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

Diagnosing Polycystic Ovary Syndrome (PCOS)

PCOS is diagnosed when at least two of three criteria are present: oligo/anovulation, clinical or biochemical hyperandrogenism, and polycystic ovarian morphology on ultrasound, after excluding other causes of androgen excess. 1

Core Diagnostic Criteria (Rotterdam Criteria)

The diagnosis requires any two of the following three features 1, 2:

1. Oligo- or anovulation: Menstrual cycle length >35 days indicates chronic anovulation 1

2. Clinical or biochemical hyperandrogenism:

   • Clinical signs: acne, hirsutism, male-pattern balding, clitoromegaly 1
   • Biochemical: Elevated total testosterone (TT) or free testosterone (FT) as first-line laboratory tests 1

3. Polycystic ovarian morphology (PCOM): Detected on transvaginal ultrasound 1, 2

Ultrasound Diagnostic Thresholds

Follicle number per ovary (FNPO) ≥20 follicles is the gold standard ultrasonographic marker, with sensitivity of 87.64% and specificity of 93.74% 1, 3. This represents the most accurate diagnostic marker based on recent meta-analysis.

Alternative ultrasound markers when accurate follicle counting is not possible 3, 1:

• Ovarian volume (OV) >10 mL as the threshold for increased ovary size 1
• Follicle number per single cross-section (FNPS) 3

Technical specifications for optimal imaging 1:

• Use transvaginal ultrasound with ≥8 MHz transducer frequency in adults
• Do NOT use ultrasound as first-line investigation in adolescents (<17 years) due to poor specificity 1

Essential Clinical History and Physical Examination

Document the following specific elements 1:

• Onset and duration of androgen excess signs (rapid onset suggests androgen-secreting tumor) 1, 4
• Menstrual history: Cycle length, regularity, age at menarche 1
• Medication review: Exogenous androgens, hormonal contraceptives, spironolactone 1
• Lifestyle factors: Diet, exercise patterns, alcohol use, smoking 1
• Family history: Cardiovascular disease, diabetes 1
• Physical measurements: BMI and waist-hip ratio 1

Mandatory Differential Diagnosis Exclusions

Before confirming PCOS, you must rule out these conditions 1, 4:

High-priority exclusions (can mimic PCOS):

• Non-classic congenital adrenal hyperplasia (NCCAH): Check basal or ACTH-stimulated 17-hydroxyprogesterone 1, 4
• Cushing's syndrome: Look for buffalo hump, moon facies, hypertension, abdominal striae; screen with overnight dexamethasone suppression test or 24-hour urinary free cortisol 1, 4
• Androgen-secreting tumors (ovarian or adrenal): Suspect with rapid onset, severe hyperandrogenism, and very high serum androgen levels 1, 4
• Thyroid disease and hyperprolactinemia: Check TSH and prolactin levels 1, 4

Additional considerations 1:

• Acromegaly and genetic defects in insulin action
• Primary hypothalamic amenorrhea
• Primary ovarian failure

Laboratory Screening Tests

First-line hormonal assessment 5:

• Total testosterone
• Free testosterone
• DHEA-sulfate
• 17-hydroxyprogesterone (to exclude NCCAH)

Metabolic screening (especially in obese patients) 1, 5:

• Fasting glucose and insulin levels
• Lipid profile
• Screen all women with PCOS for type 2 diabetes and glucose intolerance 1

Emerging Diagnostic Markers

Anti-Müllerian Hormone (AMH) is being investigated as an alternative to ultrasound for PCOM detection, with significantly higher levels in PCOS patients 1, 6. However, AMH is not yet adequate for diagnosis due to lack of standardization across assays and absence of established cut-offs 1, 6.

Critical Diagnostic Pitfalls

Avoid these common errors:

• Do not diagnose PCOS in adolescents based on ultrasound alone – polycystic ovarian morphology is common in normal adolescents 1, 6
• Beware of medication effects: Spironolactone artificially lowers testosterone levels and improves menstrual regularity, masking diagnostic criteria 7. Ideally, conduct evaluation before initiating therapy or after a 2-4 week washout period 7
• Ensure proper ultrasound technique: Use transvaginal approach with high-frequency transducer (≥8 MHz) for accurate follicle counting 1
• Always exclude other causes of hyperandrogenism before confirming PCOS diagnosis – this is not optional 1, 4

Age-Specific Considerations

In adolescents (<20 years, at least 1 year post-menarche) 3:

• Avoid ultrasound as primary diagnostic tool due to high false-positive rate 1
• Rely more heavily on clinical and biochemical hyperandrogenism plus menstrual irregularity
• More data needed to support ultrasonographic criteria in this age group 3

In adults (18-50 years) 3:

• Full Rotterdam criteria apply
• Transvaginal ultrasound is appropriate and recommended 1