Objective:

To investigate the synergistic effect of vitamin D deficiency and metabolic disorders on albuminuria in type 2 diabetes mellitus (T2DM) patients and to construct a validated risk stratification nomogram.

Approach:

• Study Design: A cross-sectional study was conducted on 507 T2DM patients, divided into normal albumin and albuminuria groups.
• Data Collection: Serum 25-hydroxyvitamin D levels were measured, and various statistical analyses were performed to identify predictors of albuminuria.
• Nomogram Construction: A nomogram was constructed and validated using concordance index, calibration curves, and decision curve analysis.

Key Findings:

• 83.0% of patients had vitamin D deficiency, significantly higher in the albuminuria group (91.8%).
• ACR levels were negatively correlated with 25-OH-VD levels (ρ=-0.326, P < 0.001).
• Vitamin D deficiency and elevated HbA1c had a significant positive synergistic effect on albuminuria.
• Independent predictors identified included age, BMI, HbA1c, 25-OH-VD, LDL-C, eGFR, and the vitamin D deficiency × HbA1c interaction term.
• The nomogram showed excellent discriminative ability with C-indices of 0.882 in the training set and 0.858 in the validation set.

Interpretation:

Vitamin D deficiency is prevalent in T2DM patients and synergizes with elevated HbA1c to drive albuminuria progression.

Limitations:

• The study is cross-sectional, limiting causal inferences.
• The sample was taken from a single hospital, which may affect generalizability.

Conclusion:

The constructed nomogram may serve as a tool for risk assessment in T2DM patients.