In a 54-year-old woman undergoing preoperative evaluation for ankle surgery, who has type 2 diabetes mellitus on metformin with a hemoglobin A1c of 6.85% measured several months ago, which test should be ordered now: repeat hemoglobin A1c, prothrombin time/international normalized ratio, transthoracic echocardiogram, or high‑sensitivity cardiac troponin?

No Additional Testing Required

Based on current guidelines, you should not order any of these tests for this patient. Her diabetes is well-controlled with an HbA1c of 6.85% measured several months ago, and she is undergoing low-risk ankle surgery.

Rationale for Each Test Option

a) Hemoglobin A1c - NOT INDICATED

The most recent perioperative diabetes guidelines establish clear parameters for when repeat HbA1c testing is needed:

• The 2025 ADA guidelines 1 and 2024 AHA/ACC guidelines 2 recommend preoperative HbA1c testing only if it has not been performed in ≥3 months
• Your patient had HbA1c measured "several months ago" - if this was within 3 months, repeat testing is not indicated
• The target HbA1c for elective surgeries is <8% 3, 1, 4, 3, and her value of 6.85% is well below this threshold
• Even if the test was >3 months ago, her excellent control on metformin monotherapy and the low-risk nature of ankle surgery make urgent optimization unlikely to change management

Key guideline statement: "The A1C goal for elective surgeries should be <8% (<64.0 mmol/L) whenever possible" 1. Her current value meets this target.

b) Prothrombin Time/INR - NOT INDICATED

• PT/INR is only indicated preoperatively in patients with:

  • Known bleeding disorders
  • Liver disease
  • Active anticoagulation therapy
  • High-risk surgeries with significant bleeding risk

• The 2023 ESC quality indicators 5 recommend checking coagulation profiles in intermediate- and high-risk patients, but ankle surgery is considered low-risk

• Your patient is only on metformin, which does not affect coagulation

• Routine coagulation screening in healthy patients undergoing low-risk surgery is not supported by guidelines and represents low-value care

c) Transthoracic Echocardiogram - NOT INDICATED

Echocardiography is not routinely recommended for preoperative evaluation unless specific indications exist:

• The 2014 ESC/ESA guidelines 6 and 2023 ESC quality indicators 5 recommend echocardiography only in:

  • High-risk patients with ongoing symptoms of heart failure
  • Severe valvular lesions during high-risk surgery
  • Patients at increased risk of significant hemodynamic disturbances

• Ankle surgery is low-risk and does not create significant hemodynamic stress

• Your patient has no mentioned cardiac symptoms or history

• The 2025 ADA guidelines 1 recommend "preoperative risk assessment for people with diabetes who are at high risk for ischemic heart disease and those with autonomic neuropathy or renal failure" - but this refers to clinical assessment, not routine echocardiography

d) High-Sensitivity Cardiac Troponin - NOT INDICATED

While emerging evidence shows associations between troponin and diabetes complications, routine preoperative troponin screening is not recommended for low-risk surgery:

• The 2023 ESC quality indicators 5 recommend troponin measurement preoperatively and at 24-48 hours postoperatively only in "intermediate- and high-risk patients undergoing high-risk NCS"
• Ankle surgery does not meet the high-risk surgery threshold
• Research shows elevated hs-cTnI predicts long-term cardiovascular events in diabetics 7, 8, 9, but this is for risk stratification, not routine preoperative screening for low-risk procedures
• The 2024 AHA/ACC guidelines 2 do not recommend routine troponin screening for low-risk surgeries

What You SHOULD Do

Focus on perioperative glucose management 3, 1, 4, 3:

1. Hold metformin on the day of surgery - this is a Class I recommendation across all guidelines 3, 1, 4, 3, 2
2. Target perioperative blood glucose of 100-180 mg/dL 1, 4, 3
3. Monitor blood glucose every 2-4 hours while NPO and dose with rapid-acting insulin as needed 3, 1, 3
4. Resume metformin postoperatively once oral intake is established and renal function is stable 10

Common Pitfalls to Avoid

• Over-testing: Ordering tests "just to be safe" in low-risk patients increases costs without improving outcomes
• Delaying surgery for HbA1c optimization: With HbA1c of 6.85%, this patient is already optimized. The threshold for concern is HbA1c ≥8% 3, 1, 4, 3
• Continuing metformin through surgery: This increases risk of lactic acidosis, particularly with contrast agents or perioperative stress 10
• Ignoring SGLT2 inhibitors: If she were on these medications, they must be stopped 3-4 days before surgery 3, 1, 4, 3, 2