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Human Chorionic Gonadotropin for Pregnancy, serum, ≥ 18 year old (Adult)

Item Value
Test Update Information Due to a change in standardization of the hCG serum pregnancy assay by the test manufacturer, results of the hCG for pregnancy assay will increase beginning on October 29, 2014. This change in assay standardization will cause results in the range of 5 to 1000 units to increase by approximately 10 to 20%, and results in the range above 1000 units to increase by approximately 20 to 40%.
Standardization changed from the WHO 3rd International Standard 75/537 to the WHO 5th International Standard (NIBSC Code 07/364).
Available Stat? Yes, for ectopic R/O only
Test code HCGPA
Test group HCG
Performed by Parnassus & Mt. Zion Chemistry
In House Availability
Parnassus 24 hrs per day, 7 days a week
Mt. Zion 0700-2300, 7 days a week
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 or Lt. Green top
Amount to Collect 1 mL blood
Sample type Serum or plasma
Preferred volume 0.5 mL serum
Min. Volume 0.5 mL serum
Units IU/L
Normal range
Normal (Non-pregnant) < 5 IU/L


Representative hCG ranges during normal pregnancy are summarized below and are based on values previously reported by the assay manufacturer for the method employing the WHO 3rd IS and that have been adjusted to reflect the increased levels in the new method employing the WHO 5th IS.

0.2-1 weeks 5-65 IU/L
1-2 weeks 65-650 IU/L
2-3 weeks 130-6500 IU/L
3-4 weeks 650-13,000 IU/L
4-5 weeks 1300-65,000 IU/L
5-6 weeks 13,000-130,000 IU/L
6-8 weeks 19,500-260,000 IU/L
8-12 weeks 13,000-130,000 IU/L
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.

Assay Information:

1. This assay recognizes the intact hCG, the β subunit of hCG, nicked intact hCG and nicked βhCG isoforms. The free alpha subunit and β-core fragment yield no detectable response

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. The following table describes the cross-reactivity of the Access Total βhCG (5th IS) assay:

Substance Concentration added (IU/L) hCG Concentration without Cross-Reactant (IU/L) hCG Concentration with Cross-Reactant (IU/L)
hLH 103 2.25 2.10
hFSH 1000 2.30 2.23
hTSH 1 2.44 2.53
hCG α-subunit 500 2.95 2.87


3. Calibrated against the WHO 5th International Standard (NIBSC Code 07/364).

4. Minimum detection limit of 1 IU/L.

5. Total βhCG concentrations were measured in human serum samples collected from apparently healthy non-pregnant females using the Access Total βhCG (5th IS) assay. Concentrations of total βhCG measured in 100% of samples were determined to be ≤ 11.6 IU/L. The observed ranges and 95th percentile of total βhCG concentrations are shown in the table below. (2)

Reference Population (Non-pregnant Females) N Median (IU/L) Range (IU/L) 95th Percentile [95% CI]
≥18 and <40 years 132 0 0-0.6 0.3 [0.2-0.4]
≥ 40 years 141 0 0-3.1 1.5 [1.1-2.9]
Post-menopausal* 134 2.8 0.1-11.6 7.7 [6.4-10.4]


*post menopausal status confirmed using circulating FSH and estradiol level. Source-Beckman Coulter Access Total bHCG 5th IS package insert.

Diagnosing pregnancy:

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.

References:

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 (5th IS) package insert (2013).

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
LOINC code 19080-1
Last Updated 11/16/2014 6:59:47 PM
Entry Number 1498
Lab Procedure Link Click here for Procedure
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