The glycoprotein hormones human chorionic gonadotropin (hCG), LH, FSH, and TSH are composed of two different subunits. The α subunit is similar in all of the glycoprotein hormones, and the β subunit is unique to each hormone. Highly specific assays allow hCG to be measured in the presence of other glycoprotein hormones. The increased sensitivity of the β-hCG test detects pregnancy as early as 6–10 days after implantation of the oocyte. A variety of poorly differentiated or undifferentiated neoplasms may produce ectopic chorionic gonadotropin. Assay for total hCG, both α and β subunits, or β-hCG may detect ectopic tumors (e.g., choriocarcinoma, hydatidiform mole, germinal testicular tumors). In these neoplasms, hCG is usually the product of syncytiotrophoblastic cells.

This qualitative test detects normal pregnancy. It is quicker but less sensitive (sensitivity, 20–50 mIU/mL) than the quantitative test. This test can be expected to become positive within 3 days of implantation (i.e., just after the first missed menstrual period). Cross-reactivity with LH is low, and false-positive results are rare. Occasionally, a patient with very high LH levels will give a borderline reaction. The qualitative test is usually done using urine.

The quantitative β-hCG test is used for nonroutine detection of hCG. It is sensitive to 1–3 mIU/mL. This test provides the most sensitive and specific test for the detection of early pregnancy, estimation of gestational age, and diagnosis of ectopic pregnancy or threatened spontaneous abortion. This test is also useful in the workup and management of testicular tumors. High levels may be found in choriocarcinoma, embryonal cell carcinoma, and ectopic pregnancy. hCG levels are extremely useful in following germ cell neoplasms that produce hCG, especially trophoblastic neoplasms. There is little cross-reactivity with LH.

Qualitative (for routine pregnancy tests): urine or serum negative (not pregnant)

Quantitative (for nonroutine detection of hCG):

• Men: <5.0 IU/L or mIU/mL

• Nonpregnant women: <5.0 IU/L or mIU/mL

• Pregnant women:

  • 1 week of gestation: 5–50 mIU/mL or IU/L

  • 2 weeks of gestation: 50–500 mIU/mL or IU/L

  • 3 weeks of gestation: 100–10,000 mIU/mL or IU/L

  • 4 weeks of gestation: 1080–30,000 mIU/mL or IU/L

  • 6–8 weeks of gestation: 3500–115,000 mIU/mL or IU/L

  • 12 weeks of gestation: 12,000–270,000 mIU/mL or IU/L

  • 13–16 weeks of gestation: up to 200,000 mIU/mL or IU/L

  • 17–40 weeks of gestation: gradual fall to 4000 mIU/mL or IU/L

1. Obtain a 5-mL venous blood sample. Serum is used for the test.

2. Observe standard precautions. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag.

3. Urine may be used for the qualitative test. First morning specimen is recommended.

1. Increased hCG values occur in the following conditions:

   1. Pregnancy

   2. Successful therapeutic insemination and in vitro fertilization

   3. Hydatidiform mole

   4. Choriocarcinoma

   5. Seminoma

   6. Ovarian and testicular teratomas

   7. Ectopic pregnancy

   8. Certain neoplasms of the lung, stomach, and pancreas

   9. Down syndrome (trisomy 21), midtrimester elevation

2. Decreased hCG values occur in:

   1. Threatened spontaneous abortion

   2. Ectopic pregnancy

   3. Trisomy 18, decrease at midtrimester

Pretest Patient Care

1. Explain test purpose and procedure.

2. Determine and record date of last menstrual period in women.

3. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

1. Lipemia, hemolysis, and radioisotopes administered within 1 week of testing may affect results.

2. Test results can be positive up to 1 week after complete abortion.

3. False-negative and false-positive results can be caused by many drugs (see Appendix E).

4. Heterophilic antibodies may falsely increase or decrease results.