Urine hCG

What is Urine hCG?

The urine pregnancy test is based on the ability to detect low levels of a hormone, Human Chorionic Gonadotrophin (hCG), in the urine during early pregnancy. hCG is made by the rapidly dividing cells that develop from the fertilised egg and specialise to become the placenta. As the growing embryo and placenta travel along the fallopian tube to implant in the uterus during a normal pregnancy, the hCG levels circulating in the blood double every 2 – 3 days, levelling off after the first 10 – 12 weeks.

A laboratory test for serum hCG level can reliably measure the level of hCG about one week after conception. A point of care test for urine hCG produces a positive result about 3 days later because of the relative sensitivity of the test, the need for hCG to filter into the urine, and the volume of urine that can sometimes dilute the hCG.

It is important to realise that a urine pregnancy test can therefore sometimes give a ‘false negative’ result and miss pregnancies at a very early stage. Operator errors in performing the test can also lead to false negative results.

'False positive' urine pregnancy test results are possible and may cause confusion, particularly when a woman has recently been pregnant and has then miscarried. Be aware also that hCG levels can be ‘positive’ in conditions not associated with pregnancy. Device errors may also lead to false positive results.

The urine pregnancy test is a quick, convenient and cost-effective way to check if a woman is pregnant. But to ensure consistently accurate results at the boundary between ‘negative’ and ‘positive’ hCG levels, and to minimise the number of pregnancies that are missed using the test, it is vital that the performance of the device and the integrity of the reagent strips are regularly checked.

So how can you be confident that your device is giving the right result every time it’s used?

How can you be sure that your device continues to work as the manufacturer originally intended?

There are 3 key steps that you can take to assure the quality of your results:

Know what you are doing
  • Healthcare Professionals should always be trained by the device manufacturer or local laboratory staff and be certified as competent to perform the test.
  • Make sure you have read and understood the instructions supplied with your testing device.
  • Pay attention to any limitations that may be listed – this means that the device may not be suitable for:
    • Patients with certain disease conditions
    • Patients taking certain medications
    • Certain types of sample e.g. random urine vs early morning urine
    • Certain types of sample collections tubes (e.g. added preservatives)
  • Make sure your consumables and quality control solution (if used) have not passed their opened or unopened expiry dates.
  • Make sure you are storing the test cartridges and quality control solution at the right temperature.
    • Storing the cartridges at the wrong temperatures can lead to inaccurate results.
  • Ensure any required routine maintenance is carried out (e.g. cleaning)
Use Quality Control
  • The manufacturer of your device may provide small bottles of Quality Control (QC) solution or you may be able to purchase them independently. You can analyse these solutions as if they were a patient sample and the documentation accompanying solution will state what result you should obtain.
  • The result you obtain for this QC solution should fall within the range/criteria of results quoted by the manufacturer.
  • When you run a QC test, you will know instantly whether the result is acceptable or not. Achieving good QC results will give you immediate information and the confidence to continue to use your device and act upon the results.
  • If your QC results are not within range, follow the manufacturer's instructions to troubleshoot this problem – do not continue to use the device for patient testing.
Use Qpoint External Quality Assessment
  • Participation in an External Quality Assessment Scheme or "EQAS" such as Qpoint for your device is recommended by the Medicines & Healthcare Regulatory Agency (MHRA) in the UK1.
  • When you enrol and participate in Qpoint, you are sent a monthly sample of urine to test on your device. You do not know what the correct result should be.
  • You then submit your result to Qpoint, who compare your result to the results that other users of the same device have submitted for the same test sample.
  • There may be many of users of the same type of device registered with the scheme from around the UK, or internationally, that your result will be compared to.
  • The following month, when you receive your next test sample, you will also receive a report that tells you how well your previous result agreed with all other users of the same device registered with our scheme.
  • The Qpoint report is easy to understand and gives advice on any action that you may need to take to improve the quality of your results.
  • If your EQA test results are in good agreement with other users of the same device you will have reassurance that your device and consumables are working as they should under your own local conditions. It also gives you confidence that your testing procedures continue to meet the manufacturer's specification.
  • The Qpoint organisers work independently of device manufacturers, but when problems are identified with any particular instrument, the manufacturer is advised and encouraged to address the issue.
  • Any serious problems identified are reported to the MHRA.

1 MHRA Device Bulletin: Management and Use of IVD Point of Care Test Devices. DB2010 (02) February 2010

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