What is the significance of the paired two-sample t-test for means comparing retrospective Hemoglobin A1c (HbA1c) and post-education HbA1c levels?

From the Guidelines

The paired t-test results show a statistically significant reduction in HgA1C levels following education intervention, with a mean decrease from 8.81% to 7.56%, which is in line with the American Diabetes Association's recommendation of an HbA1c goal of less than 7% for many nonpregnant adults 1. The improvement is statistically significant with a p-value of 0.0035 for the two-tailed test, which is well below the conventional threshold of 0.05. The positive Pearson correlation of 0.62 indicates that patients with higher initial HgA1C values tended to also have higher post-education values, though still lower than their baseline. The t-statistic of 3.21 exceeds the critical value of 2.06, confirming that the observed reduction is unlikely to have occurred by chance. Additionally, the variance decreased substantially from 6.56 to 1.89, suggesting that the education intervention not only lowered HgA1C levels but also resulted in more consistent glycemic control across patients. This analysis demonstrates that the educational intervention was effective in improving glycemic control in this group of 27 patients, which is supported by recent studies such as the one published in 2024, showing that nurse-led diabetes education interventions can lead to significant reductions in HbA1c levels 1. Some key points to consider in the management of diabetes include:

• Hemoglobin A1c should be tested at least twice per year in patients who are meeting treatment goals and quarterly in those whose therapy has changed or who are not meeting glycemic goals 1.
• A reasonable HbA1c goal for many nonpregnant adults is less than 7% 1.
• Providers might suggest more stringent HbA1c goals for selected individuals if this can be achieved without clinically significant hypoglycemia or other adverse effects 1.
• Less stringent HbA1c goals may be appropriate for patients with a history of severe hypoglycemia, limited life expectancy, advanced microvascular or macrovascular complications, extensive comorbid conditions, or long-standing diabetes 1.

From the Research

Analysis of the Paired T-Test

• The given paired t-test compares the means of retrospective HgA1C and post-education HGA1C, with a mean difference of 1.251851852.
• The t-statistic is 3.206676584, and the p-value for a one-tailed test is 0.001771798, indicating a significant difference between the two means 2.
• The paired t-test assumes that the data are normally distributed and that the variance of the two groups is equal. However, the variance of the retrospective HgA1C (6.562849003) is higher than that of the post-education HGA1C (1.887037037), which may violate this assumption.

Comparison to Studies

• A study on metformin treatment for type 2 diabetes found that metformin significantly improved glycemic control compared to placebo or sulfonylurea monotherapy 3.
• Another study compared the efficacy of metformin alone or in combination with rosiglitazone or lifestyle intervention in adolescents with type 2 diabetes, and found that metformin was effective in improving glycemic control 4.
• A study on the association between intensification of metformin treatment with insulin vs sulfonylureas and cardiovascular events and all-cause mortality found that the addition of insulin was associated with an increased risk of cardiovascular outcomes and all-cause mortality compared to sulfonylureas 5.
• A study on the power of a paired t-test with a covariate found that using the mean-centered independent variable can increase the precision of the test, and demonstrated how to compute the gains in efficiency a priori to amend the power computations for the traditional paired t-test 2.
• A tutorial on the paired t-test and beyond recommended that researchers should more consistently present the relevant characteristics of their data and explicitly consider the assumptions that apply to their statistical methods, and suggested alternative tests such as the permuted t-test for paired samples and the permuted Brunner-Munzel rank test 6.

Statistical Interpretation

• The significant p-value (0.001771798) indicates that the null hypothesis of no difference between the means of retrospective HgA1C and post-education HGA1C can be rejected, suggesting that the education intervention had a significant effect on HGA1C levels.
• The Pearson correlation coefficient (0.61591568) indicates a moderate positive correlation between the retrospective HgA1C and post-education HGA1C values.
• The t-critical value for a one-tailed test (1.70561792) is lower than the t-statistic (3.206676584), indicating that the observed difference is statistically significant.