Diabetes Risk Calculator

San Antonio Diabetes Prediction Model (Stern Formula)

The San Antonio Diabetes Prediction Model (SADPM), commonly referred to as the Stern Diabetes Model, is a clinically validated multivariate risk assessment algorithm developed by Dr. Michael P. Stern and colleagues in 2002. Published in the Annals of Internal Medicine from the longitudinal San Antonio Heart Study cohort, this tool estimates an individual's absolute percentage risk of developing type 2 diabetes mellitus over a 7.5-year window.

Traditional screening often relied solely on the 2-hour oral glucose tolerance test (OGTT), which can be time-consuming and inconvenient. The Stern model provides exceptional discriminative accuracy (C-statistic > 0.84) using standard non-invasive demographic factors and routine baseline laboratory values:

• Age: Age in completed years.
• Biological Sex: Females receive an adjusted weighting due to hormonal and metabolic distribution factors.
• Ethnicity: Accounts for elevated baseline susceptibility among Mexican American and Hispanic populations.
• Fasting Plasma Glucose (FPG): Fasting blood sugar level (mg/dL or mmol/L).
• Systolic Blood Pressure: Blood pressure in mmHg reflecting vascular resistance.
• HDL Cholesterol: High-density lipoprotein (protective cholesterol) in mg/dL or mmol/L.
• Body Mass Index (BMI): Weight relative to height (kg/m²), measuring adiposity and insulin resistance.
• Family History of Diabetes: Presence of diabetes in a first-degree relative (parent or sibling).

Mathematical Formula and Calculation

The probability of developing type 2 diabetes over 7.5 years is calculated using the logistic regression equation:

$$P(\text{Diabetes}) = \frac{1}{1 + e^{-x}} \times 100\%$$

Where the linear log-odds predictor \(x\) is defined as:

$$x = -13.415 + (0.028 \times \text{Age}) + (0.661 \times \text{Sex}) + (0.412 \times \text{Ethnicity}) + (0.079 \times \text{FPG}) + (0.018 \times \text{SBP}) - (0.039 \times \text{HDL}) + (0.070 \times \text{BMI}) + (0.481 \times \text{FamilyHistory})$$

Variable assignments:

• \(\text{Sex} = 1\) if Female, \(0\) if Male
• \(\text{Ethnicity} = 1\) if Mexican American / Hispanic, \(0\) otherwise
• \(\text{FPG}\) = Fasting plasma glucose in mg/dL (convert from mmol/L by multiplying by 18.0182)
• \(\text{SBP}\) = Systolic blood pressure in mmHg
• \(\text{HDL}\) = HDL cholesterol in mg/dL (convert from mmol/L by multiplying by 38.67)
• \(\text{BMI}\) = Body mass index in kg/m²
• \(\text{FamilyHistory} = 1\) if present in parent/sibling, \(0\) if absent

Risk Stratification and Clinical Action

Based on clinical practice guidelines from the American Diabetes Association (ADA) and clinical epidemiology recommendations, the calculated 7.5-year risk is grouped into actionable tiers:

Related Metabolic and Cardiovascular Calculators

Explore related clinical assessment and metabolic health tools:

• Blood Sugar Converter to translate between US (mg/dL) and international (mmol/L) units.
• QUICKI Calculator for quantitative insulin sensitivity check index calculation.
• HOMA-IR Calculator for homeostatic model assessment of insulin resistance and beta-cell function.