CKD: Acid-Base Balance (2018)

Author and Year:
Goraya et al 2014
PubMed ID:
Article Title:
Treatment of metabolic acidosis in patients with stage 3 chronic kidney disease with fruits and vegetables or oral bicarbonate reduces urine angiotensinogen and preserves glomerular filtration rate.
Goraya N, Simoni J, Jo C, Wesson D
Kidney International
Year of publication:
Page numbers:
Study Design:
Randomized Controlled Trial
Risk of Bias Assessment Rating:
Inclusion Criteria:
Inclusion criteria were (1) nonmalignant hypertension; (2) estimated glomerular filtration rate (eGFR) by MDRD formula 30-59 ml/min; (3) plasma total carbon dioxide (TCO2) less than 25 mmol/L and greater than 22 mmol/L; (4) macroalbuminuria; (5) able to tolerate angiotensin converting enzyme inhibition; (6) nonsmoking; (7) no diabetes or cardiovascular disease on their problem lists; (8) >2 primary care physician visits in the preceding year, showing compliance with clinic visits; (9) age >18 years and able to give consent. 961 subjects meeting study criteria were identified over 8 years, of which 108 were matched for age, sex, ethnicity, eGFR and urinary albumin and agreed to randomization.
Exclusion Criteria:
Exclusion criteria were (1) primary kidney disease or findings consistent thereof such as >3 red blood cells per high-powered field of urine or urine cellular casts; (2) history of diabetes or fasting blood glucose >110 mg/dL; (3) current pregnancy, history of malignancies, chronic infections or clinical evidence of cardiovascular disease; (4) peripheral edema or diagnoses associated with edema such as heart/liver failure or nephrotic syndrome; (5) baseline plasma [K+] >4.6 meq/L; (6) individuals taking or those who could not stop taking drugs other than angiotensin converting enzyme inhibitors that limit urine K+ excretion. The diagnosis of hypertension-associated nephropathy as the exclusive nephropathy cause was made clinically by excluding individuals with systemic diseases associated with nephropathy, nephrotic-range proteinuria, and urine abnormalities except albuminuria. Secondary causes of hypertension such as renal artery stenosis and hyperaldosteronism were excluded.
Research Purpose:
To test the hypothesis that added sodium bicarbonate (NaHCO3) or fruits and vegetables in the diet slow estimated glomerular filtration rate (eGFR) decline and reduce kidney angiotensin II (AII) levels in individuals with chronic kidney disease (CKD) stage 3 (eGFR 30-59 ml/min) and metabolic acidosis characterized by plasma total carbon dioxide (TCO2) >22 but <24 mmol/L, a range for which current guidelines do not recommend alkali treatment.
Blinding efforts:
Because receipt of fruit and vegetables could not be blinded, study subjects were randomized and the overall study was controlled but not blinded.
Study Location:
Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas
Source(s) of Funding:
Industry, University/Hospital, Not-for-profit
Please specify names of funders:
Texas Tech University Health Sciences Center, Lubbock, Texas; Inside Out Community Outreach Program; Food Bank of Lubbock, Texas; Larry and Jane Woirhaye Memorial Endowment in Renal Research, Statistics Department of Scott and White Healthcare; Academic Operations Division at Scott and White Healthcare.
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? Yes
  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? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  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? Yes
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) No
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) No
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  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%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
5. Was blinding used to prevent introduction of bias? Yes
  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.) Yes
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? No
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? ???
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
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? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  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)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? ???
  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? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes