How to Diagnose PCOS: Clinical Workup and Criteria

Polycystic ovary syndrome (PCOS) affects approximately 10% of women of reproductive age, making it one of the most common endocrine disorders encountered in gynecology practice. Early and accurate diagnosis is crucial for managing symptoms, preventing long-term complications, and addressing fertility concerns.

The diagnostic approach to suspected PCOS has evolved with the 2023 International evidence-based guideline and NICE 2026 updates, which refine the classic Rotterdam criteria with practical clinical pathways.

Understanding PCOS and Its Diagnostic Criteria

PCOS is a heterogeneous condition characterized by a combination of reproductive, metabolic, and endocrine abnormalities. The diagnosis rests on recognizing patterns rather than a single definitive test.

The Rotterdam Criteria (Revised 2023)

The internationally accepted Rotterdam criteria require two out of three of the following, after excluding other conditions that can mimic PCOS:

• Clinical and or biochemical hyperandrogenism: Hirsutism, acne, male-pattern hair loss, or elevated total/free testosterone or raised Free Androgen Index (FAI)
• Ovulatory dysfunction: Infrequent or absent ovulation, typically manifesting as irregular or absent menstrual cycles (oligomenorrhea or amenorrhea)
• Polycystic ovarian morphology on ultrasound: Defined as 12 or more follicles measuring 2-9 mm in diameter in one or both ovaries, and or increased ovarian volume greater than 10 cm3

Critical note: Polycystic ovaries do not have to be present to make the diagnosis, and the finding of polycystic ovaries alone does not establish the diagnosis. Approximately 20-30% of women without PCOS have polycystic-appearing ovaries on ultrasound.

Adolescent Diagnosis: Stricter Criteria

In adolescents (under 18 years), diagnosing PCOS is more challenging because many features of PCOS overlap with normal pubertal physiology. The 2023 International guideline and NICE 2026 recommend:

• Both hyperandrogenism AND irregular menstrual cycles are required
• Do not diagnose PCOS until more than 2 years after menarche
• Ultrasound is less helpful in adolescents due to the high prevalence of multi-follicular ovaries as a normal pubertal finding
• Girls under 18 with suspected PCOS should be considered at increased risk and reassessed at or before age 18

Step-by-Step Diagnostic Workup

1. Detailed Clinical History

Begin with a comprehensive history focusing on key diagnostic features:

Menstrual history:

• Age at menarche
• Cycle regularity and length
• Presence of oligomenorrhea (cycles >35 days) or amenorrhea
• Duration and heaviness of bleeding

Androgen excess symptoms:

• Hirsutism (excessive hair growth in male pattern)
• Acne, particularly if persistent or severe
• Male-pattern hair loss (androgenetic alopecia)
• Rapid virilization (deepening voice, clitoromegaly, severe hirsutism) — red flag requiring urgent evaluation

Metabolic and reproductive concerns:

• Weight history and BMI
• Difficulty losing weight
• Infertility or subfertility
• Family history of PCOS, diabetes, or cardiovascular disease
• Symptoms of insulin resistance (acanthosis nigricans)

Exclusion of other conditions:

• Symptoms of thyroid dysfunction (fatigue, weight changes, hair loss)
• Galactorrhea (suggestive of hyperprolactinemia)
• Easy bruising or excessive bleeding (coagulopathy)
• Rapid onset of severe symptoms (suggestive of androgen-secreting tumor)

2. Physical Examination

General examination:

• BMI calculation (obesity is present in 60-80% of women with PCOS)
• Blood pressure measurement
• Signs of insulin resistance: acanthosis nigricans (velvety, dark patches on neck, axillae)
• Signs of virilization: deepening voice, clitoromegaly, increased muscle bulk, reduced breast size

Dermatological examination:

• Ferriman-Gallwey score for hirsutism assessment
• Presence and severity of acne
• Pattern of hair loss

Pelvic examination:

• Not routinely required for diagnosis
• May reveal signs of androgen excess or other gynecological conditions

3. Laboratory Investigation

First-line hormone tests (day 1-5 of cycle if menstruating):

Metabolic screening:

Additional tests based on clinical presentation:

• 17-hydroxyprogesterone: If congenital adrenal hyperplasia (CAH) is suspected (especially with rapid virilization)
• DHEAS: If androgen-secreting adrenal tumor is suspected
• Cortisol tests: If Cushing syndrome is suspected
• Von Willebrand panel: If bleeding disorder is suspected

4. Pelvic Ultrasound

Indications for ultrasound in adults:

• When clinical and biochemical criteria are not both met
• To assess for polycystic ovarian morphology
• When other pelvic pathology is suspected

