What labs are recommended for a patient with suspected Polycystic Ovary Syndrome (PCOS)?

Laboratory Testing for Suspected Polycystic Ovary Syndrome (PCOS)

First-line laboratory tests for PCOS diagnosis should include total testosterone, free testosterone, thyroid-stimulating hormone (TSH), prolactin, and 17-hydroxyprogesterone. 1

Core Diagnostic Tests

The diagnosis of PCOS requires a comprehensive laboratory evaluation to confirm hyperandrogenism and exclude other disorders. Based on high-quality evidence, the following tests should be ordered:

Hormonal Assessment

• Androgen Profile:

  • Total testosterone (elevated in 70% of PCOS cases, >2.5 nmol/L) 1
  • Free testosterone or Free Androgen Index (FAI) (sensitivity 78%, specificity 85%) 1
  • Androstenedione (A4) (sensitivity 75%, specificity 71%) 1
  • DHEAS (sensitivity 75%, specificity 67%) 1

• Pituitary Hormones:

  • LH and FSH (elevated LH/FSH ratio >2 is common in PCOS) 1
  • Prolactin (to rule out hyperprolactinemia) 1
  • TSH (to exclude thyroid dysfunction) 1

• Other Hormones:

  • 17-hydroxyprogesterone (to rule out congenital adrenal hyperplasia) 1
  • Progesterone (often low <6 nmol/L in PCOS due to anovulation) 1

Metabolic Assessment

Given the high prevalence of metabolic abnormalities in PCOS, the following tests are essential:

• Glucose Metabolism:

  • 2-hour 75g oral glucose tolerance test (OGTT) (preferred over HbA1c or fasting glucose) 2
  • Fasting insulin (to calculate glucose/insulin ratio; ratio >4 suggests insulin resistance) 1

• Lipid Profile:

  • Complete fasting lipid panel (total cholesterol, LDL, HDL, triglycerides) 2

Additional Considerations

• Calculated bioavailable testosterone has a sensitivity of 76% and specificity of 83% for diagnosing PCOS, with a cutoff of 0.78 nmol/L 1
• Both normal weight and obese PCOS patients should be screened for metabolic syndrome components 3
• The Rotterdam criteria require two of three features for diagnosis: chronic anovulation, hyperandrogenism, and polycystic ovaries on ultrasound 1

Common Pitfalls to Avoid

1. Underutilization of metabolic screening: Studies show that 22.3% of gynecologists don't order any screening tests at initial visits for PCOS patients 2

2. Using inappropriate glucose tests: Many providers use HbA1c (51%) or fasting glucose (42.7%) instead of the recommended OGTT (only 7% use this) 2

3. Failing to exclude other disorders: PCOS is a diagnosis of exclusion, requiring thorough evaluation to rule out other causes of hyperandrogenism 3

4. Overlooking non-obese patients: Up to 50% of PCOS patients are normal weight but may still have metabolic abnormalities requiring screening 3

5. Missing follow-up testing: Patients should undergo repeat metabolic screening every 2-5 years for glucose tolerance and every 2 years for lipid profile 2

By following this comprehensive laboratory approach, clinicians can accurately diagnose PCOS and identify associated metabolic abnormalities that require management to prevent long-term complications.