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FL: Fluoride and the Renal System (2010)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To determine normal range of serum and urine fluoride levels in a community with a naturally low fluoride concentration in the water supply, and to investigate relationships to age, sex and renal function.

Inclusion Criteria:
  • Healthy subjects (criteria not specified)
  • Patients with renal insufficiency (criteria not specified)
  • All living in same geographical area (Catalonia, Spain).
Exclusion Criteria:

None specified.

Description of Study Protocol:

Recruitment

Volunteers with available occupational, medical, nutritional and residential histories.

Design

Non-comparative descriptive study.

Statistical Analysis

  • Comparisons between healthy subjects and patients: Student's T-test
  • Regression analysis.

 

Data Collection Summary:

Timing of Measurements

  • One-time measurement of serum and urine samples
  • Periodic measurement of water samples.

Dependent Variables

  • Serum ionic fluoride: Fluoride ion selective electrode system (ORION)
  • Urine ionic fluoride: Fluoride ion selective electrode system (ORION).

Independent Variables

Water ionic fluoride: Fluoride ion selective electrode system (ORION).

 

 

 

Description of Actual Data Sample:
  • Initial N:
    • Healthy subjects: N=250 (males=122; females=128)
    • Renal insufficiency patients: N=150 (males=84; females=66)
  • Age: 
    • Healthy subjects: 15 to 90 years
    • Renal insufficiency patients: 20 to 81 years
  • Ethnicity: Spanish
  • Location: Catalonia, Spain.
Summary of Results:

Serum and urine ionic fluoride concentration in the healthy population and in patients with renal chronic insufficiency

 

 Healthy Population Renal Patients

Statistical Significance of Group Difference

Serum fluoride concentration (mcg per L)

Mean (SD)

Range

17.5 (9.7)

(1 to 47)

58 (31)

(28 to 185)

 

P<0.005

Urine fluoride concentration (mcg per 24 hours)

Mean (SD)

Range

 671 (373)

(156 to 1,900)

 No data

 Not applicable

 

 

 

 

 

Other Findings

  • No sex-related differences were observed in the healthy group and renal patient groups
  • Serum fluoride concentration in the old-age healthy population  was higher than in the younger healthy population  (P=0.05) (comparison statistic not specified).
Age range N Mean Serum Fluoride Concentration (mcg per L)
10 to 19 25 11.3
20 to 29 28 12.8
30 to 39 45 14.7
40 to 49 41 17.6
50 to 59 41 19.6
60 to 69 40 19.7
70 to 90 30 21.3

 

  • Fluoride excretion in urine was higher in the younger healthy subjects than in older healthy subjects (P=0.05).
Age range N Mean Urine Fluoride Concentration (mcg per 24 hours)
10 to 19 25 321
20 to 29 28 660
30 to 39 45 830
40 to 49 41 862
50 to 59 41 685
60 to 69 40 640
70 to 90 30 550
  • No age-related differences were observed among renal patients
  • Water fluoride ionic concentration:
    • Fluoride concentration in public drinking water (mcg per L): 121.2 (53.6), range=90 to 200
    • Fluoride concentration of dialysis fluids (mcg per L): Five.
Author Conclusion:
  • In a healthy adult population without a program of water fluoridation, it can be expected that the serum ionic fluoride concentration would be in the range of one to 47 mcg per L, and the normal concentration for urine fluoride would be between 156 and 1,900 mcg per 24 hours 
  • Higher serum fluoride concentrations of patients with chronic renal failure are a consequence of impaired renal function and not dialysis fluid; therefore, it is important to control the intake of this element and the prolonged use of fluoridated dental products in patients with chronic renal insufficiency to avoid a risk of fluorosis.
Funding Source:
University/Hospital: Hospital Clinic and Provincial, Unversity of Barcelona
Other: not reported
Reviewer Comments:

Description of recruitment, inclusion and exclusion criteria, and statistical analyses were vague.

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) N/A
 
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? 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? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) ???
  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? N/A
  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.) Yes
  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? Yes
  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? Yes
  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? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  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
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? Yes
  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? Yes
  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? N/A
  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? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  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
  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? 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? Yes
  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? No
  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)? No
  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? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? Yes