At-home medical diagnostic blood tests have been increasing in popularity. A phenomenon that is likely to continue with the surge in people looking for at-home COVID-19 antibody tests. There is no doubt that self-testing blood testing kits are convenient with no trip to the GP required and results delivered quickly, letting you know if you have anything to worry about. However, questions have been raised about how reliable these tests are. Could they give inaccurate results and false reassurance?
Are finger-prick blood tests reliable?
Traditional at-home kits require you to take a blood prick finger sample, whereas in a GP office or hospital a medical practitioner would usually take a venous sample (blood drawn from your veins). So what is the difference?
Finger-prick blood samples: To take a finger-prick sample a lancet is used to prick your finger. The blood drop from your finger is then collected for testing. It cannot be used for all blood tests, especially if a larger volume of blood is required.
Venous blood samples: Venipuncture or a venous sample is when a needle is used to take blood from a vein in your arm. The blood is collected in a tube and allows for a larger sample to be taken than from a finger-prick. These samples should only be taken by a phlebotomist who is trained and qualified to take the sample.
Finger-prick blood tests can give accurate results for some tests, however, only if they are collected correctly and an adequate sample volume has been obtained. Studies have found that venous samples taken by a medical practitioner/phlebotomist tend to give more accurate results due to people having difficulty taking their own finger-prick blood samples.
What can cause finger-prick blood samples to be inaccurate?
There are several problems that can occur when people take at-home blood tests using the finger-prick method:
Insufficient sample size: It can be hard to get enough blood from a finger-prick test for the blood test to be carried out. When a laboratory receives the blood it is spun to separate the blood cells and the liquid plasma. If the sample is too small then they will struggle to get enough plasma for testing.
Squeezing the finger to get enough blood: To get a large enough sample for your blood test people often have to squeeze or milk their finger. This, however, can lead to the red blood cells bursting, the haemoglobin then escapes and spoils the surrounding sample, known as a haemolysed sample. It can also occur if people scrape the finger on the side of the tube.
Variation of blood drops: A study found that variation between blood drops drawn from a single finger-prick can cause inaccurate results. It found that to get consistent results you needed to have six to nine drops combined to achieve consistent results, therefore finger-prick blood tests could skew results.
These errors are much less likely to occur with a venous sample from a vein taken by a healthcare professional.
Home blood kits in practice, do they provide accurate results?
Are at-home STI test kits accurate?
STI tests are now quite commonly carried out at home to help combat the embarrassment many feel when taking these tests. At-home HIV tests often only detect HIV antibodies (second or third-generation HIV tests). Whereas fourth-generation HIV tests normally used by healthcare professionals can detect the p24 antigen that can be detected in the first few weeks after infection. As a result if you are worried about a recent infection you should consider getting a test taken by a medical professional. If you do not want to go to a gp or clinic, VisitHealth have professionals that will visit you at home to take this test - 5th generation HIV test.
In terms of reliability studies into chlamydia and gonorrhoea tests found that untrained people were fairly good at taking their own samples, however, they tended to be better at taking saliva samples rather than blood samples. Inaccuracies occurred with the self-administered blood tests because they drew the blood incorrectly or misapplied it.
Should COVID-19 antibody tests be carried out at home and are they accurate?
There has been a big surge in postal COVID-19 home antibody tests with people wanting to know if they have had the virus. However, there was recent controversy as it was found that the manufacturers of these tests did not design them or guarantee them for use at home using a finger-prick sample method. The tests are designed to be used with a venous sample taken by a medical professional.
On the 26th May the Medicines And Healthcare Products Regulatory Agency (MHRA wrote to private laboratories in the UK asking them to pause processing self-collected finger-prick samples for coronavirus antibody testing. The MHRA made this request so they could review the end-to-end testing process to assess whether home sample collection and postal delivery was an accurate and safe way of testing for coronavirus antibodies.
Alternatives to postal finger-prick blood tests at your home
At VisitHealth, we offer venipuncture services where a trained medical professional will visit you at home to take a blood sample. If you have a kit and are struggling to take your own blood or worried about inaccuracy the medical professional can take your blood at home, and help you use your kit to ensure you get most accurate results.
We also offer a range of blood tests that we carry out and provide the results directly to you. You can see the range of tests we offer here or get in touch with one of our team and they will be able to help you find the right test for you. By using VisitHealth you get the same quality of test result taken by a trained professional but with the convenience of being able to order your private test online and have it carried out at home.