Print version ISSN 0211-6995
IBORRA-MOLTO, Carmelo; LOPEZ-ROIG, Sofía and PASTOR-MIRA, M. de los Ángeles. Prevalence of adherence to fluid restriction in kidney patients in haemodialysis: objective indicator and perceived compliance. Nefrología (Madr.) [online]. 2012, vol.32, n.4, pp.477-485. ISSN 0211-6995. http://dx.doi.org/10.3265/Nefrologia.pre2012.Feb.11236.
Introduction: Studies of adherence to fluid restriction show high variability in prevalence data, as different methods of measuring IWG (interdialysis weight gain) and cut-off criteria are used. Objectives: To describe the prevalence of adherence to fluid restriction using daily IWG (criterion: ≤1Kg) and daily IWG adjusted for dry weight (DW) (cut-off point adjusted criterion: DW<70kg, IWG=1kg/day; DW>70kg and ≤80kg, IWG=1.1kg/day; DW>80kg and ≤90kg, IWG=1.2kg/day; DW>90kg, IWG=1.3kg/day) and to study the association between this objective indicator and adherence behaviour as reported by patient. Patients and method: Our study included a total of 146 patients with a mean age of 66 years (SD: 13.6 years; range: 25-88 years), 66% of which were male. Ours was a longitudinal study with one month of follow-up. We collected both sociodemographic and clinical variables and mean daily IWG. Patient-reported adherence behaviour was assessed through an interview by a trained staff member from outside the department who asked the following question: "In order to avoid complications between haemodialysis sessions: during the last month, how many days did you ingest less than 1 litre of fluid per day?" (0= no days; 10= every day). A score ≤5 led to categorisation of patients as compliant with treatment. Statistical analysis included descriptive analysis, correlation test, chi-square and Crosstabs, ROC curve and logistic regression procedures. Results: Prevalence of "objective" adherence to fluid restriction was 61% (mean daily IWG≤1kg) and 73% (mean daily IWG adjusted for dry weight). Reported adherence (prevalence: 56.2%) was associated with IWG adjusted for weight (chi-square =31.34; P=.000). In patients with objective adherence adjusted for weight, the prevalence of reported adherence was 1.65 times that of non-adherence (PR=1.65; 95% CI: 1.29-2.11). The final model for estimating the association between reported adherence behaviour and daily adjusted IWG included: age (higher), dry weight (lower), potassium (lower), time on haemodialysis treatment (less) and its interaction with reported behaviour (F=50.70; P=.000; R2=44%). The sensitivity of reported adherence behaviour for detecting objective adherence adjusted for dry weight was 89%; specificity was 58%, and the overall classification power was 85% (AUC=.85; 95% CI: 0.78-0.92). The probability of objective adherence adjusted for weight in patients who claimed proper adherence was 9 times higher than in non-compliant patients in patients who had been on HD for 2.3 years (PORp25=9.16; 95% CI: 2.58-32.51); 6 times higher in patients on HD for 4.7 years (PORP50=6.16; 95% CI: 2.1217.92); and 3 times higher in those on HD for 8.2 years (PORp75=3.44; 95% CI: 1.32-8.96). Conclusions: Prevalence of adherence to fluid restriction was 73% and 16% depending on daily IWG adjusted/not adjusted for dry weight, respectively. Absolute daily IWG adjusted for weight seems a good indicator of adherence, as it allows for a personalised fluid restriction regimen. Significant association between this objective indicator and reported adherence behaviour supports a combination of patient approach and objective data, which can help with the adjustment of the individual cut-off for daily IWG. This also provides useful information for designing intervention strategies to maintain and increase adherence.
Keywords : Adherence; Perceived compliance; Chronic kidney disease; Interdialytic weight gain; Haemodialysis; Fluid status; Dry weight.