One of the most frequently performed tests among women to determine and confirm their pregnancy is the hCG hormone test. It is a blood or urine sample test which is usually recommended by the doctor to get a better understanding of the pregnancy. This blog gives a comprehensive overview of everything you should know about the hCG hormone test.

What is the hCG Test?

The hCG or human chorionic gonadotropin test confirms pregnancy by detecting the presence of hCG hormone in blood or urine. hCG starts being produced right after conception by the developing placenta, and its levels keep doubling every 72 hours in early pregnancy. Some amount of the hCG hormone is also excreted in the urine of pregnant women.

Purpose of hCG Test

The hCG test serves manifold objectives, including:

• Confirming pregnancy
• Ensuring pregnancy is advancing properly
• Detecting abnormalities like ectopic or molar pregnancies
• Diagnosing early miscarriage or pregnancy loss

When is a hCG test needed?

Here are some common situations warranting an hCG test:

• Missed or delayed periods
• Vaginal bleeding/spotting in early pregnancy
• Following up after fertility treatments like IVF
• Confirming pregnancy after a positive home test
• Pelvic pain possibly signalling ectopic pregnancy
• Suspected pregnancy with unusual symptoms

The hCG blood test can diagnose pregnancy even before missed periods if done through blood tests. Urine tests turn positive around the time of the expected period. Many clinicians recommend qualitative urine testing 1-2 weeks after missing periods for accuracy.

What Happens During the hCG Test?

Collection of Blood Sample

• The patient sits or lies down to ease vein access.
• A tourniquet is wrapped around the upper arm to make veins visible.
• The site is sterilised, often the elbow pit.
• 2-3 mL of blood is drawn using the needle from the vein into attached vials.
• The needle is withdrawn immediately, and the site is pressed to stop bleeding.

Collection of Urine Sample

• The patient is asked to collect midstream urine in a sterile container.
• A first-morning sample with highly concentrated urine is preferred.
• She should not have urinated for at least 4 hours prior.

Analysis of Sample

• The collected specimen then undergoes analysis for hCG hormone using immunoassays. 
• Many qualitative home urine pregnancy kits give quick results within 3-5 minutes. 
• Quantitative hCG blood tests require radio/chemiluminescent assays done in diagnostic laboratories to ascertain specific IU/L values.

Uses of hCG Test

• Confirming Pregnancy
  • By measuring the presence and levels of hCG, the test can conclusively diagnose pregnancy from the moment of conception practically. 
  • It can detect pregnancy before menstrual periods are missed or any symptoms appear.
• Tracking Pregnancy Progress
  • Serial quantitative hCG levels chart out embryo/foetal growth, comparing levels against reference ranges for corresponding pregnancy duration. 
  • Any abnormal rises or drops would necessitate further evaluation.
• Detecting Issues
  • Spurts, dips or slow increments in quantitative hCG levels can indicate complications.
  • Ectopic pregnancies demonstrate slower hCG rise, for example, while gestational trophoblastic disease sees abnormally rapid hCG increments. 
  • Miscarriage remains impending if hCG fails to double adequately.

hCG Test Procedure

The step-by-step process followed in collecting samples and performing the hCG test is outlined below:

• Pre-Test
  • Tell the doctor about any medications or supplements.
  • Discuss medical history, including last menstrual period, obstetric profile and symptoms.
• Sample Collection
  • The patient sits upright with arm extended, palms facing up.
  • A tourniquet wraps around the upper arm to render veins visible.
  • The site, usually cubital fossa, is sterilised with an alcohol-based sanitiser.
  • Using a sterile needle, 2-3 mL blood is drawn from the vein into attached vials.
  • Immediate pressure to stop the bleeding after withdrawal.
• Sample Analysis
  • The blood sample undergoes centrifugation to separate serum containing hCG hormone.
  • Serum quantitative hCG levels were measured through immunoassays.
  • Radioimmunoassay (RIA) and chemiluminescent immunoassay (CLIA) techniques enable accurate quantification.
  • Results are generally available within 48 hours.

How to Prepare For the hCG Test?

Basic preparations patients should undertake:

• For qualitative urine home kits, read directions properly to avoid errors.
• Collect early morning urine samples with the greatest hCG levels.
• Take only 1 test at a time; reusing it gives inaccurate results.
• Wait till 1-2 weeks after missing periods for hCG levels to rise sufficiently.
• For an ideal blood sample, drink adequate fluids & have something to eat prior.

What do hCG test results mean (if it is low and higher than normal levels)?

hCG Test Positive: Confirms pregnancy, but follow-up is imperative. Doctors may order serial quantitative hCG levels to monitor growth.

hCG Test Negative: Does not always rule out pregnancy; chances of false negative result exist due to myriad reasons like:

• Too early testing before hCG rises adequately
•  Sample errors leading to incorrect technique
•  Diluted urine lowers hCG concentration
•  Testing beyond the expiry date affects kit sensitivity
•  Defective kit

Reference hCG Ranges in Pregnancy

Weeks from Last Menstrual Period (LMP) Average Quantitative hCG Range (mIU/ml)

• 4 weeks LMP: 5-426 mIU/ml
• 5 weeks LMP: 18-7340 mIU/ml
• 6 weeks LMP: 1080-56,500 mIU/ml
• 9-12 weeks LMP: 25,700- 288,000 mIU/ml
• Second Trimester: 3,500-117,000 mIU/ml
• Third Trimester: 3,500-65,400 mIU/ml

Deviations from normal hCG ranges for corresponding gestational age indicate pathology. (1 mlU/L=1 IU/L)

What Abnormal Results Mean?

• Low hCG Levels
  • Indicate problems like ectopic pregnancies, possible miscarriage, wrong LMP dates or multiple reasons. 
  • Follow-up quantitative monitoring is needed.
• High hCG Levels
  • It can signify multiple pregnancies, molar pregnancy, or incorrect gestational age. 
  • Additional testing is mandatory for confirming the diagnosis.

Conclusion

There is no single definitive test; measuring hCG levels through blood and urine remains the foremost biochemical indicator of early pregnancy detection and monitoring foetal growth. Any aberrations in hCG concentrations typically signify underlying problems needing further diagnostic confirmation and appropriate medical management, thereby preventing complications. Tracking hCG levels in the first trimester thus provides invaluable insight into embryonic developmental milestones in utero and the well-being of the mother.

FAQs

1. What is a normal level of hCG test?

The average quantitative hCG hormone levels in blood tests during the first trimester are:

• 4 weeks gestation: 5-426 milliunits per millilitre (mIU/mL)
• 5 weeks: 18-7,340 mIU/mL
• 6 weeks: 1,080-56,500 mIU/mL

Levels peak between 8-11 weeks of pregnancy, declining subsequently.

2. What happens if the hCG test is positive?

Human chorionic gonadotropin starts being released from implantation itself, so blood tests for hCG can uncover pregnancy as early as 6-8 days after fertilisation of the egg before the first period is missed. Urine tests turn positive around the time of the expected period, generally when hCG is adequately concentrated.

3. What happens if the hCG test is negative?

In normal pregnancy, quantitative hCG levels roughly double every 48-72 hours. Too slow increments indicate chances of ectopic pregnancy, blighted ovum or impending miscarriage requiring emergency care. Too rapid rises can mean multiple pregnancies or molar pregnancies needing evaluation, too.

4. When can you detect hCG in pregnancy?

Yes, false negative pregnancy tests do sometimes occur if urine testing for qualitative hCG is done too early before optimal levels accumulate for detection. Using diluted urine, incorrect procedures, testing beyond expiry, or defective kits can also rarely give inaccurate negative results.