What laboratory tests should be ordered for the diagnosis and management of Polycystic Ovary Syndrome (PCOS)?

Laboratory Tests for Diagnosis and Management of PCOS

The essential laboratory tests for diagnosing and managing Polycystic Ovary Syndrome (PCOS) include total testosterone, free testosterone calculation, TSH, prolactin, 17-hydroxyprogesterone, fasting glucose/insulin ratio, and a 2-hour 75g oral glucose tolerance test with lipid profile. 1

Diagnostic Laboratory Tests

Hormonal Assessment for PCOS Diagnosis

• Total testosterone (TT): Should be measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for superior specificity (92%) with sensitivity of 74% and specificity of 86% 1
• Free testosterone (FT): Should be calculated rather than directly measured (sensitivity 89%, specificity 83%) 1
• Free Androgen Index (FAI): Sensitivity 78%, specificity 85% 1
• Androstenedione (A4): Sensitivity 75%, specificity 71% 1
• Dehydroepiandrosterone sulfate (DHEAS): Sensitivity 75%, specificity 67% 1

Tests to Exclude Other Causes of Hyperandrogenism

• Thyroid-stimulating hormone (TSH) to rule out thyroid dysfunction 1
• Prolactin levels to exclude hyperprolactinemia 1
• 17-hydroxyprogesterone to rule out congenital adrenal hyperplasia 1
• Overnight dexamethasone suppression test or 24-hour urinary free cortisol test to exclude Cushing's syndrome 1

Metabolic Evaluation

Insulin Resistance and Glucose Metabolism

• Fasting glucose/insulin ratio: A ratio >4 suggests normal insulin sensitivity; lower values indicate insulin resistance 1
• 2-hour 75g oral glucose tolerance test: Particularly important for women with BMI >25 kg/m² or other risk factors for glucose intolerance 1

Lipid Profile

• Complete fasting lipid profile: Total cholesterol, LDL, HDL, and triglycerides 1

Imaging Evaluation

• Transvaginal ultrasound: 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
  • Also evaluates endometrial thickness and ovarian cyst complications 1

Clinical Pearls and Pitfalls

Common Diagnostic Pitfalls

• Misdiagnosing functional hypothalamic amenorrhea with polycystic ovarian morphology (FHA-PCOM) as PCOS phenotype D is a common error 1
• Relying solely on laboratory tests without considering clinical criteria: Remember that PCOS diagnosis requires at least two of three criteria (chronic anovulation, hyperandrogenism, polycystic ovaries) 1
• Using inappropriate testosterone assays: Immunoassays may lack specificity; LC-MS/MS is preferred 1

Important Considerations

• Laboratory evaluation should be interpreted in the context of clinical presentation, including menstrual irregularities, signs of hyperandrogenism, and ultrasound findings 1, 2
• The LH/FSH ratio may be elevated (>2:1 in 55% of patients, >3:1 in 26.2% of patients), but this is not included in the diagnostic criteria 3
• Regular metabolic screening is crucial due to the high risk of metabolic syndrome and type 2 diabetes in PCOS patients 1

Follow-up Laboratory Monitoring

• Annual metabolic screening: Fasting glucose, oral glucose tolerance test, and lipid profile 1
• Hormone levels: May be monitored to assess treatment response, particularly when using anti-androgen therapies 1
• Endometrial thickness: Should be monitored in patients with oligomenorrhea or amenorrhea 1

By following this comprehensive laboratory approach, clinicians can accurately diagnose PCOS, exclude other causes of hyperandrogenism, and monitor for metabolic complications that frequently accompany this syndrome.