Study protocol
The study subjects were assessed according to the developed protocol, which included the following procedures:
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1. Geriatric interview including, inter alia, age, comorbidity (number of diseases), the recorded history of medications taken.
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2. Geriatric physical examination, including:
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3. Additional blood tests for creatinine, urea and GFR assessment (short version of Modification of Diet in Renal Disease; MDRD).
Study protocol description
Co-morbidity was evaluated by a questionnaire completed by patients during geriatric interview coupled with studying their available medical history. Questions were asked whether subjects were/had been suffering from the following medical conditions: 1) Heart attack, 2) Heart failure, 3) Hypertension, 4) Atherosclerosis, 5) CNS diseases such as stroke, TIA, 6) Hemiparesis, 7) Dementia, 8) Chronic lung disease, 9) Chronic connective tissue disease, 10) Chronic peptic ulcer disease, 11) Chronic liver disease, 12) PCHN, 13) Malignant neoplasm, 14) Chronic hematological diseases, eg. leukemia and 15) Others. One point per condition was awarded whenever confirmed by the subject.
The geriatric interview established what and how many medications were taken daily by the subjects backed up by checking the patient’s medical history notes. Only prescription medication was considered; dietary supplements were excluded. One point was awarded per medication.
The I-ADL scale was used instead of the ADL scale because this evaluates not only basic life functions, but also other complex functions as well as being more effective in those elderly patients without comorbidities. This I-ADL scale assesses eight daily activities: 1) Using the telephone, 2) Doing everyday shopping, 3) Preparing meals, 4) Daily house cleaning, 5) Loading laundry, 6) Using transport, 7) Taking one’s medication and 8) Managing one’s finances. One point was awarded per independently performed activity, with therefore a maximum score of 8 points possible. Zero points were given whenever subjects received help with these activities or whenever they hadn’t actually been engaged in. Thereby, the fewer the points, the less effectively a subject performs such everyday activities. A decrease in I-ADL scores over time indicates that a patient’s general condition is deteriorating.
The second scale used was the Barthel scale because this contains extra and important questions which are absent in the I-ADL scale concerning personal hygiene as well as ones on crucial geriatric issues such as urinary and faecal incontinence. The Barthel scale is also more suited to disabled patients. The scale evaluates ten everyday life activities as follows: 1) Eating meals, 2) Moving (from a bed to chair and back), 3) Maintaining personal hygiene (washing the face, brushing teeth, shaving), 4) Using the toilet, 5) Washing and bathing the whole thing body, 6) Walking on flat ground, 7) Walking upstairs, 8) Getting dressed and undressed, 9) Controlling urination and 10) Controlling defecation.
The following point ranges were adopted according to the scale of difficulty encountered by subjects: 5–15 points for performing activities independently, 5–10 points when assistance is given and zero points for not engaging in any given activity. The maximum possible Barthel score is thus 100 points, with 86–100 being regarded as minor, 21–85 as medium-severe and 0–20 points as a very severe patient’s condition.
The Tinetti test was used to evaluate gait and balance, as this test is regarded as being the gold standard for diagnosing disorders in such areas. A subject fully passing a balance test receives a 16 point maximum while a maximum score of 12 is awarded for the gait test; giving a total maximum score of 28 points. A score of ≤ 25 indicates that there is a risk of falls, and a score of < 19 indicates that a subject's risk of falls increases five times.
The scoring scales assessing functional status by the IADL, Barthel, Tinetti methods can be found in the footnotes at the end of this paper.
Characteristics of the study subjects
The study group were patients aged over 65 years of age, hospitalised at the Nephrology Clinic of the Military Institute of Medicine and those patients under long-term care at the Dialysis Center, also from the Military Institute of Medicine.
According to the guidelines of KDIGO of 2012, CKD is divided according to following GFR classification:
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G1: ≥ 90 ml/min/1,73m2 -normal or increased GFR.
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G2: 60–89 ml/min/1,73m2 -slight reduction in GFR.
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G3a: 45–59 ml/min/1,73m2 -decrease in GFR between slight and moderate.
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G3b: 30–44 ml/min/1,73m2 -reduction in GFR between moderate and severe.
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G4: 15–29 ml/min/1,73m2 -severe decrease in GFR.
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G5: < 15 ml/min/1,73m2 -end-stage renal disease.
This study did not adopt this division into 5 groups (according to the KDIGO guidelines) because after initial analysis of results, it turned out that patients G1 and G2 (GFR > 60 ml/min/1,73m2) had similar results to patients from the control group. For the purposes of this study, the division into 3 groups were thus used.
The participants were divided into groups by using two methods: 1) according to GFR division and, 2) according to division by GFR and functional test results.
The following groups were obtained when the GFR criterion was used:
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- Group-1, the haemodialysis, with CKD stage V (GFR of <15 ml/min/1.73m2); n=28 (where n is number of participants of the group).
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- Group-2, with CKD stage III-IV (GFR of 15-59 ml/min/1.73m2); n=62.
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- Group-3, controls, subjects without CKD, n=23, patients with a GFR of ≥60ml /min/1.73m2 were qualified for this study, without any past history of CKD nor with any additional tests suggesting a past CKD diagnosis).
The following groups were obtained when the GFR criterion was used together with functional test outcomes:
- Group i.1 with CKD stage IV-V (GFR of 0-29 ml/min/1,73m2), n=28, who were on haemodialysis together with n=16 subjects with CKD stage IV that had similar functional test results; giving a total of n=44.
- Group i.2 with CKD stage II-III (GFR of 30-49 ml/min/1,73m2 ) and similar functional test results; n= 34.
- Group i.3, the controls, n=23, CKD-absent and n=12 subjects with a GFR of 50-59 ml/min/1,73m2 that had similar functional test outcomes to those with CKD absent; giving a total of n=35.
The group breakdowns distinguished 3 clusters of patients, corresponding to the 3 patient groups so formed by the primary division according to the GFR described earlier: the CKD group, the hemodialysis group and the control group. Similar results were observed for each group in terms of both renal function markers and the geriatric evaluation tests.
Please note that the MDRD formula was used to calculate the GFR because it is the most common and used one every day in our center. Of course, formulas using Cystatin C are recommended for calculating GFR in the elderly, but their use is not as accessible as MDRD.
Statistics methods
Structural equation modeling was used to statistically measure and analyze the theoretical model adopted, which allows the causal relationships of observed and the underlying latent variables to be flexibly and conveniently mapped according to theoretical reasoning behind such relationships. This method is based on assessing the fit of the empirical variance–covariance matrix, (from the observed data) to the theoretical matrix (designed by the researcher). The stronger the fit, the more closely the data matches the researcher's reasoning as expressed in the structure of the theoretical model. The structural model itself was estimated by the IBM AMOS v.13 using the asymptotically distribution free (ADF) method [9]. The k-means grouping method was used to group patients according to the variables used for building the structural model. This grouping method is based on analyzing how close the Euclid distances are of given observations to the calculated cluster centers; the smaller such distances the more strongly are observations classified to the cluster [10]. The algorithm used aims to minimize the variance within clusters and to maximize the variance between clusters. From the medical point of view, 3 groups of patients were envisaged, therefore, in the k-means analysis, a 3-cluster analysis was forced through. Statistica v.13 software was used for this analysis.
Selected multi-group comparisons of significance were performed by ANOVA (analysis of variance) which determines whether there are any statistically significant differences between independent groups of quantitative variables. It compares intra-group variation with inter-group variation [11]. It found significant, post-hoc testing is used to locate which differences are then significant. This study used the LSD (least significant difference) test for this purpose, to verify the significance of differences between groups per analysed variable.