Ultrasound criteria for PCOS (adults only):

• 12 or more follicles measuring 2-9 mm in diameter in one or both ovaries
• Increased ovarian volume >10 cm3
• Note: Ultrasound is not required if both clinical hyperandrogenism and ovulatory dysfunction are present

Important limitations:

• Ultrasound should NOT be used for diagnosing PCOS in adolescents
• Transvaginal ultrasound is preferred in sexually active adults
• Transabdominal ultrasound may be used in adolescents or non-sexually active patients

5. When to Refer to Endocrinology

Refer patients with suspected PCOS to endocrinology when:

• Severe symptoms: Signs of virilization (rapid onset of deepening voice, clitoromegaly, severe hirsutism)
• Markedly elevated testosterone: >5 nmol/L or >2x upper limit of normal
• Abnormal DHEAS, androstenedione, or 17-hydroxyprogesterone levels (suggestive of CAH or androgen-secreting tumor)
• Diagnostic uncertainty after initial evaluation
• Complex metabolic complications requiring specialized management
• Persistent hyperprolactinemia requiring further investigation

Red Flags

Seek urgent evaluation or referral when any of the following are present:

• Rapid virilization: Rapid onset of deepening voice, clitoromegaly, severe hirsutism, reduced breast size, increased muscle bulk
• Testosterone >5 nmol/L or >2x upper limit of normal: Suggestive of androgen-secreting tumor
• Very high 17-hydroxyprogesterone: Suggestive of congenital adrenal hyperplasia
• Signs of Cushing syndrome: Central obesity, moon face, striae, proximal muscle weakness
• Severe uncontrolled hypertension or other cardiovascular risk factors
• Suspected malignancy: Rapidly enlarging pelvic mass

Common Questions

What are the differences between adult and adolescent PCOS diagnosis?

In adults, PCOS can be diagnosed with 2 of 3 Rotterdam criteria. In adolescents under 18, both hyperandrogenism AND irregular menstrual cycles are required due to the overlap with normal pubertal development. Ultrasound is not recommended for adolescent diagnosis because multi-follicular ovaries are common in normal puberty.

When is ultrasound not needed for PCOS diagnosis?

Ultrasound is not required when both clinical/biochemical hyperandrogenism AND ovulatory dysfunction (irregular cycles) are clearly present. The diagnosis can be made on clinical and biochemical grounds alone in these cases.

How do I interpret testosterone levels in PCOS?

Testosterone levels in PCOS are typically normal to mildly elevated. Markedly elevated testosterone (>5 nmol/L or >2x ULN) suggests an androgen-secreting tumor rather than PCOS. Testosterone production roughly doubles in the early follicular phase, so testing on day 1-5 of the cycle provides the most accurate baseline.

What conditions should be excluded before diagnosing PCOS?

Always exclude: thyroid dysfunction (hypo/hyperthyroidism), hyperprolactinemia, congenital adrenal hyperplasia (CAH), Cushing syndrome, androgen-secreting tumors, and premature ovarian failure. These conditions can present with similar symptoms of irregular cycles and androgen excess.

Protocol Summary

• Obtain detailed menstrual history including cycle regularity, androgen excess symptoms, and metabolic concerns
• Perform physical examination focusing on BMI, blood pressure, signs of insulin resistance, and virilization
• Order first-line hormone tests: testosterone, SHBG, LH, FSH, prolactin, TSH on cycle day 1-5 if menstruating
• Calculate Free Androgen Index (FAI) from testosterone and SHBG results
• Perform metabolic screening: fasting glucose or HbA1c, fasting lipid profile
• Order pelvic ultrasound only if clinical and biochemical criteria are not both met (not for adolescents)
• Exclude other conditions: thyroid dysfunction, hyperprolactinemia, CAH, Cushing syndrome, androgen-secreting tumors
• Refer to endocrinology for severe symptoms, markedly elevated testosterone, or diagnostic uncertainty

How Rovetia Helps

Rovetia streamlines PCOS evaluation by enabling structured documentation of menstrual history, androgen excess symptoms, and metabolic risk factors directly in the patient's clinical record. The AI-powered system extracts key findings from clinician notes and patient-reported data, automatically flagging patients who meet criteria for specialist referral or additional metabolic screening. This helps gynecologists ensure comprehensive evaluation while maintaining efficient workflow.

Sources

• NICE guideline on PMOS
• COMMUNITY GYNAECOLOGY GUIDELINES - Polycystic Ovary Syndrome Pathway
• PCOS / PMOS - Remedy BNSSG ICB

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