What labs and tests are recommended for a patient suspected of having Polycystic Ovary Syndrome (PCOS)?

Recommended Laboratory Tests for PCOS Diagnosis

For patients suspected of having Polycystic Ovary Syndrome (PCOS), a comprehensive laboratory evaluation should include first-line tests of total testosterone (using LC-MS/MS), calculated free testosterone or Free Androgen Index (FAI), TSH, and prolactin, with second-line tests including 17-hydroxyprogesterone, androstenedione, DHEAS, and metabolic assessments. 1

First-Line Laboratory Tests

• Androgen Assessment:

  • Total testosterone using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for accuracy 1, 2
  • Calculated free testosterone or Free Androgen Index (FAI) - has 78% sensitivity and 85% specificity 1
  • Note: Standard immunoassays for testosterone are often inaccurate in women 2

• Exclusion of Other Disorders:

  • Thyroid-stimulating hormone (TSH) 1
  • Prolactin 1

Second-Line Laboratory Tests

When initial results are abnormal or clinical suspicion remains high:

• Additional Androgen Tests:

  • 17-hydroxyprogesterone (to rule out congenital adrenal hyperplasia) 1
  • Androstenedione (75% sensitivity, 71% specificity) 1
  • Dehydroepiandrosterone sulfate (DHEAS) (75% sensitivity, 67% specificity) 1

• Adrenal Function Tests:

  • Overnight dexamethasone suppression test or 24-hour urinary free cortisol (to rule out Cushing's syndrome) 1

Metabolic Assessment

• Glucose Metabolism:

  • 2-hour 75g oral glucose tolerance test (particularly for women with BMI >25 kg/m²) 1, 3
  • Fasting glucose/insulin ratio (ratio >4 suggests normal insulin sensitivity) 1

• Lipid Profile:

  • Total cholesterol, LDL, HDL, triglycerides 1, 3

Imaging Studies

• Transvaginal Ultrasound:
  • Should be performed between days 3-9 of menstrual cycle 1
  • Diagnostic criteria: ≥20 follicles (2-9mm) per ovary or ovarian volume ≥10ml 1
  • Evaluate endometrial thickness, follicle count, and ovarian volume 1

Special Considerations

• For Adolescents:
  • Diagnosis requires both hyperandrogenism and ovulatory dysfunction 1
  • Ultrasound not recommended until 8 years post-menarche 1
  • Anti-Müllerian Hormone (AMH) testing is not currently recommended for diagnosis 1

Diagnostic Algorithm

1. Step 1: Assess clinical features (irregular menses, hirsutism, acne)
2. Step 2: Order first-line tests (testosterone, free testosterone/FAI, TSH, prolactin)
3. Step 3: If first-line tests are abnormal or clinical suspicion remains high, order second-line tests
4. Step 4: Perform metabolic assessment (glucose tolerance test, lipid profile)
5. Step 5: Obtain transvaginal ultrasound (if appropriate)
6. Step 6: Diagnose PCOS if at least two of three criteria are present:
   • Chronic anovulation
   • Hyperandrogenism (clinical or biochemical)
   • Polycystic ovaries on ultrasound

Common Pitfalls to Avoid

• Relying solely on ultrasound findings for diagnosis 1
• Using standard immunoassays for testosterone measurement instead of LC-MS/MS 2
• Failing to exclude other disorders that can mimic PCOS 1
• Not assessing metabolic parameters, which are crucial for comprehensive management 1, 3
• Overlooking the importance of SHBG measurement, which affects free testosterone levels and reflects metabolic disturbances 2

Remember that PCOS diagnosis requires at least two of three criteria (chronic anovulation, hyperandrogenism, polycystic ovaries) with exclusion of other relevant disorders 1. The laboratory evaluation should be comprehensive to establish the diagnosis and assess associated metabolic risks.