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βhCG
Principle
Detection of hCG in urine or blood within 3–4 weeks of the last menstrual period is the most reliable indicator for confirming pregnancy. hCG is initially secreted by the trophoblast, and later by the chorion and placenta. Levels rise exponentially, peaking during the first trimester, and decline to a plateau during the second and third trimesters. Measurement of hCG is also useful in diagnosing ectopic pregnancy, threatened abortion, and multiple gestation.
Specimen Requirements
Specimen
Serum (serum separator tube, SST)
Collection
Allow clotting for 30 minutes; centrifuge 10 minutes at ~1000 g; transfer serum to a separate plastic vial. Ensure no red blood cells are present.
Processing
Allow clotting for 30 minutes; centrifuge 10 minutes at ~1000 g; transfer serum to a separate plastic vial. Ensure no red blood cells are present.
Storage and Transport
≤ –20 °C; avoid repeated freeze–thaw cycles
Unacceptable Specimens
Unspun or hemolyzed specimens (may yield falsely elevated results)
Method
Enhanced chemiluminescence.
Normal Range
Approximate Gestational Age Approximate hCG Range (mIU/mL)
| 0–1 week | 0–50 |
| 1–2 weeks | 40–300 |
| 2–3 weeks | 100–1,000 |
| 3–4 weeks | 500–6,000 |
| 1–2 months | 5,000–200,000 |
| 2–3 months | 10,000–100,000 |
| 2nd trimester | 3,000–50,000 |
| 3rd trimester | 1,000–50,000 |
| Males & non-pregnant females | < 5.0 |
| Postmenopausal females | 0.1–11.6 |
Turnaround Time
24 hours
References
- Saxena B, Landesman R. Diagnosis and Management of Pregnancy by the Receptor Assay of Human Chorionic Gonadotropin. Am J Obstet Gynecol. 131:97–107; 1978.
- Hertz JB et al. Progesterone and Human Chorionic Gonadotropin in Serum and Pregnandiol in Urine in Treated Abortion. Acta Obstet Gynecol Scand. 59:23–27; 1980.
- Braunstein GD et al. First-trimester Chorionic Gonadotropin Measurements as an Aid in the Diagnosis of Early Pregnancy Disorders. Am J Obstet Gynecol. 13:25–32; 1978.
- Check JH et al. Analysis of Serum Human Chorionic Gonadotropin Levels in Normal Singleton, Multiple, and Abnormal Pregnancies. Human Reproduction. 7:1176–1180; 1992.