What laboratory tests are recommended for the diagnosis and management of Polycystic Ovary Syndrome (PCOS)?

Laboratory Tests for PCOS Diagnosis and Management

For the diagnosis and management of Polycystic Ovary Syndrome (PCOS), laboratory testing should include TSH, prolactin, 17-hydroxyprogesterone, total and free testosterone, fasting glucose/insulin, lipid profile, and a 2-hour oral glucose tolerance test. 1

Core Diagnostic Tests

The diagnosis of PCOS requires at least two of three criteria (Rotterdam criteria): chronic anovulation, hyperandrogenism, and polycystic ovaries. The following laboratory tests are essential to establish diagnosis:

Androgen Assessment

• Total testosterone and free testosterone - First-line tests for biochemical hyperandrogenism (Free testosterone sensitivity 89%, specificity 83%; Total testosterone sensitivity 74%, specificity 86%) 1
• Free Androgen Index (FAI) - Sensitivity 78%, specificity 85% 1
• Androstenedione - Sensitivity 75%, specificity 71% 1
• DHEAS (Dehydroepiandrosterone sulfate) - Sensitivity 75%, specificity 67% 1

Exclusion of Other Disorders

• TSH (Thyroid-stimulating hormone) - To rule out thyroid disorders 1
• Prolactin - To exclude hyperprolactinemia 1, 2
• 17-hydroxyprogesterone - To rule out congenital adrenal hyperplasia 1, 2
• Overnight dexamethasone suppression test or 24-hour urinary free cortisol - To exclude Cushing's syndrome when clinically suspected 1, 2

Metabolic Assessment

Given the strong association between PCOS and metabolic disorders, these tests are crucial:

• Fasting glucose and insulin - To assess insulin resistance; fasting glucose/insulin ratio >4 suggests reduced insulin sensitivity 1, 2
• 2-hour oral glucose tolerance test with 75g glucose load - For comprehensive evaluation of glucose metabolism 1
• Fasting lipid profile - Including total cholesterol, LDL, HDL, and triglycerides 1, 3

Imaging

While not a laboratory test, transvaginal ultrasound is an essential diagnostic tool:

• Should be performed between days 3-9 of the menstrual cycle 1
• Diagnostic threshold: ≥20 follicles (2-9mm) per ovary or ovarian volume ≥10ml 1, 4

Common Pitfalls to Avoid

1. Not excluding other disorders - Failure to rule out conditions that mimic PCOS can lead to misdiagnosis 2, 5
2. Incomplete androgen assessment - Relying on a single androgen test may miss biochemical hyperandrogenism 1
3. Overlooking metabolic screening - PCOS patients are at high risk for metabolic disorders, making comprehensive metabolic assessment crucial 1, 3
4. Inappropriate timing of ultrasound - Ultrasound performed outside days 3-9 of the menstrual cycle may affect follicle count accuracy 1

Special Considerations

• Adolescents: Diagnosis can be challenging; hyperandrogenism is central to presentation 5
• Postmenopausal women: No consistent phenotype; diagnosis is more difficult 5
• Obese patients: More extensive metabolic screening is recommended 2, 3

The laboratory evaluation for PCOS should be comprehensive but targeted, focusing on confirming the diagnosis while excluding other potential causes of the patient's symptoms, and assessing for metabolic complications that frequently accompany this syndrome.