hCG - plasma, serum or urine

Last updated: Thursday, 25, March, 2004

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Item Process
Specimen

5 mL blood in a plain or lithium heparin tube.

Random urine (early morning is best) may be acceptable for a qualitative test.

Method

Immunoassay - qualitative or quantitative.

Reference Interval

<5 mIU/L (non-pregnant).

The reference interval in pregnancy varies with gestational age.

Application

Qualitative test: diagnosis of pregnancy including ectopic pregnancy.

Quantitative test: diagnosis of threatened abortion or ectopic pregnancy (sequential tests may be needed).

Monitoring hCG-producing tumours (eg, hydatidiform mole, uterine choriocarcinoma, gonadal and extragonadal germ cell tumours): an assay that detects the free β subunit as well as the whole molecule is required and are also suitable for pregnancy-related applications.

Interpretation

If pregnancy occurs the test becomes positive 6-10 days following ovulation.

The normal doubling time for the hormone in early pregnancy is 36 hours. Low levels for gestational age and/or a low rate of increase may indicate threatened abortion or ectopic pregnancy.

High levels for gestational age may indicate molar pregnancy.

Increased levels in a patient with a history of an hCG-producing tumour indicate residual or recurrent tumour.

Reference

Duffy MJ. Crit Rev Clin Lab Sci 2001; 38(3): 225-262.