Page 135 - Exploring the Potential of Self-Monitoring Kidney Function After Transplantation - Céline van Lint

Self-monitoring: the reliability of patient-reported data 133
was analysed with patients that were hospitalized during the study both in- and excluded. The second sensitivity analysis concerned the test measurements patients were requested to perform when opening a new bottle of strips. Many patients either did not perform test measurements or did not indicate them as such. To prevent test values to be mistakenly considered creatinine measurements, all values that were stored in the device memory were checked. Potential test values were discussed and decided upon by the two main authors. The following criteria were used: 1. the value was not registered in the SMSS, 2. the value differed from the previous and following value, 3. the value fell within the test value range that was set by the manufacturer (133-239 μmol/l) and 4. the value followed or was followed by at least one SMSS-registered value measured on that same day (measured shortly after one another according to device logged data). After having thoroughly checked and discussed all potential test values, for 24 values it remained unclear whether they were test values or not. We therefore performed all analyses concerning the representativeness of registered creatinine data with these 24 values both in- and excluded.
Further, we compared our findings concerning patient self-monitoring creatinine to a more broadly used and well-accepted form of patient-monitoring, being self-monitoring of blood pressure. For this purpose we performed two analyses with the self-monitored and self–reported blood pressure measurements in our study population. First, we looked at adherence to the blood pressure measurement protocol using the same procedure as for creatinine: number of days with measurements versus number of requested measurement days per patient per phase. The requested frequency of blood pressure measurements was equal to the measurement frequency of creatinine. As many patients used other blood pressure devices than the device we supplied for the study, we could not determine adherence to the measurement protocol in a reliable way. We therefore only could assess adherence to the registration protocol by comparing number of registered blood pressure measurements (SMSS logged data) to requested measurement frequency.
Second, we looked at correspondence between measured and registered blood pressures. To prevent potential bias and misinterpretation, we 1. only used measurements from days with an equal number of measurements and registrations and 2. calculated a Mean Arterial Pressure (MAP, [(2 x diastolic)+systolic]/3)) for both measured and registered blood pressures per day. Using all cases of non-correspondence between measured and registered MAP, an overall mean arterial pressure was calculated per patient for both blood pressures that were actually measured and for blood pressures that were registered in the SMSS. A paired t-test was performed comparing these means.
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