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Human Chorionic Gonadotropin for Pregnancy, serum, ≥ 18 year old (Adult)
|Available Stat?||Yes, for ectopic R/O only|
|Performed by||Parnassus & Mt. Zion Chemistry|
|In House Availability||
|Method||Parnassus: Beckman Access Chemiluminescent Immunoassay on DxI600 platform.
Mt. Zion: Access 2 Immunoassay
|Collection Instructions||Be sure that you are selecting the appropriate test for pediatric vs. adult patients. Two tests are offered so that the results can be appropriately filtered to appear in MyChart.|
|Container type||Gold top|
|Amount to Collect||1 mL blood|
|Preferred volume||0.5 mL serum|
|Min. Volume||0.3 mL serum|
HCG ranges for normal pregnancy quoted by the manufacturer of the assay from the literature are:
|Synonyms||HCG; Beta-HCG; b-HCG; gonadotropin tests; choriogonadotropin; UCG; pregnancy test; ectopic pregancy test|
|Stability||Room temperature 8 hours, refrigerated 2 days, frozen at -20C 6 months|
|Turn around times||STAT 1 hour, Routine same or next day.|
|Additional information||Be sure that you are selecting the appropriate test for pediatric vs. adult patients. Two tests are offered so that the results can be appropriately filtered to appear in MyChart.
1. Detects intact hCG, nicked hCG, free beta hCG subunits, hyperglycosylated hCG, and possibly pituitary hCG (1). Note - this assay gives unreliable results on urine samples and should only be used for pregnancy testing in serum (Clinical Chemistry 56:1839-1844, 2010)
2. No significant cross-reactivity is detected with an LH level of 1000 IU/L.
3. Calibrated against the WHO 3rd International Standard 75/537
4. Minimum detection limit of 1 IU/L.
5. According to the assay manufacturer, serum levels of hCG are below 2.9 IU/L in 95% of healthy, non-pregnant females (2).
This assay is suitable for pregnancy testing at or slightly before the time of the first missed menstrual period. During the first six weeks of normal pregnancy, serum levels of hCG can be expected to double every 1.5-2.5 days. To confirm pregnancy, it may be helpful to repeat the test after 3-5 days. hCG levels vary widely between individuals, and "normal" ranges during different stages of gestation are difficult to define.
Levels in an ectopic pregnancy are often lower than in normal intrauterine pregnancy (3). See Normal Range information for expected levels of hCG in normal pregnancy.
WARNING: Causes of increased hCG levels other than pregnancy:
1. Increased hCG levels can also occur in non-pregnant peri-menopausal or post-menopausal women, in patients with gestational trophoblastic disease or other tumors, following previous injection of hCG, and in patients with heterophile antibodies or other substances that cause false positive elevations in hCG immunoassays (3,4).
2. Non-pregnant peri-menopausal and post-menopausal women can have hCG levels up to at least 14 IU/L and these women also generally have FSH levels > 20 IU/L (5,6).
3. If gestational trophoblastic disease or non-trophoblastic tumor is suspected, an elevated serum hCG should be confirmed by urine hCG testing.
WARNING: False positives
1. An elevated serum hCG with a negative urine hCG suggests the possibility of a false-positive result in the serum assay and should not be relied upon for diagnosis of gestational trophoblastic disease or tumor.
2. Increased serum hCG with negative urine hCG can also occur in very early pregnancy or abnormal pregnancy such as ectopic pregnancy, blighted ovum, or miscarriage.
3. In addition to a negative urine hCG test, characteristics of false-positive serum measurements may include low-level positive results (generally < 1000 IU/L and usually < 150 IU/L) that fail to show substantial changes in time with serial testing.
4. A negative serum result obtained by a different testing methodology should also increase suspicion for a false-positive initial test.
Therefore, when a false-positive serum hCG result is suspected, the following options should be considered:
1. Check of urine hCG (see HCG for Pregnancy, Urine). Urine hCG should be elevated in trophoblastic disease.
2. Measure serum hCG levels over several days or weeks and check for a trend in values. False positive results may show little variation over time. In contrast, hCG levels will increase during uncomplicated gestation or decrease after evacuation of trophoblastic tissue.
3. Increased hCG levels due to pituitary hCG in peri-menopaual and post-menopausal women can be suppressed by treatment for 3 weeks with a high-progesterone oral contraceptive pill (6). Elevated levels of FSH > 20 IU/L are also consistent with peri-menopause and post-menopause (5,6).
4. Request that the Clinical Laboratories measure serum hCG via alternative immunoassay method. Positive results in some assays but not others suggests the possibility of a false positive result due to an assay interference problem.
5. If questions persist about the possibility of a false positive result, request measurement of serum hCG by multiple methods and detection of hCG variants through the USA hCG Reference Service, Department of Obstetrics and Gynecology, University of New Mexico (see www.hcglab.com for specimen collection and billing information).
(a) Processing for these studies requires 10 mL of serum and 10 mL of urine collected in parallel.
(b) Blood should be collected in Red-top tubes.
(c) This testing must be coordinated through the Laboratory Medicine resident in Chemistry x3-1469.
(d) An information form, clinical history, and previous hCG test results should be provided.
(e) Serum samples are shipped Monday through Thursday for testing.
1. Cole LA, et al. Selecting an appropriate hCG test for managing gestational trophoblastic disease and cancer. J Reprod Med 2004; 49:545-553.
2. Beckman Coulter Access Immunoassay Systems total beta-hCG package insert (2006).
3. Stenman U-H, et al. The classification, functions and clinical use of different isoforms of HCG. Hum Rep Update 2006; 12:769-784.
4. Braunstein GD. False-positive serum human chorionic gonadotropin results: Causes, characteristics, and recognition. AJOG Reviews 2002; 187:217-224.
5. Snyder JA. Diagnostic considerations in the management of hCG in aging women. Clin Chem 2005; 51:1830-1835.
6. Cole LA. "Background" hCG in healthy, non-pregnant women. Clin Chem 2005; 51:1765-1766
|Last Updated||11/16/2012 12:19:40 PM|
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