Page 106 - Exploring the Potential of Self-Monitoring Kidney Function After Transplantation - Céline van Lint

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Chapter 5
2.1. Participant recruitment and assignment
Power calculation used the within-group standard deviation for differences in renal function of two historic kidney transplant cohorts (3.8 ml/min). The tolerance limit for differences between groups was set to 3.0 ml/min. With a robust beta (power of 95%), an alpha of .05 and 2-tailed testing, a sample size of at least 42 per group was needed.
Patients were eligible for participation if their living donor transplantation was scheduled or if they were still hospitalized after having received a kidney from a deceased donor within period of inclusion (March 2012 - May 2014), were ≥18 years of age, mastered the Dutch language sufficiently, had sufficient computer skills and access to Internet, could perform the required actions independently and had a creatinine level of ≤300 μmol/l within 4 weeks post-transplantation (due to lower reliability of the creatinine device for values >300 μmol/l). Patients were excluded if they had insufficient understanding of the treatment and/or had a history of incompliance.
During a pre-transplant appointment with a nurse-practitioner aimed at informing patients about the transplantation procedure in the LUMC, patients were shortly introduced to the study and received a detailed description of the study design and informed consent form. If a signed informed consent form was not returned within 2 weeks from the appointment, patients were contacted by the primary investigator to inform whether they were (still) interested in participation. Each participant was assigned a study number in consecutive order. Study numbers were allocated to either the intervention or control group according to a pre-set randomization schedule with a 1:1 ratio. The randomization list was produced by means of random permutations of therapies within blocks of length 10 with 5 occurrences of each of the two therapies per block. A Statistical Package for the Social Sciences (SPSS) program (syntax) was written for this purpose by the statistician. For the last 6 months of inclusion, a new randomization list was created by the statistician with a 2:1 ratio as the intervention-control distribution became skewed. The randomization procedure was blinded for the project members directly involved in patient recruitment.
2.2. Materials
Patients received a StatSensor® Xpress-iTM Creatinine Hospital Meter (Nova Biomedical, Waltham, USA) and measurement accessories (i.e. test strips, control solution and safety lancets for capillary blood sampling) to self-monitor creatinine. Further, they received a Microlife WatchBP® Home (Microlife, Heerbrugg, Switzerland), an oscillometric device for blood pressure self-measurement on the upper arm. Both devices had a memory function and the option to download stored values to a computer. Test results were registered in an Internet-based self-management support system (SMSS). For