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Human Chorionic Gonadotropin for Tumor, serum
|Performed by||China Basin Chemistry|
|In House Availability||Monday, Wednesday and Friday (day shift)|
|Method||DPC Immunlite 2000 Immunochemiluminometric assay (ICMA)|
|Container type||Gold top or Light Green top|
|Amount to Collect||1 mL blood|
|Sample type||Serum or plasma|
|Preferred volume||0.5 mL serum or plasma|
|Min. Volume||0.25 mL serum or plasma|
|Processing notes||Freeze specimen at -20C.|
|Synonyms||HCG; Beta-HCG; b-HCG; molar pregnancy; tumor marker|
|Turn around times||1-3 days|
|Additional information||Assay Information:
1. This test detects all major hCG variants including intact hCG, nicked hCG, free beta hCG subunits, hyperglycosylated hCG, hCG beta core fragments, hCG minus the C-terminal extension, and pituitary hCG (1,2).
2. No cross-reactivity is detected with an LH level of 16.5 ng/ml.
3. The assay is calibrated against the WHO 3rd International Standard 75/537 and has a minimum detection limit of 1 IU/L.
4. According to the assay manufacturer, serum levels of hCG are below 1.1 IU/L in 95% of healthy males and below 2.7 IU/L in 95% of healthy, non-pregnant females (3).
The use of this test for hCG tumor monitoring was evaluated by the Clinical Laboratories at the Medical Center at UC San Francisco. It has not been cleared or approved by the U.S. Food and Drug Administration for use as a tumor marker.
Warning about false positive hCG results and other causes of elevated serum hCG:
Elevated levels of serum hCG can occasionally lead to incorrect diagnoses of gestational trophoblastic disease or non-trophoblastic tumor. Increased hCG levels also occur in pregnant women, non-pregnant peri-menopausal or post-menopausal women, patients recently injected with hCG, patients with heterophile antibodies or other substances that cause false positive elevations in hCG immunoassays, and in infants less than 3 months of age (4,5). 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 (6,7).
If gestational trophoblastic disease or non-trophoblastic tumor is suspected, an elevated serum hCG should be confirmed by urine hCG testing. An elevated serum hCG with a negative urine hCG suggests the possibility of a false-positive result in the serum assay due to heterophile antibodies or other non-hCG substances and should not be relied upon for diagnosis of gestational trophoblastic disease or tumor. 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.
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. 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 (7). Elevated levels of FSH >20 IU/L are also consistent with peri-menopause and post-menopause (6,7).
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 requires 10 mL of serum and 10 mL of urine collected in parallel.
(b) Blood should be separated in red-top tubes
(c) This testing must be coordinated through the Laboratory Medicine resident in Chemistry 353-1469.
(d) An information form, clinical history, and previous hCG test results should be provided. Samples are shipped Monday through Thursday for testing.
1. Cole LA, et al. Between-method variation in human chorionic gonadotropin test results. Clin Chem 2004; 50:874-882.
2. Cole LA, et al. Selecting an appropriate hCG test for managing gestationalReprod Med 2004; 49: 545-553.
3. Immulite 2000 HCG package insert (2005).
4. Braunstein GD. False-positive serum human chorionic gonadotropin results: Causes,characteristics, and recognition. AJOG Reviews 2002; 187:217-224.
5. Stenman U-H, et al. The classification, functions and clinical use of differentbisoforms of HCG. Hum Rep Update 2006; 12:769-784.
6. Snyder JA. Diagnostic considerations in the management of hCG in aging women. Clin Chem 2005; 51:1830-1835.
7. Cole LA. "Background" hCG in healthy, non-pregnant women. Clin Chem 2005; 51:1765-1766.
|Medical Necessity?||Yes. Click here for more information|
|LDT or Mod FDA?||Yes|
|Last Updated||8/9/2013 8:55:47 AM|
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