What biochemical findings confirm a diagnosis of polycystic ovarian syndrome (PCOS) in a patient with polycystic ovaries on ultrasound?

Biochemical Findings Confirming PCOS Diagnosis

The correct answer is D: High Free Androgen Index, High free testosterone—these are the key biochemical markers that confirm PCOS diagnosis in a patient with polycystic ovaries on ultrasound and clinical features of the syndrome. 1

Diagnostic Framework

PCOS diagnosis requires at least 2 of 3 Rotterdam criteria: hyperandrogenism (clinical or biochemical), ovulatory dysfunction, and polycystic ovary morphology on ultrasound. 1, 2 Since this patient already has polycystic ovaries on ultrasound and suspected clinical features, biochemical confirmation of hyperandrogenism completes the diagnosis. 1

First-Line Biochemical Tests for PCOS

The diagnostic workup should prioritize:

• Total testosterone has 74% sensitivity and 86% specificity for PCOS diagnosis 1
• Free testosterone (calculated or measured by equilibrium dialysis) has the highest sensitivity at 89% with 83% specificity 1, 2
• Free Androgen Index (FAI) has 78% sensitivity and 85% specificity for PCOS diagnosis 1, 2

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the preferred measurement method due to superior accuracy compared to direct immunoassays, which have lower sensitivity and specificity. 1, 2

Why Other Options Are Incorrect

Option A (Normal range LH, FSH, and free testosterone)

• Normal androgens would not confirm PCOS diagnosis 1
• While LH/FSH ratio >2 may suggest PCOS, this is a second-line test and normal values don't exclude the diagnosis 3

Option B (High 17-hydroxyprogesterone)

• Elevated 17-hydroxyprogesterone suggests non-classic congenital adrenal hyperplasia, which is a differential diagnosis that must be excluded, not a confirmatory finding for PCOS 2, 3

Option C (Testosterone very high, FSH and LH normal)

• Very high testosterone (particularly rapid onset with severe hyperandrogenism) raises concern for androgen-secreting tumors of the ovary or adrenal gland, requiring urgent evaluation 2, 3
• This pattern warrants exclusion of malignancy rather than confirming PCOS 2

Option E (High CA125 and CEA)

• These are tumor markers with no role in PCOS diagnosis 1, 2

Critical Considerations for This 17-Year-Old Patient

Ultrasound should not be used as a primary diagnostic criterion in adolescents <8 years post-menarche due to high false-positive rates from normal multi-follicular ovaries in this age group. 4, 2 However, if polycystic ovaries are already documented and clinical features are present, biochemical hyperandrogenism (elevated free testosterone and FAI) provides the necessary confirmation. 1, 2

Additional Differential Diagnosis Testing

While confirming PCOS, also measure:

• Prolactin to exclude hyperprolactinemia 2, 3
• TSH to rule out thyroid disease 2, 3
• 17-hydroxyprogesterone to exclude non-classic congenital adrenal hyperplasia 2, 3
• Fasting glucose and lipid panel for metabolic screening, as all women with PCOS should be screened for type 2 diabetes and dyslipidemia 2