Laboratory Services

Estriol, Unconjugated, Serum

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Updated Test Information:

Test Description
Estriol, Unconjugated, Serum

E3 (Estriol); Estriol; UE3 (Unconjugated Estriol); Unconjugated Estriol

Test ID
General Information

Useful for:

  • A part of second trimester or cross-trimester biochemical screening for Down syndrome and trisomy 18 syndrome

  • A marker of fetal demise

  • An adjunct biomarker in the prenatal diagnosis of disorders of fetal steroid metabolism, including Smith-Lemli-Opitz syndrome (SLO)(3-4), and X-linked ichthyosis (placental sulfatase deficiency disorders)

  • Evaluating primary or secondary fetal adrenal insufficiency after excluding other rare single gene defects, including aromatase deficiency, 17 alpha-hydroxylase deficiency and/or various forms of congenital adrenal hyperplasia

Specimen Type


Specimen Requirements

  • Preferred: Red Top

  • Acceptable: Serum Gel (SST)

Minimum Sample Volume

0.5 mL


  • Refrigerated (preferred): 14 days

  • Frozen: 90 days

Unacceptable Specimen Conditions

Gross hemolysis


  • Patients who have been exposed to animal antigens, either in the environment or as part of treatment or imaging procedures, may have circulating anti-animal antibodies present which may interfere with the assay reagents and produce unreliable results

  • If the clinical picture is inconsistent with the test results, clinicians should consider the possibility of a preanalytical or analytical error and contact the laboratory


Immunoenzymatic Assay

Estimated TAT

1-3 days

Testing Schedule



14 days

CPT Code(s)


Reference Range

Males: < 0.07 ng/mL
Females: < 0.08 ng/mL

Performing Lab


LOINC Code(s)


Additional Information