MDRD(4V)), the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations, and the Cockcroft and Gault equation with actual and ideal body weight. METHODS: Retrospective review of patients who had measured GFR (mGFR) by 51Cr-EDTA clearance and simultaneous measurements of serum biochemistry and anthropometrics. eGFR was compared with mGFR using the concordance correlation coefficient (CCC) and Bland-Altman measures of agreement. RESULTS: 178 patients had 441 radioisotope measurements of GFR. Mean mGFR of was 22.6 mL/min per 1.73 m(2) . The MDRD(4V) equation using the 'black' correction factor was most accurate with a mean eGFR of 19.74 (CCC 0.733, bias -2.86). The CKD-EPI equations also using the 'black' correction factors were almost as good at 19.11 (CCC 0.719, bias -3.49). The Cockcroft-Gault creatinine clearance values had the poorest agreement with mGFR. In the 18 nonwhite non-Asian patients, the MDRD(4V) and CKD-EPI equations were generally less accurate although the use of the 'black' correction factor resulted in greater accuracy for both equations. CONCLUSION: The MDRD(4V) equation was the most accurate. However, its accuracy might be less for nonwhite non-Asian patients if the 'black' correction factor is omitted. Further study of the estimation of GFR in Australian and New Zealand ethnic subgroups would be helpful.

Mortality rate comparison after switching from continuous to prolonged intermittent renal replacement for acute kidney injury in three intensive care units from different countries.

BACKGROUND: Prolonged intermittent renal replacement therapy (PIRRT) is a dialysis modality for critically ill patients that in theory combines the superior detoxification and haemodynamic stability of the continuous renal replacement therapy (CRRT) with the operational convenience, reduced haemorrhagic risk and low cost of conventional intermittent haemodialysis. However, the extent to which PIRRT should replace these other modalities is uncertain because comparative studies of mortality are lacking. We retrospectively examined the mortality data from three general intensive care units (ICUs) in different countries that have switched their predominant therapeutic approach from CRRT to PIRRT. We assessed whether this practice change was associated with a change in mortality rate. METHODS: Data were analysed from ICUs in New Zealand, Australia and Italy. The study population comprised all patients requiring renal replacement therapy from 1 January 1995 to 31 December 2005 (n = 1347), the period of time spanning the change from CRRT to PIRRT in each unit. Poisson regression models were used to estimate the incident rate ratio (IRR) for death, comparing the periods before and after change to PIRRT in each unit. Estimates were adjusted for patient illness severity (APACHE II score) and for the underlying time trend in mortality rate over time. RESULTS: The change from CRRT to PIRRT was not associated with any increase in mortality rate, with an adjusted IRR of 1.02 (0.61-1.71). The IRR was virtually identical in the three ICUs (P-value = 0.63 for the difference in the IRR between ICUs). CONCLUSIONS: Switching from CRRT to PIRRT was not associated with a change in mortality rate. Pending the results of a randomized trial, our study provides evidence that PIRRT might be equivalent to CRRT in the general ICU patient.

Regional citrate anticoagulation during simulated treatments of sustained low efficiency diafiltration.

Renal replacement therapy is frequently required for critically ill patients with a high risk of bleeding. Conventional heparinization strategies to prevent extracorporeal blood circuit clotting can cause significant haemorrhage in such patients because of systemic anticoagulation. Regional citrate anticoagulation (RCA) is a well-established technique that minimizes this complication by the decalcification of blood in the extracorporeal circuit such that it is incapable of clotting. To date, there are no reports on the use of RCA for sustained low-efficiency dialysis/diafiltration (SLED), a hybrid therapy that involves the use of conventional haemodialysis machinery to deliver lower solute clearances over prolonged periods of time. In preparation for clinical study, an in vitro simulation of SLED was devised (blood substitute flow 250 mL/min, dialysate flow 200 mL/min, predilution haemofiltration 100 mL/min). Blood substitute was decalcified by an infusion of 4% trisodium citrate (TSC) proximally into the extracorporeal blood circuit, with partial restoration of calcium homeostasis from dialysate containing ionized [Ca2+] at 0.9 mmol/L. This simulation was used to establish first the 4% TSC requirement for therapeutic decalcification, and second the associated changes in ionized [Ca2+] and [Mg2+] within the blood substitute from chelation with citrate and subsequent removal of the resulting divalent cation-citrate complex. Serial measurements of blood substitute [Ca2+] from strategic points along the extracorporeal circuit showed therapeutic decalcification was not achieved with 4% TSC infusion rates up to 400 mL/h, and extrapolation of experimental results suggests that 450 mL/h will be required. Under these conditions, ionized [Ca2+] and [Mg2+] in the blood substitute venous return and would be 0.42 and 0.2 mmol/L, respectively, with 0.35 mmol of citrate being returned per minute via the blood substitute venous return. These results were modelled for various changes in SLED operating parameters, and discussed in detail. An appropriate regimen for 4% TSC infusion and divalent cation replacement is proposed for clinical study in the future.