Treatments & Therapies

Dry blood test – treatment, effect and risks

Dry blood test

The American doctor and microbiologist Robert Guthrie introduced the dried blood test in 1963 , the Guthrie test, with which he was able to diagnose the metabolic disease phenylkenonuria (inability to break down the amino acid phenylalanine because an important enzyme in the body is missing) in newborns.

This screening method, in which a few drops of blood from newborns are dripped onto a special filter paper, is still used worldwide today. After drying the blood , the filter paper is placed on a nutrient-rich agar plate without phenylalanine and a certain type of bacteria is added to it.

These special bacteria can only multiply if there is a lot of phenylalanine in the dried drop of blood. This is how it is determined whether a newborn infant has the congenital metabolic disease and therefore needs a special diet . If detected early, these newborns can grow up normally on a strict phenylalanine-free diet without the risk of mental defects.

What is the dry blood test?

In later years, other factors in the blood for congenital metabolic diseases were recognized, so that today the routine screening of newborns between the 36th and 72nd hour of life for certain metabolic disorders using the dried blot spot test (DBS) is standard.

To catch a drop of blood with a special filter paper, the newborn only needs to be pricked briefly on the heel. The dried filter papers are sent to selected special laboratories, where they are simultaneously tested for more than 30 metabolic diseases using complicated but efficient analysis methods. Within hours or a few days, doctors and thus the parents receive the test results. For ethical reasons, only diseases that are diagnosed early and can be treated are included in newborn screening .

Nowadays, newborn screening with the dry blood test is mandatory in many countries, but not in Germany. Nevertheless, this screening procedure for newborns is also used by many parents in this country and is financed by the health insurance companies.

Function, effect & goals

The simplicity of taking blood for the dried blood test meant that this examination method was also established for older children with other diseases in order to save them the painful venous blood collection with a needle. Today, the DBS method is used in many areas of in-vitro diagnostics (examinations outside the body by taking blood, urine or saliva beforehand ), including for adults.A small prick of the finger is enough to drip enough blood onto the special filter paper. For example, the concentration of vitamin D in the blood is determined using the dry blood test. Low levels of vitamin D indicate certain conditions. Even if the patient is still symptom-free at the time of the examination, the doctor treating you can initiate therapy immediately.

Dry blood tests are sometimes used for therapeutic drug monitoring, in which doctors need to know whether the dose of a prescribed medication is correct in the blood. For the DBS procedure, the doctor can also give a patient home the equipment they need to prick a finger and collect blood. This allows drops of blood to drip onto the corresponding filter paper and allow them to dry over a longer period of time. He then brings them with him to the next doctor’s visit or sends them directly to the designated laboratory. In this way, it is also determined whether a patient is taking his vital medication, such as antiepileptics , correctly.

In this context, the individual dose setting of immunosuppressants is a particular focus for the dry blood test. In order to set the right concentration of medication after an organ transplant, patients often have to have their blood drawn at very short intervals. This is another advantage of the DBS method, in that the already weakened patient is only slightly stressed when the blood is taken.

It is also practical that usually only a very small piece of the blood dried on the filter paper is required for the laboratory test and therefore different tests can be carried out from the same drop of blood. The “blood cards” can be stored clean, dark and cool for many years. If desired, it can be checked even after a long period of time whether a certain parameter in the blood was abnormal in the past or not. In addition, this type of blood collection provides more security for the medical staff from puncture injuries (possible transmission of infection is thus further minimized).

Even the laboratory staff benefit from this type of examination, as it saves time and consumables in the pre-treatment of the blood sample. Whole blood in tubes requires extensive pre-treatment, which is more time-consuming and expensive.

Risks, side effects & dangers

However, this type of blood collection also harbors risks for subsequent laboratory tests. In particular, if the filter papers are given to the patients to take home, it cannot be ruled out that they use the utensils improperly and the respective filter paper becomes unusable.Bacterial contamination or other dirt also lead to unusable test results. Scientific studies show that for certain parameters, such as some hormones , the test results between venous blood and the dried blood test can vary greatly. The reason for this is, among other things, the different amount of hematocrit (percentage of erythrocytes in the volume of the blood) depending on the blood collection procedure.

Therefore, many clinical trials are underway using dried blood tests to improve their reliability for certain parameters. Where necessary, the analysis methods are adjusted or, if necessary, blood from the vein is recommended. There are now dry blood tests for certain pets and farm animals.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.