What follow-up tests should be ordered for a patient recently diagnosed with Type 1 Diabetes Mellitus (T1DM)?

Follow-Up Testing for Newly Diagnosed Type 1 Diabetes

For a patient recently diagnosed with Type 1 Diabetes Mellitus, order the following initial laboratory tests: HbA1c (if not already done for diagnosis), fasting lipid panel, urine albumin-to-creatinine ratio (if ≥5 years post-puberty), serum creatinine, thyroid-stimulating hormone (TSH) with antithyroid peroxidase and antithyroglobulin antibodies, and IgA tissue transglutaminase antibodies with total serum IgA level to screen for celiac disease. 1, 2

Core Metabolic and Glycemic Monitoring

HbA1c Baseline

• Establish baseline HbA1c if not already measured during diagnosis to guide treatment targets and monitor glycemic control 1
• Target HbA1c <7.0% for most patients, though this should be individualized based on hypoglycemia risk 1
• HbA1c will be repeated every 3 months during treatment adjustments 1

Renal Function Assessment

• Measure serum creatinine at diagnosis to establish baseline kidney function 1
• For Type 1 diabetes, annual urine albumin-to-creatinine ratio (uACR) testing begins 5 years after diagnosis in pubertal or post-pubertal individuals, not at initial diagnosis unless the patient has already had diabetes for ≥5 years 1
• Use first morning void urine sample for uACR when annual screening begins 1

Critical Pitfall: Do not start annual albuminuria screening immediately at diagnosis in Type 1 diabetes—this is only for Type 2 diabetes. For Type 1, wait until 5 years post-diagnosis if the patient is pubertal/post-pubertal. 1

Cardiovascular Risk Assessment

Lipid Panel

• Obtain fasting lipid profile at diagnosis including total cholesterol, HDL cholesterol, triglycerides, and calculated LDL cholesterol 1
• This establishes baseline cardiovascular risk, as diabetes significantly increases atherosclerotic disease risk 1
• If lipid values are at low-risk levels (LDL <100 mg/dL, HDL >50 mg/dL, triglycerides <150 mg/dL), repeat every 2 years 1

Autoimmune Comorbidity Screening

Thyroid Disease

• Measure TSH when clinically stable or soon after optimizing glycemia at diagnosis 1, 2
• Test for antithyroid peroxidase and antithyroglobulin antibodies at diagnosis, as these are more predictive of future thyroid dysfunction than TSH alone 1, 2
• Antithyroid peroxidase antibodies are more predictive than antithyroglobulin antibodies in multivariate analysis 1
• If normal and antibodies negative, recheck TSH every 1-2 years; if antibodies positive, monitor more frequently 1

Rationale: Thyroid dysfunction occurs in a significantly higher proportion of Type 1 diabetes patients compared to the general population, with hypothyroidism being most common 1, 2

Celiac Disease

• Screen with IgA tissue transglutaminase (tTG) antibodies plus total serum IgA level soon after diagnosis 1, 2, 3
• If IgA deficient, use IgG tTG and deamidated gliadin antibodies instead 1
• Celiac disease occurs in 1.6-16.4% of Type 1 diabetes patients versus 0.3-1% in the general population 1
• Repeat screening within 2 years of diabetes diagnosis, then again after 5 years 1

Critical Pitfall: Always measure total serum IgA when ordering IgA tTG antibodies, as IgA deficiency will cause false-negative results. 1

Additional Considerations at Diagnosis

Urinalysis

• Perform urinalysis for ketones, protein, and sediment at initial evaluation 1
• This helps assess for diabetic ketoacidosis at presentation and establishes baseline renal status 1

Electrocardiogram

• Consider ECG in adults if clinically indicated based on cardiovascular risk factors 1

Ophthalmologic Referral

• Arrange dilated comprehensive eye examination within 5 years after onset for Type 1 diabetes patients 1
• This is not an immediate laboratory test but should be coordinated at diagnosis 1

Tests NOT Recommended at Diagnosis

Genetic Testing

• Routine determination of genetic markers (HLA genes, SNPs) has no value for diagnosis or management of clearly diagnosed Type 1 diabetes 1
• Reserve genetic testing only for uncertain cases where phenotypic overlap between Type 1 and Type 2 exists 1

Islet Autoantibodies

• Do not routinely order islet autoantibodies (GAD, IA-2, ZnT8, IAA) if Type 1 diabetes diagnosis is clinically clear based on presentation with acute symptoms, marked hyperglycemia, and young age 1
• Autoantibody testing is reserved for cases with diagnostic uncertainty or phenotypic overlap with Type 2 diabetes 1, 2, 4

C-Peptide

• Not recommended routinely at diagnosis for typical Type 1 diabetes presentation 1
• Reserve for uncertain cases or research purposes 1

Ongoing Monitoring Schedule Summary

After initial testing:

• HbA1c: Every 3 months during treatment optimization 1
• Lipid panel: Every 2 years if at goal 1
• TSH: Every 1-2 years if normal and antibody-negative; more frequently if antibodies positive 1
• Celiac screening: Repeat within 2 years, then at 5 years 1
• Urine albumin: Annually starting 5 years post-diagnosis (if pubertal/post-pubertal) 1
• Serum creatinine: Monitor when indicated clinically, especially if albuminuria develops 1