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Test Directory -  Pregnancy test

Synonyms

Urine (or serum) human Chorionic Gonadotrophin (hCG)

Clinical Indications

During pregnancy, the concentration of hCG in urine rises rapidly and may be detected by some home pregnancy tests about 3 days after implantation. The rise in hCG varies considerably from one woman to another and therefore a clear relationship between hCG level and progress of pregnancy cannot be given. As a rough guide a level of 50 IU/L is reached about the day of the first missed period and a level of 200 IU/L about 4 days later. Early pregnancy loss (EPL) or pregnancies that fail to properly implant may also produce hCG and patients may get a positive pregnancy test result in the last week of their menstrual cycle (26-29 days after start of last menstrual period). EPL is common and a cause of 'false-hopes' pregnancy. Most women will be unaware they have had an EPL and normal (or slightly heavier than normal) menses will follow.

Home Pregnancy Tests

Home pregnancy tests are marketed towards the earliest possible detection of pregnancy, and may give positive results in non-viable pregnancies. The laboratory uses a test with a detection limit of 25 IU/L to confirm pregnancy. There will be situations where a home pregnancy test is positive and a laboratory test is negative. If the sample was taken too early (see timing of sample) we suggest a repeat at the recommended time. For exclusion of pregnancy or investigation of problem pregnancies a serum hCG is a more reliable indicator

Request Form 

Microbiology form (Green)

Availability

On request during normal working hours

Specific Criteria

Confirmation of suspected pregnancy
Please state date of last missed period (LMP)

Turnaround Time

Same day (Monday to Friday)
Urgent reports will be telephoned on request

Timing of Sample

To avoid positive results due to EPL, samples should be taken at least 32 days since start of last period (or 4 days after missing a period). This will assure detection of a potentially viable pregnancy

Specimen

Early morning urine

Volume

Minimum 5 ml

Container

Plain (white top) universal only
Samples collected into the patient's own container or boric acid bottle (red cap universal) will be rejected

Lab. Handling

Samples should be tested on the day of receipt

Causes for Rejection

Incorrectly and/or Insufficiently labelled sample
Unsuitable sample container (see above)

Samples can not be tested if  >48hours old upon reaching the laboratory

Interpretation

Negative results do not exclude early (less than 18 days after conception) pregnancy, which may be detected by some 'home pregnancy tests'
Positive results are consistent with pregnancy, but should be confirmed by clinical assessment

Test may remain positive for up to 2 weeks following childbirth and up to 4 weeks following abortion
. Neoplastic disorders such as hydatidiform mole and choriocarcinoma may produce high levels of urinary hCG

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Version 1.1 / February 2014

Last edited 16/04/14