Information about Blood DNA Testing

Is blood a more accurate sample than saliva for DNA testing?

A common misconception is that blood DNA testing is more reliable than performing a DNA test through saliva. Clients looking to perform a paternity test think that sending in blood DNA for their test will increase the accuracy of the test. This is of course incorrect since performing a DNA test through blood will give the same accuracy as performing it with any other sample that contains DNA including hair DNA. It is therefore important to understand that once enough DNA is obtained from the blood, swab, hair or semen, the DNA profile is the same throughout and will give the same paternity test result.

Another issue relating to blood DNA testing is that taking the samples can be an uncomfortable and even painful experience. Obtaining the blood requires the drawing of blood which can be a problem when you have to take it from children. Taking a saliva sample though an oral swab clearly is a much simpler process and can be done by the client themselves at the comfort of their own residence. This is one of the main reasons why a paternity blood test has now been replaced by the use of oral swab testing.

Can I use blood grouping to confirm paternity as opposed to a DNA test?

The answer here is a definite NO. Blood grouping does not give the level accuracy of a paternity test since the power of exclusion for blood testing is only 30%. Before the advent of DNA testing, this method was the only one available for exclusion of paternity. However, as DNA testing technology developed it clearly superceeded this technology. With an accuracy level of 99.999% in cases of inclusion of paternity and a 100% exclusion rate, DNA paternity testing is clearly the best technology available to date.

If I want to use Blood DNA anyway how do I send it?

Blood DNA testing is normally performed through the use of FTA filter paper. This paper is specifically designed to collect blood spots and facilitate its extraction to complete the DNA test. Only a few drops of blood are required. If the laboratory offers this service and it is requested, they will normally include the FTA paper in their DNA kit together with lancets to prick the finger and alcohol swabs. It is recommend to read the instructions carefully to ensure that the blood DNA is collected properly.

Step 1         -         Step 2

Before starting the blood DNA test collection procedure arrange the lancets, alcohol swabs, FTA paper and Tamper Seal.  Write the names of the individuals being tested next to the circle on the FTA card where their sample will be placed.

Step 3         -         Step 4

Carefully remove the round safety cap from one of the blood lancets.  Begin collection process by gently pressing the lancet into the index finger.

Step 5         -         Step 6

Drop the used lancet into the cup with the household bleach or hydrogen peroxide.  Gently squeeze the finger until a pea size blood droplet forms.  Apply the blood spot firmly to the FTA card within the circled area.

Step 7         -         Step 8

It is not necessary to completely fill the circle with blood.  Swab punctured finger with the provided alcohol swab. Use firm pressure until bleeding stops.

Step 9         -         Step 10

Attach the Tamper Seal firmly over the area where seal flap seals to the envelope, and add the sample collector’s initials to the envelope.  Non-Legal Tests: Complete the GTL - Sample Documentation and Consent Form.

Step 11

Package everything in the padded envelope and send off for your paternity blood DNA test.