Beta HCG quantitation

Keywords: BHCG titre, Human chorionic gonadotropin quantitative, QHCG, Beta human chorionic gonadotropin, Pregnancy test, hCG, Human chorionic gonadotropin (beta subunit), Chorionic gonadotropin

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 is also suitable for pregnancy-related applications. However, it should be noted that most commercial assays are not licensed for malignancy, as malignancy may produce variant hCG species.

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: 225-262.