Protocol - Current Pregnancy Status - Bioassay

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Human chorionic gonadotropin (hCG) is a hormone the placenta produces shortly after fertilization. Within 7-10 days of conception, hCG can be detected in urine or blood samples. Levels of hCG rise quickly through early pregnancy and peak at 10-12 weeks in the 100,000 to 200,000 mIU/mL range. Standard urine collection procedures from the National Childrens Study are described in the protocol. An immunoassay was used during National Health and Nutrition Examination Survey (NHANES) to rapidly detect pregnancy in adolescents and adults.

Specific Instructions

A pregnancy test should be conducted if it is necessary to know whether or not the subject is pregnant for research or clinical purposes. The Pregnancy Working Group recommends using the Current Pregnancy Status - Self-Report protocol in a setting in which knowledge of pregnancy status is not vital to the study itself (i.e., no fetal/maternal risk if the participant was identified as non-pregnant by self-report when in fact she was pregnant.) The Current Pregnancy Status - Bioassay protocol is recommended when pregnancy status is vital to the study or if there is any potential risk to the participant or fetus if the participant is pregnant.

The ICON® 25 hCG (Urine/Serum) test kit was used for National Health and Nutrition Examination Survey (NHANES) but other text kits or pregnancy test devices may also be used.





An immunoassay or pregnancy test kit can be used within a few days of the woman’s missed menstrual period.

Exclusion Criteria


Sample Collection Procedures

Follow standard urine collection procedures. Ask the woman to self-collect a urine sample, preferably a first morning void sample in a sterile 120 ml urine collection container with a screw-on lid. Label the urine sample. Since only a small amount of urine is needed for the pregnancy test, the remainder of the sample may be used for additional analyses. The detailed sample collection procedures from the National Children’s Study are available here.

Record the Results of the Urine Collection Procedure

Record the date and time that the urine sample was collected. If the woman was unable to collect a urine sample or refused, record this information.

Pregnancy Test Procedures

There are multiple ways to perform a pregnancy test with a urine sample. Two of the most common methods, which are both accurate, and quantify human chorionic gonadotropin (hCG), are an immunoassay test kit and a digital pregnancy test device. Never use an expired immunoassay kit or device.

NHANES utilizes an immunoassay test kit which can be performed on either a urine or a serum sample. The immunoassay test includes quality control procedures which would need to be completed by a trained technician. See Chapter 5 of the NHANES Lab Procedures Manual here for the entire testing protocol.

Women may self-administer a digital pregnancy test device. If this method is chosen, utilize the most accurate FDA approved device available.

Record the Test Results

Record the results as positive, negative or invalid.

If the immunoassay or device quantifies the hCG concentrations, record the results in mIU/mL.

The NHANES immunoassay quantifies hCG in a urine or serum sample at the sensitivity of 25 mIU/mL. Other glycoproteins do not affect the results of this immunoassay.

NOTE: If a woman has just missed her period by 1-2 days, the test should be repeated in 7-10 days.

Reference Values

NHANES immunoassay results of 25 mIU/mL hCG or more are indicative of a positive pregnancy test. Digital devices may have lower or higher thresholds for a positive test.

Personnel and Training Required

The sample processing and analyses should be performed by a certified laboratory technician.

Equipment Needs

A relatively inexpensive and easy to use immunoassay kit or digital pregnancy test device may be used to determine if the woman is pregnant.

Requirement CategoryRequired
Major equipment No
Specialized training No
Specialized requirements for biospecimen collection No
Average time of greater than 15 minutes in an unaffected individual No
Mode of Administration



Adolescent, Adult, Pregnancy


Examined female participants aged 12-59 years, and menstruating females aged 8-11 years were eligible. However, due to disclosure risks, only females 20-44 years have urine pregnancy results.

Selection Rationale

The National Childrens Study (NCS) was one of the largest pregnancy cohort studies in the United States, and the biospecimen collection methods have been validated in other studies.

This is a sensitive assay to measure human chorionic gonadotropin (hCG) in human urine. The National Health and Nutrition Examination Study (NHANES) is a major cross-sectional study in the United States, and the method has been validated on other studies.



caDSR Form PhenX PX240601 - Current Pregnancy Status Bioassay 6873106 caDSR Form
Derived Variables


Process and Review

Not applicable.

Protocol Name from Source

National Health and Nutrition Examination Survey (NHANES) Mobile Examination Center (MEC) Laboratory Procedures Manual, 2013-2014


Centers for Disease Control and Prevention. (2013-14). National Health and Nutrition Examination Survey (NHANES), Chapter 5 of the MEC Laboratory Procedures Manual. Atlanta, GA: Author.

Eunice Kennedy Shriver National Institute of Child Health and Human Development. (2014). National Children’s Study, Biospecimen adult urine procedures: Standard operating procedures. Bethesda, MD: Author.

General References

Blehar, M. C., Spong, C., Grady, C., Goldkind, S. F., Sahin, L., & Clayton, J. A. (2013). Enrolling pregnant women: Issues in clinical research. Women’s Health Issues , 23(1), e39-e45.

Protocol ID


Export Variables
Variable Name Variable IDVariable DescriptiondbGaP Mapping
PX240601050000 Has the patient just missed her period by more
1-2 days? show less
PX240601020100 When was the urine sample collected? Date N/A
PX240601020200 When was the urine sample collected? Time N/A
PX240601040000 What are the results of the pregnancy test? N/A
PX240601030000 Was an immunoassay test kit or a digital more
pregnancy test kit used? show less
PX240601010000 Was the collected urine sample a first more
morning void sample? show less
Measure Name

Current Pregnancy Status

Release Date

January 31, 2017


This measure is used to determine if a woman is currently pregnant or not.


A biological assay is the most accurate pregnancy test. It may be important to know whether or not a woman is pregnant prior to some tests (e.g., dual-energy X-ray absorptiometry) or to the use of pharmaceutical agents as in a clinical trial. In addition, pregnancy may influence the results of several physical and health measures such as weight, blood pressure, stress, and depression. This measure can also be used to make a determination of whether the subject can be included or excluded from a research study or whether she should be excluded.


pregnancy, pregnant, National Children’s Study, NCS, National Health and Nutrition Examination Survey, NHANES, Centers for Disease Control and Prevention, CDC

Measure Protocols
Protocol ID Protocol Name
240601 Current Pregnancy Status - Bioassay
240602 Current Pregnancy Status - Self-Report

There are no publications listed for this protocol.