Chronic Kidney Disease and Micronutrients

Citation:
 
Study Design:
Class:
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Quality Rating:
Research Purpose:

To determine whether vitamin D therapy had an additional protective effect against loss of allograft function among renal transplant recipients.

Inclusion Criteria:

Patients who had undergone deceased donor and living-related renal transplantation between 1995 and 2001. The duration of graft functioning was more than 12 months.

Exclusion Criteria:
  • Recurrence of original disease
  • Age less than 18 years
  • Noncompliance with medical therapy.
Description of Study Protocol:

Recruitment

Retrospective data analyses with all patients fulfilled inclusion criteria with a mean post-transplantation follow-up time of 50.7±18.9 months.

Design

Retrospective cohort study.

Intervention

Patients was administered calcitriol because of osteoporosis (Group 1). Osteoporosis was defined by bone mineral density at the beginning of the calcitriol therapy.

Mean time to start calcitriol therapy was 22.4±6.0 months post-transplantation.

Statistical Analysis

 Student T-test or Mann-Whitney U-test.

Data Collection Summary:

Timing of Measurements

  • Biochemical measurements were recorded before and after the initiation of calcitriol therapy at six-month intervals for two successive years in both groups
  • BMI was calculated at six-month intervals during the first year post-transplantation and yearly thereafter.

Dependent Variables

  • Acute rejection episodes suspected on clinical grounds were always confirmed using kidney biopsy
  • Creatinine, Ca, P, PTH and CRP levels
  • BMI.

Independent Variables

Patients was administered calcitriol because of osteoporosis (Group 1) was compared with other patients (Group 2) without osteoporosis who did not receive calcitriol.

Control Variables

Group 1 patients were matched with Group 2 patients for age, gender, donor source, transplantation duration, acute rejection episodes and immunosuppressives received at the first and second years of the post-transplantation period.

Description of Actual Data Sample:
  • Initial N: 110 (78 males, 32 females)
  • Attrition (final N): 110 (78 males, 32 females)
  • Age: 35.2±11.4 years
  • Other relevant demographics: Mean creatinine level before calcitriol therapy, 1.6mg per dL in Group 1; 1.3mg per dL in Group 2 (P=NS)
  • Anthropometrics: Mean pre-transplant BMI, 19.9kg/m2 in Group 1; 21.0kg/m2 in Group 2; P<0.03 between groups
  • Location: Turkey.
Summary of Results:

 

 
Group 1: Vitamin D Treatment (N=57)
Group 2: No Treatment (N=53)
P
Pre-transplant BMI (kg/m2)
19.9±2.6
21.0±2.5
0.03
BMI after the second year of calcitriol Rx
22.0±3.1
23.2±2.1
0.02
Calcium before calcitriol Rx (mg per dL)
9.4±0.6
9.4±0.7
NS
Calcium after the second year of calcitriol Rx (mg per dL)
9.6±0.6
9.3±0.6
0.03
Phosphorus before calcitriol Rx (mg per dL)
3.4±0.8
3.3±0.8
NS
Phosphorus after the second year of calcitriol Rx (mg per dL)
3.3±0.8
3.5±0.8
NS
Creatinine level before calcitriol Rx (mg per dL)
1.6±0.7
1.3±0.3
NS
Creatinine after the first year of calcitriol Rx (mg per dL)
1.6±0.6
2.5±2.2
0.01
Creatinine after the second year of calcitriol Rx (mg per dL)
1.7±1.4
2.7±2.5
0.02
PTH before calcitriol Rx (mg per dL)
96.9±77.1
56.6±27.9
NS
PTH after the second year of calcitriol Rx (mg per dL)
166.4±218.4
517.5±793.3
0.04
Pulse steroid dose after the second year of calcitriol Rx (mg)
3,507±1,997.4
4,553±2,323.6
0.04

Although there was no significant difference in the number of acute rejection episodes between the groups, patients who had been given calcitriol needed fewer pulse steroid doses (P<0.04).

All patients were considered free of chronic allograft nephropathy.

Author Conclusion:

Calcitriol therapy, in addition to its therapeutic and protective effects on post-transplantation osteoporosis, may be used safely, leading to a deceleration in the rate of loss of renal function among renal transplant recipients.

Funding Source:
Other: No data
Reviewer Comments:

Observational study with very selected groups of patients. Non-compliant patients were excluded. The results may not be applicable to all patients.

Comparison group (Group 2) may have had better nutrition status before and after transplantation (significantly higher BMI than Group 1).

Doses of vitamin D treatment were not reported.

Changes in BMD and GFR were not reported, so the authors' conclusions were only based on less valid markers for osteoporosis and kidney function.

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? No
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? No
  2.2. Were criteria applied equally to all study groups? No
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? No
3. Were study groups comparable? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? No
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? No
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? No
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? No
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? No
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? No
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  6.6. Were extra or unplanned treatments described? No
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? ???
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? No
  7.5. Was the measurement of effect at an appropriate level of precision? No
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? N/A
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? No
  8.1. Were statistical analyses adequately described and the results reported appropriately? No
  8.2. Were correct statistical tests used and assumptions of test not violated? No
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? No
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
9. Are conclusions supported by results with biases and limitations taken into consideration? No
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
10. Is bias due to study's funding or sponsorship unlikely? ???
  10.1. Were sources of funding and investigators' affiliations described? ???
  10.2. Was the study free from apparent conflict of interest? ???