From the Guidelines
A patient is considered pregnant when the serum hCG value is greater than 5 mIU/mL.
Detectable Level of hCG
- The detectable level of Human Chorionic Gonadotropin (hCG) in a serum test is greater than 5 mIU/mL 1.
- It is essential to note that values of 5 mIU/mL or less may occur in healthy nonpregnant patients 1.
- Elevated hCG levels may be unrelated to pregnancy, such as with pituitary dysfunction or neoplasia 1.
- The discriminatory level of hCG, at which a gestational sac should always be seen on transvaginal US in a normal singleton IUP, has historically been suggested as 1,000 to 2,000 mIU/mL 1.
- However, even a level of 2,000 mIU/mL has been found to be too low to exclude a normal IUP 1.
- If there is no transvaginal US evidence of a gestational sac when a single serum hCG is 3,000 mIU/mL or higher, it is unlikely there will be a viable IUP 1.
From the Research
Detectable Level of Human Chorionic Gonadotropin (hCG) in Serum Test
- The detectable level of hCG in a serum test can vary depending on the assay used and the individual's pregnancy status.
- According to 2, hCG is nearly always detectable in serum and urine within 16 days after ovulation.
- A study published in 3 found that hCG levels can be detected as early as six days after presumed conception and peak between 56 and 68 days.
- The cutoff values of serum β-HCG levels for predicting biochemical pregnancy were found to be 213.15 IU/L, 986.65 IU/L, and 2206.5 IU/L for singletons, multiples, and twins or triplets, respectively, as reported in 4.
- False-positive serum hCG results can occur, with levels generally <1000 mIU/mL, as noted in 5.
- The detection of hCG can be achieved through various advanced technologies, including electrochemical immunoassay, chemiluminescent immunoassay, and fluorescence immunoassay, as reviewed in 6.
Factors Affecting hCG Detection
- The analytical specificity and sensitivity of hCG assays can vary, leading to differences in detectable levels 2.
- Interference by non-hCG substances and the detection of pituitary hCG can cause false-positive results 5.
- The use of alternative types of hCG assays can help recognize false-positive results 5.