What labs are recommended for a patient suspected of having Polycystic Ovary Syndrome (PCOS)?

Recommended Laboratory Tests for Suspected PCOS

For patients suspected of having Polycystic Ovary Syndrome (PCOS), a comprehensive laboratory evaluation should include total testosterone, calculated free testosterone, and sex hormone-binding globulin (SHBG) as first-line tests, along with metabolic screening. 1

Hormonal Assessment

First-Line Tests

• Total Testosterone (TT) - Sensitivity 74%, Specificity 86% 1
• Calculated Free Testosterone (cFT) - Sensitivity 89%, Specificity 83% 1
• Free Androgen Index (FAI) - Sensitivity 78%, Specificity 85% 1
• Sex Hormone-Binding Globulin (SHBG) - Important for calculating FAI and interpreting testosterone levels

Additional Androgen Tests

• Androstenedione (A4) - Sensitivity 75%, Specificity 71% 1
• Dehydroepiandrosterone sulfate (DHEAS) - Sensitivity 75%, Specificity 67% 1

Other Reproductive Hormones

• Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH)
  • LH/FSH ratio >2 suggests PCOS in approximately 55% of patients 2
  • Recent data shows LH/FSH ratio <1 in about 82% of FHA patients 3

Tests to Rule Out Other Conditions

• Thyroid-Stimulating Hormone (TSH) - To exclude thyroid dysfunction 1
• Prolactin - To exclude hyperprolactinemia 1
• 17-hydroxyprogesterone - To exclude congenital adrenal hyperplasia 1
• Overnight dexamethasone suppression test or 24-hour urinary free cortisol - To exclude Cushing's syndrome when clinically suspected 1

Metabolic Assessment

• Fasting lipid profile (total cholesterol, LDL, HDL, triglycerides) 1, 4
• 2-hour 75g oral glucose tolerance test - Particularly important for women with BMI >25 kg/m² or with other risk factors for glucose intolerance 4
• Fasting glucose/insulin ratio - Ratio >4 suggests normal insulin sensitivity; lower values suggest insulin resistance 1
• Complete metabolic panel - To assess liver function 1

Imaging

• 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

Laboratory Test Considerations

Assay Methods

• Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is preferred for testosterone measurement with sensitivity of 71% and specificity of 92% 3
• Direct immunoassays are less accurate for female testosterone measurements 5

Timing of Tests

• Hormonal tests are ideally performed during early follicular phase (days 3-5) of menstrual cycle
• For women with amenorrhea, tests can be performed at any time

Clinical Correlation

• Laboratory results should be interpreted in conjunction with clinical features:
  • Menstrual irregularity (oligomenorrhea, amenorrhea)
  • Clinical hyperandrogenism (hirsutism, acne, alopecia)
  • Body mass index (BMI) and waist-hip ratio 1

Common Pitfalls to Avoid

• Relying solely on total testosterone without measuring free testosterone or SHBG
• Using inaccurate immunoassays for testosterone measurement in women
• Failing to exclude other causes of hyperandrogenism
• Not assessing metabolic parameters, which are commonly abnormal in PCOS
• Misdiagnosing functional hypothalamic amenorrhea with polycystic ovarian morphology (FHA-PCOM) as PCOS phenotype D 3

By following this comprehensive laboratory evaluation, clinicians can accurately diagnose PCOS and distinguish it from other conditions with similar presentations, while also assessing for associated metabolic abnormalities that require monitoring and management.