CD: Bone Density (2006)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To investigate the prevalence of osteopenia; to identify the relationship between bone mineral density, serum calcium, and parathyroid hormone levels; and to determine the effect of gluten-free diet on bone mineral density in children with celiac disease.
Inclusion Criteria:
Diagnosis of celiac disease made according to the criteria of the European Society for Pediatric Gastroenterology, Hepatology and Nutrition, by intestinal biopsy (villous atrophy in the duodenal or jejunal mucosa).  All patients had antiendomysium antibodies.  After gluten withdrawal, a full clinical remission was observed. 
Exclusion Criteria:
Presence of other diseases known to affect bone mineral density.  None received hormone or dietary supplements except iron and zinc.  Control subjects were excluded if they had a history of chronic illness, and if they had taken any vitamin preparation, hormone or calcium supplement regularly.
Description of Study Protocol:

Recruitment

 

Design

Nonrandomized Clinical Trial.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

Gluten-free diet.

Statistical Analysis

The results of biochemical parameters and the bone mineral density were expressed as mean values +/- SD.  Bone mineral density values were expressed as Z scores, defined as the deviation of the individual value from the mean valueof each reference group expressed in units of the standard deviation.  In newly diagnosed celiac patients, the Z score values of the patients with and without GI symptoms were compared with each other.  The Wilcoxon signed rank test and the Mann-Whitney U test were used when comparing paired and non-paired data respectively.  Correlation was evaluated by the Spearman rank test.  Differences were regarded as significant at P < 0.05. 

Data Collection Summary:

Timing of Measurements

Bone mineral density, bone mineral content and biochemical parameters were determined upon study entry and at 12 months in celiac patients.  Values compared to healthy controls.

Dependent Variables

  • Concentrations of calcium, phosphorus and alkaline phosphatase determined with Hitachi 717 autoanalyzer and calcium values corrected for albumin where appropriate.  Serum calcium and phosphate concentrations were measured by timed-endpoint biuret method and total alkaline phosphatase by enzymatic rate method.
  • Intact parathyroid hormone measured by chemiluminescent enzyme assay
  • Bone mineral density and bone mineral content measured at the lumbar spine (L1-4) using dual energy radiograph bone densitometer

Independent Variables

  • Gluten-free diet.  Compliance ascertained by measuring serum antiendomysium antibodies during follow-up.

Control Variables

 

Description of Actual Data Sample:

Initial N: 32 patients with celiac disease in childhood, divided into 2 groups:  recently diagnosed (n=16, 7 females, 9 males) and strict diet followers (n=16, 4 females, 12 males), and 82 healthy age- and sex-matched controls (31 females, 51 males), 3 controls per subject.

Attrition (final N):  Same as above.

Age:  Recently diagnosed:  mean age 10.6 years, range 3.5 - 17 years.  Strict diet followers:  mean age 11.5 years, range 5 - 18 years.  Controls:  mean age 9.8 +/- 2.3 years. 

Ethnicity:   Not mentioned.

Other relevant demographics:  Recently diagnosed:  mean duration of symptoms before diagnosis was 3.2 years (range 1.5 - 6 years).  Strict diet followers:  treated with gluten-free diet for a mean time of 40.4 months (range 19 - 84 months). 

Anthropometrics 3 age- and sex-matched controls per subject.

Location:  Ankara, Turkey  

 

Summary of Results:

 

Baseline 1 Year Significance P-value
Recently Diagnosed -BMD 0.51 +/- 0.11 0.56 +/- 0.09 0.041
Recently Diagnosed -BMC 13.66 +/- 6.39 15.57 +/- 4.82 0.006
Recently Diagnosed - Z Score -1.55 +/- 1.36 -0.38 +/- 1.19 0.028
Strict Diet Followers - BMD 0.58 +/- 0.16

0.64 +/- 0.22

0.005

Strict Diet Followers - BMC

18.29 +/- 8.72

22.59 +/- 12.77

0.008

Strict Diet Followers - Z Score

-0.67 +/- 0.85

-0.37 +/- 0.98

0.011

Other Findings

Bone mineral density and bone mineral content values in patients with recent diagnosis were found to be significantly lower than the control group (p < 0.05).  The bone mineral density values in patients with recent diagnosis were significantly increased after a gluten-free diet for 1 year. 

Osteopenia (Z score lower than -1.0) was found in 50% of patients with celiac disease (recently diagnosed:  62.5%, strict diet followers: 37.5%).

At 1 year follow-up, the percentage of patients who had osteopenia decreased considerably - 50% of newly diagnosed and 33.3% of strict diet followers who had osteopenia at the beginning of the study showed normal Z score after 1 year of gluten-free diet.  However, osteopenia was not always resolved with the gluten-free diet, and this was especially true in patients without gastrointestinal manifestation. 

In patients with recent diagnosis, the mean calcium level was found to be lower than the patients who follow their diet strictly and controls (P < 0.05), whereas no significant difference was found between the groups with respect to serum phosphate, alkaline phosphatase, and intact parathormone levels.

In the newly diagnosed patients, there was a positive correlation between calcium level and bone mineral density and bone mineral content (r=0.37, P < 0.05).

Author Conclusion:
Bone mineral density is almost invariably low in newly diagnosed celiac patients in childhood.  We therefore recommend that bone mineral density should be evaluated in patients with celiac disease.  Although osteopenia complicates celiac disease during childhood, strict gluten avoidance promotes a significant increase in bone mineral density.  However, values still remained markedly low after 1 year of follow-up in some patients, especially those without GI manifestation.  These patients should be followed for longer periods of time with yearly bone mineral density evaluation, as 1 year of diet therapy was found to be insufficient for osteopenia to be resolved.
Funding Source:
University/Hospital: Ondokuz Mayis University, Ankara University (both Turkey)
Reviewer Comments:
Compliance measured through antibodies.  3 controls per subject.
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? 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.) 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.) 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? 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? Yes
  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? N/A
  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.) N/A
  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? 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? Yes
  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? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  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? 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