Calcium and Vitamin D Study Analysis

Questions and Answers

What was the reason given for questioning the prognostic balance between the intervention and control groups?

Randomization was not possible

Participants were not blind to treatment

No information on baseline characteristics was available (correct)

The sample size was too small

Which factor indicates a problem with randomization in the study?

Participants were not informed of their group assignment

There was no mention of the allocation concealment process (correct)

The intervention groups had similar prognoses initially

Computer generated block randomization was used

What aspect of blinding in the study was highlighted as insufficient?

Blinding was maintained throughout the trial

All participants were aware of the treatment

Data analysts were not included in the blinding

Patients were likely blind but not staff (correct)

What percentage of participants completed the follow-up process?

87% Signup and view all the answers

In regard to the intent-to-treat (ITT) methodology, what was observed about the analysis of participants?

They were analyzed based on initial group allocation Signup and view all the answers

What was a noted limitation regarding the blinding of the trial?

There was potential unblinding of nurses and analysts Signup and view all the answers

Based on the assessment of prognostic balance, what was concluded at the study's completion?

Prognostic balance was not likely retained Signup and view all the answers

Which of the following was considered a significant omission in the study?

Baseline characteristic data presentation Signup and view all the answers

What was concluded regarding the influence of lack of allocation concealment on the study results?

It raises suspicion about group assignments Signup and view all the answers

Why is the potential for early stopping of the trial significant?

It affects the statistical analysis validity Signup and view all the answers

Study Notes

Overall Study Findings

Calcium only group exhibited a 47% relative risk reduction compared to placebo, exceeding the 20% threshold but lacked statistical significance, suggesting results may be due to chance.
The calcium vitamin D group showed a 4% absolute risk reduction, while the calcium only group had a 3.1% absolute risk reduction.
Despite significant relative risk reductions, large confidence intervals raised concerns regarding clinical importance and precision.

Confidence Intervals and Treatment Effects

Confidence interval for calcium and vitamin D ranged from 0.2 to 0.82 (P=0.013), indicating statistical significance but poor precision.
Calcium only group had a confidence interval of 0.27 to 1.03 (P=0.063), suggesting results were imprecise and not statistically significant.

Study Validity and Analysis

Significant number of losses (over 5%) could affect study results; no details provided on differential losses to follow-up.
Patients were not analyzed in the groups they were originally assigned; only a subset completed the study.
Intention-to-treat (ITT) analysis was not performed due to issues with maintaining original group assignments.

Clinical Significance of Results

Despite observing a 60% reduction in cancer incidence for the vitamin D and calcium group compared to placebo, confidence intervals ranged from an 80% reduction to a 17% reduction, raising questions about clinical significance.
Results indicating calcium alone do not provide evidence for improved cancer outcomes beyond chance.

Randomization and Prognostic Balance

Randomization was conducted using computer-generated block randomization, ensuring initial equal distribution among groups.
Lack of information regarding concealment of randomization process and absence of baseline characteristics table hinder the assumption of successful randomization.
Insufficient information suggests groups may not have been prognostically balanced before or during the study.

Study Progress and Follow-Up

Follow-up completion was low at 87%, potentially impacting the reliability of the results.
Although patients were likely blinded, lack of detail on blinding for other personnel (nurses, analysts) raises concerns about the integrity of the study process.
Prognostic balance is likely not retained throughout the trial due to insufficient follow-up and blinding concerns.

Description

This quiz explores the findings of a study on calcium and vitamin D, focusing on the risk reduction compared to placebo. Analyze the statistical significance and risk difference highlighted in the results. Test your understanding of the implications of confidence intervals and absolute risk reduction in clinical research.