Diagnosis of 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 are the most widely accepted diagnostic framework for PCOS, requiring the presence of at least two of the following three criteria:
Chronic anovulation/oligo-ovulation - manifested as:
- Menstrual irregularity (cycle length >35 days)
- Fewer than 8 menstrual cycles per year
- Absence of menstruation for >3 months
Hyperandrogenism
- Clinical signs: Hirsutism, acne, male-pattern alopecia
- Biochemical markers: Elevated androgens in laboratory testing
Polycystic ovaries on ultrasound
- ≥20 follicles (2-9mm) per ovary OR
- Ovarian volume ≥10ml 1
Laboratory Evaluation
First-Line Tests for Biochemical Hyperandrogenism
- Total testosterone (TT) - sensitivity 74%, specificity 86% 1
- Free testosterone (FT) - sensitivity 89%, specificity 83% 1
- Ideally measured by mass spectrometry or equilibrium dialysis
- Free Androgen Index (FAI) - sensitivity 78%, specificity 85% 1
- Good alternative when mass spectrometry is unavailable
Additional Androgen Tests
- Androstenedione (A4) - sensitivity 75%, specificity 71% 1
- Dehydroepiandrosterone sulfate (DHEAS) - sensitivity 75%, specificity 67% 1
- Calculated bioavailable testosterone - sensitivity 76%, specificity 83% 1
Exclusion of Other Disorders
- Thyroid-stimulating hormone (TSH) - to rule out thyroid disorders
- Prolactin - to exclude hyperprolactinemia
- 17-hydroxyprogesterone - to rule out congenital adrenal hyperplasia
- Overnight dexamethasone suppression test or 24-hour urinary free cortisol - to exclude Cushing's syndrome 1
Metabolic Assessment
- Fasting lipid profile
- Fasting glucose/insulin ratio
- 2-hour 75g oral glucose tolerance test (OGTT) - especially for patients with BMI >25 kg/m² 1
Ultrasound Evaluation
- Diagnostic threshold: ≥20 follicles (2-9mm) per ovary OR ovarian volume ≥10ml 1
- Timing: Best performed in early follicular phase in menstruating women
- Important note: Ultrasound findings alone are insufficient for diagnosis and must be correlated with clinical and biochemical findings 1
- Adolescents: Ultrasound is not recommended as first-line investigation in women <17 years due to high prevalence of multicystic ovaries in this age group 2
Special Considerations
Adolescents
- Diagnosis is challenging due to overlap with normal pubertal changes
- Persistent oligomenorrhea 2-3 years post-menarche suggests PCOS
- Focus on clinical hyperandrogenism and menstrual irregularities rather than ultrasound 2
Diagnostic Pitfalls to Avoid
- Relying solely on ultrasound - PCOS is a clinical diagnosis requiring correlation with symptoms and biochemical findings
- Using inappropriate testosterone assays - Direct immunoassays have lower accuracy; mass spectrometry is preferred 3
- Failing to exclude other disorders - Several conditions can mimic PCOS
- Not considering phenotypic variations - Different PCOS phenotypes have varying clinical presentations and long-term risks 4
Diagnostic Algorithm
- Assess menstrual pattern - Document cycle length, regularity, and amenorrhea
- Evaluate for clinical hyperandrogenism - Hirsutism, acne, alopecia
- Order appropriate laboratory tests - TT, FT or FAI as first line; exclusionary tests as needed
- Consider ultrasound - If diagnosis remains unclear after clinical and laboratory assessment
- Exclude other disorders - Thyroid disease, hyperprolactinemia, Cushing's syndrome, congenital adrenal hyperplasia
- Apply Rotterdam criteria - Confirm presence of at least two of three criteria
- Document PCOS phenotype - For appropriate management and risk assessment
By following this systematic approach, clinicians can accurately diagnose PCOS and develop appropriate management strategies for affected women.