EAL

FL: Fluoride and the Renal System (2010)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To comprehensively investigate pathogenic mechanisms for two types of flurosis incorporating essential elements of bone mineral metabolism, nephrologic parameters and skeletal dynamics at a microscopic level on patients with fluorotoxic metabolic bone disease.

Inclusion Criteria:

Patients with fluorotoxic metabolic bone disease (FMBD).

Exclusion Criteria:

None specified.

Description of Study Protocol:

Design

Cross-sectional study.

Intervention

Detailed clinical workup
Radiological evaluation, including skeletal survey of forearm, hands, skull, chest, dorsolumbar spine, pelvis and bones of the lower extremities
Dietary intake of calcium, phosphorus and phytates: Diet recall of previous five to seven days
Routine hospital diet at hospitalization (approximately 450mg Ca per day)
Day three: Serum samples for three consecutive days; 24-hour urine collections.

Statistical Analysis

Correlational analysis of individual biochemical parameters of group: Spearman correlation coefficient
Correlations between stratified groups based on creatinine clearance: Kruskal-Wallis test
Correlations between controls and FMBD patients: Mann-Whitney U test.

Data Collection Summary:

Timing of Measurements

Five to seven days prior to admission: Diet recall for dietary intake of calcium, phosphorus and phytates
Day three, four and five of observation: Venous blood samples and 24-hour urine collections.

Dependent Variables

Clinical exam
Radiological skeletal survey of forearm, hands, skull, chest, dorsolumbar spine pelvis and bones of lower extremities
Serum calcium, phsphorus alkaline phosphatase (SAP), creatinine, protein, 25-hydroxy vitamin D, 24-di-hydroxy-vitamin D2, and parathyroid hormone mid-molecule (PTH-MM): three-day venous blood samples
Urinary calcium, phosphorus, creatinine, fluoride, urniary calcium to creatinine (Ca/Cr) ratio, phosphorus excretion index (PEI) and endogenous creatinine clearance (Cr:Cl): 24-hour urine collections
Clinical features of osteomalcia: Osteomalacia discriminate index
Bone fluoride content: Bone biopsy specimens (in subset and in controls).

Independent Variables

Fluoride ingestion.

Description of Actual Data Sample:

Initial N: N=24 (males, 11; females, 13)
Attrition (final N): N=24
Age: Mean±SD, 31±16 years
Ethnicity: Indian subcontinent
Location: India.

Summary of Results:

Clinical

Daily dietary calcium intake: 300mg to 800mg per day
One or more bone deformities with bone pains (79%) and proximal muscle weakness (58%) present in whole cohort
Dental fluorosis in 37.5% of patients.

Radiological

More than one feature coexisted in each patient:

Osteosclerosis: 96%
Ligamentous calcification: 50%
Dental mottling: 38%
Pseudofracture: 33%
Osteopenia and coarse trabecular pattern: 21%.

Bone Fluoride Content

Elevated bone fluoride content (BFC) in FMBD patients confirms chronic fluoride ingestion: BFC of FMBD patients was 0.63±0.56%, in normal controls it was 0.15±0.07%; P<0.05
There is more fluoride ingestion in India, presumably through drinking water, compared to France; BFC of controls in India was 0.15±0.07%, BFC of controls in France was 0.05±0.03%, P< 0.05.

Biochemical

Values are expressed as mean±SD unless otherwise specified.

FMBD patients had hypocalcemia and raised SAP with normal serum phosphorus
- Serum Ca (mean±SD) = 2.18±0.20mmol per L (normal range, 2.25 to 2.75mmol per L). 58% had hypcalcemia.
- Serum P (mean±SD) = 1.16±0.34mmol per L (normal range, 0.8 to 1.5mmol per L)
  - Low serum P: 25% of patients
  - Normal serum P: 58% of patients
  - Raised serum P: 17% of patients
  - 36% had both hypocalcemia and hypophosphatemia
- Serum SAP (mean±SD) = 264.5±222.5IU per L (normal range, 21 to 92IU)
Mean serum creatinine = 85.42 + 57umol per L (normal range, 53.04 to 141.44umol per L); correlation between serum creatinine and PEI was R, 0.76, P<0.0003
CrCl:
- 71% of patients had compromised CrCl (48±26ml per minute)
- 29% of patients had normal CrCl (110±11.34ml per minute)
- CrCl values of patients spanned from normal (more than 90ml per mt) to very low (less than 29ml); progresively declining CrCl was correlated with progressively increasing renal loss of Ca and P, indicated by increased Ca/Cr ratio and PEI (but normal serum P with high PEI)
- PEI in patients with normal CrCl was low (0.09±0.05) compared to those who had compromised CrCl (0.32±0.29) (P<0.05)
- No significant increase in serum P with decreasing CrCl when stratified by CrCl; In the most severely impaired CrCl patients (less than 29ml per minute) with azotemia, serum P remained normal (1.11±0.29mmol per L)
- Renal phosphorus loss increased with declining CrCl: R=-0.82, P<0.0001
- Correlation between CrCl and serum creatinine: R=- 0.83, P<0.0001
PEI:
- Using upper cut-off level of 0.09 as normal PEI, 29% of fluorotic patients had normal PEI; 71% had high PEI
- Correlation between serum creatinine and PEI: R=0.76, P<0.0003)
- Correlation between urinary Ca/Cr ration and PEI: R=-0.69, P<0.005)
- Correlation between Cr/Cl and PEI: R=-0.82, P<0.0001
Vitamin D (25[OH] D) deficiency was present in both FMBD patients and normal controls:
- FMBD: 4.34±13.68ng per ml
- Normal controls: 8.07±3.29ng per ml
- 16/24 FMBD patients had serum 25 (OH) D below the lowest limit of normal value
1,25 [OH]₂D:
- Normal control (N=20) - 39±12.11pg per ml (normal range, 15pg to 60pg per ml)
- FMBD: 63.3±36pg per ml (P<0.0001)
PTH-MM:
- Normal controls: 48.8±9.5pmol per L (normal range, 29pmol to 85pmol per L)
- FMBD: 50.68±32.34 (P=NS).

Bone Histomorphometry

In FMBD patients (N=4), significant increase in osteoid volume, surface and thickenss:

Hypomineralized lacunae and interstitial formation defects
Only lamellar bone in all biopsy specimens
Compared to controls from India, FMBD patients had significant increase in osteoid volume, surface and thickness.

Other Findings

In FMBD patients:

Serum fluoride: 0.16±34.34ppm (normal = 0.02ppm)
Urine fluoride: 2.57±3.36ppm (normal = 0.1ppm)
Water fluoride content: 3.5±4.6 ppm (normal = 1.0ppm).

Author Conclusion:

Fluoride intoxication plays an important role in the pathogenesis of the unique osteo-renal syndrome.

Funding Source:

Government:

Department of Biotechnology, Ministry of Science and Technology, Government of India

Reviewer Comments:

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?	Yes
	2.2.	Were criteria applied equally to all study groups?	N/A
	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)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	No
	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.)	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?		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?	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?		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?	Yes
	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?	N/A
	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?	N/A
	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?	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?	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?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes