Sample stability:
-
5 days at 20-25 o C
-
14 days at 2-8 o C
-
12 months at -20 o C
A separate tube for hCG testing is strongly recommended. This will minimise delays in other biochemistry tests requested for the patient.
Units: IU/L
|
< 5 |
non pregnant (pre-menopausal) |
|
<14 |
postmenopausal |
|
5-25 |
equivocal, repeat in 48 hr |
|
>25 |
consistent with conception |
|
7-12 days after conception
|
first detectable level
|
| 4 - 6 weeks pregnancy: |
100 - 10,000 |
| 6 - 8 weeks pregnancy: |
5000 - 150,000 |
| 8 - 10 weeks pregnancy: |
25,000 - 200,000 (peak) |
| 2nd trimester: |
5,000 - 40,000 |
| 3rd trimester: |
3,000 - 30,000 |
Uncertainty of Measurement: 6%
Urgent service available 24 hours a day
Principle: Sandwich type immunoassay with chemiluminescence detection
Reagents: Roche HCG-BETA
Analyser: Cobas e801
CAUTION : Blood hCG tests may be subject to interference from heterophilic antibodies, which may cause false positives on rare ocassions. Before performing invasive procedures on the basis of this result alone, the result should be confirmed with a urine hCG test. If the hCG results do not concur with the clinical observations, contact the laboratory for help.
This test is suitable for diagnosing and monitoring pregnancy, ectopic pregnancy, and threatened abortion, and as a tumour marker for trophoblastic disease (hydatidiform mole or choriocarcinoma) or other tumours.
PREGNANCY
-
hCG level doubles every 2 days in early pregnancy.
-
hCG values > 200,000 are unusual in singleton pregnancies. Values higher than this occur in twin pregnancies, molar pregnancies, and trophoblastic tumours.
-
Ectopic pregnancies often have a lower than average hCG for dates and slower rate of increase.
-
The half life of hCG is 12 to 48 hours. Following birth or termination of pregnancy, serum hCG returns to undetectable values within a month, in most patients, although some take longer. Persistence of hCG should raise suspicion of retained products of conception.
TUMOUR MARKER
The hCG assay used at Labplus (Roche HCG Plus Beta) is able to measure all the variant forms of hCG found in association with tumours. When monitoring patients, the hCG test must always be performed by the same laboratory (different methods may give significantly different results).
The recommended monitoring protocol is as follows: weekly monitoring until 2 consecutive specimens show non-detectable levels, then monthly monitoring for up to 12 months. The monitoring interval may then be increased to 3 to 6 months over the next year.
POSTMENOPAUSAL hCG
: The normal pituitary secretes a low
level of hCG, which increases after menopause in women. hCG levels up to
28 IU/L have been seen in postmenopausal women in the absence of
neoplastic disease (ref 3). Pituitary hCG can be distinguished from
neoplastic production by giving subjects a high-estrogen oral
contraceptive pill for 3 weeks, which will suppress pituitary hCG.
END-STAGE RENAL DISEASE
: hCG may be elevated in end-stage renal disease (ref. 4). The level should remain fairly constant if the patient is not pregnant. A serum progesterone level may be helpful in ruling out pregnancy.
References:
1. Snyder et al. Diagnostic considerations in the measurement of hCG in aging women. Clin Chem 51: 1830-5, 2005
2. Wong LC, et al. Best Practice and Research: Clinical Obstetrics and Gynaecology 2003; 17(6): 893-903.
3. Cole LA. Reprod Biol Endocrinol 2009; 7:8
4. Fahy BG, Gouzd VA, Atallah JN. Pregnancy tests with end-stage renal disease. Journal of clinical anesthesia 2008;20(8):609-13.
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427