What are the diagnostic criteria for Polycystic Ovary Syndrome (PCOS)?

Diagnostic Criteria for Polycystic Ovary Syndrome (PCOS)

The diagnosis of PCOS requires two out of three criteria according to the Rotterdam criteria: oligo- or anovulation, clinical and/or biochemical hyperandrogenism, and polycystic ovarian morphology on ultrasound, after exclusion of other etiologies. 1

Core Diagnostic Criteria

The Rotterdam criteria, established in 2003 and reaffirmed in the 2018 International Evidence-based Guideline, define PCOS when at least two of the following three features are present:

1. Oligo- or anovulation

   • Manifests as menstrual cycle anomalies
   • Includes amenorrhea, oligomenorrhea, or long cycles

2. Clinical and/or biochemical hyperandrogenism

   • Clinical signs: hirsutism, acne, male-pattern hair loss
   • Biochemical: elevated serum androgens

3. Polycystic ovarian morphology (PCOM) on ultrasound

   • Presence of at least 12 follicles in each ovary measuring 2-9 mm in diameter, and/or
   • Increased ovarian volume >10 ml 2

All other potential etiologies must be excluded before confirming a PCOS diagnosis 1, 3.

Ultrasonographic Assessment

Follicle number per whole ovary (FNPO) is the most accurate diagnostic marker for PCOM in adult women (sensitivity: 84%, specificity: 91%) 1. Alternative measures include:

• Ovarian volume (OV): Can be used when follicle counts cannot be accurately obtained
• Follicle number per single cross-section (FNPS): Another alternative when total follicle counts are not feasible

Important considerations for ultrasonography:

• Transvaginal ultrasound is preferred in adults for better accuracy
• Transabdominal/transrectal approaches may be used in adolescents
• Ultrasound is not recommended for PCOS diagnosis within 8 years of menarche due to overlap with normal multi-follicular appearance in adolescents 1

Special Populations

Adolescents

• Ultrasound criteria should not be used within 8 years of menarche 1
• Diagnosis requires both oligo-anovulation and hyperandrogenism
• Ovarian volume may be a more robust marker in adolescents, though evidence remains limited 1

Adults

• All three Rotterdam criteria can be applied
• FNPO is the gold standard for ultrasonographic diagnosis 1

Phenotypes of PCOS

Four recognized phenotypes exist based on the Rotterdam criteria 4:

1. Hyperandrogenism + oligo-anovulation + polycystic ovarian morphology
2. Hyperandrogenism + oligo-anovulation
3. Hyperandrogenism + polycystic ovarian morphology
4. Oligo-anovulation + polycystic ovarian morphology

Each phenotype has different long-term health and metabolic implications.

Exclusion of Other Disorders

Before confirming PCOS diagnosis, other conditions that may cause similar symptoms must be excluded:

• Thyroid dysfunction
• Hyperprolactinemia
• Non-classic congenital adrenal hyperplasia
• Androgen-secreting tumors
• Cushing's syndrome

Metabolic Screening

Patients diagnosed with PCOS should undergo metabolic screening:

• Weight, height, BMI calculation
• Waist circumference
• Blood pressure
• Laboratory parameters: plasma glucose, triglycerides, HDL cholesterol 2
• Oral glucose tolerance test (OGTT) is recommended for patients with BMI >30 kg/m² when fasting glucose is normal 2

Emerging Diagnostic Tools

Anti-Müllerian Hormone (AMH) has been proposed as a potential alternative to ultrasound for detecting PCOM. However, current evidence indicates several limitations:

• Lack of standardized assays
• Need for large international studies in well-defined populations
• Requirement for established cut-offs 1

AMH may eventually replace ultrasound in PCOS diagnosis once these issues are addressed, but it is not currently part of the official diagnostic criteria.

Common Pitfalls in PCOS Diagnosis

• Overreliance on ultrasound: Ultrasound findings alone are insufficient for diagnosis
• Ignoring age-specific considerations: Diagnostic approach differs between adolescents and adults
• Failure to exclude other disorders: Similar presentations can occur with other endocrine conditions
• Geographic variations: Diagnostic accuracy may vary by region due to differences in age, BMI, and diagnostic criteria 1
• Technology limitations: Ultrasound equipment advances have increased sensitivity, affecting established cut-offs 1

The diagnosis of PCOS remains challenging due to its heterogeneous presentation, but adherence to the Rotterdam criteria with appropriate consideration of age and exclusion of other disorders provides the most reliable diagnostic approach.