What is needed to diagnose polycystic ovary syndrome (PCOS)?

Diagnosing Polycystic Ovary Syndrome (PCOS)

The diagnosis of PCOS requires at least two of three Rotterdam criteria: chronic anovulation, hyperandrogenism (clinical or biochemical), and polycystic ovaries on ultrasound, with exclusion of other disorders. 1

Diagnostic Criteria

The Rotterdam criteria for PCOS diagnosis include:

1. Chronic Anovulation/Oligo-ovulation

   • Irregular menstrual cycles (>35 days) or fewer than 8 menstrual cycles per year
   • Cycle length slightly longer than normal (32-35 days) or slightly irregular (32-36 days) requires assessment for ovulatory dysfunction 1

2. Hyperandrogenism

   • Clinical signs:

     • Hirsutism (gradual onset, intensifies with weight gain)
     • Acne (severe or resistant to treatment)
     • Alopecia (vertex, crown, or diffuse pattern; severe cases may show bitemporal hair loss)

   • Biochemical markers (recommended tests):

     • Free testosterone (most sensitive marker) - ideally measured through equilibrium dialysis techniques
     • Total testosterone
     • Free Androgen Index (FAI) - 78% sensitivity, 85% specificity
     • Androstenedione (A4) - 75% sensitivity, 71% specificity
     • DHEAS - 75% sensitivity, 67% specificity 1

3. Polycystic Ovarian Morphology (PCOM) on Ultrasound

   • ≥20 follicles (2-9mm) per ovary OR
   • Ovarian volume ≥10ml 1
   • Note: Ultrasound findings alone are not sufficient for diagnosis and must be correlated with clinical and biochemical findings 2, 1

Laboratory Workup

To confirm PCOS diagnosis and exclude other disorders:

• First-line laboratory tests:

  • Total testosterone and free testosterone using mass spectrometry (highest diagnostic accuracy) 1
  • Thyroid-Stimulating Hormone (TSH)
  • Prolactin
  • 17-hydroxyprogesterone (to rule out congenital adrenal hyperplasia)
  • Anti-Müllerian hormone (useful for determining PCOS diagnosis) 1, 3

• Additional tests to exclude other disorders:

  • Overnight dexamethasone suppression test or 24-hour urinary free cortisol (to rule out Cushing's syndrome)
  • Fasting lipid profile
  • Fasting glucose/insulin ratio
  • 2-hour 75g oral glucose tolerance test (OGTT) for patients with BMI >25 kg/m² 1

Ultrasound Evaluation

• Transvaginal ultrasound is preferred for adult women
• Transabdominal/transrectal ultrasound for adolescents 2
• Key measurements:
  • Follicle number per whole ovary (FNPO) - most accurate ultrasonographic marker 2
  • Ovarian volume (OV)
  • Follicle number per single cross-section/slice (FNPS) - alternative when accurate total follicle counts aren't possible 2

Special Considerations

Adolescents

• Diagnosis is challenging in adolescents due to overlap with normal pubertal changes
• Ultrasound is not recommended as first-line investigation in females <17 years 3
• Persistent oligomenorrhea 2-3 years post-menarche suggests underlying ovarian or adrenal dysfunction 3
• Diagnosis should be based on oligomenorrhea and/or biochemical evidence of oligo/anovulation 3

Common Pitfalls to Avoid

1. Relying solely on ultrasound findings - PCOM can be present in women without PCOS; diagnosis requires correlation with clinical and biochemical findings 1

2. Using inappropriate laboratory tests - Free testosterone levels are more sensitive than total testosterone for establishing androgen excess 3

3. Not excluding other disorders - Conditions that mimic PCOS must be ruled out, including:

   • Congenital adrenal hyperplasia
   • Cushing's syndrome
   • Androgen-producing tumors
   • Hyperprolactinemia
   • Thyroid disorders 4, 3

4. Timing of hormone measurements - Ideally taken during early follicular phase in menstruating women 1

5. Not recognizing geographic variations - Geographic differences may influence PCOS phenotypes and diagnostic accuracy of ultrasound markers 2

By following these comprehensive diagnostic criteria and avoiding common pitfalls, clinicians can accurately diagnose PCOS and develop appropriate management strategies to address associated health risks.