Heel prick test in babies: what it is and what it's for

One of the tests your baby will have in hospital before you are discharged is the heel prick test. And so that you know exactly what it involves, here at Happymami we bring you this post, where you will find everything you need to know about the heel prick test.

Discover the heel prick test

What does the heel prick test involve?

The heel prick test involves taking and analysing a few drops of blood from the newborn's heel to detect the presence of certain congenital conditions. Its aim is to detect serious conditions from the very first moment, most of which are rare and genetic in origin. This means that appropriate treatment can be started early to avoid long-term problems and guarantee a better quality of life for the baby. These conditions are very rare genetic and/or endocrine disorders, but they can appear from the moment the baby is born, even if no symptoms have appeared yet.

What are congenital conditions?

Congenital conditions are conditions present from birth. That is why detecting and treating some of them early on improves their outcome. Likewise, the conditions included in the early detection programme carried out through the heel prick test have a treatment which, given early, can prevent or reduce the symptoms and damage that would occur without the right intervention.

Which congenital conditions does the newborn screening programme detect?

In this section, it depends on the autonomous community. In Valencia, for example, the following are detected: congenital hypothyroidism, phenylketonuria, sickle cell anaemia, cystic fibrosis, medium-chain acyl-CoA dehydrogenase deficiency, long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency, glutaric aciduria type I and biotinidase deficiency; the latter is the most recent addition to screening in the Valencian Community.

When and how is the heel prick test carried out?

A sample of blood from the heel is taken on the maternity ward before discharge, 48 hours after the baby is born, or whenever between 24 and 72 hours have passed since the birth at that moment. It involves a superficial prick on the outermost part of the newborn's heel. A few drops of blood are collected and applied to both sides of an approved absorbent card. This card soaked in the baby's blood is sent to the laboratory for analysis.

In addition, along with the blood sample, family data is collected, from both the mother and the newborn, and calculations are made with it to determine whether or not the condition is detected. The data taken into account include the type of feeding of the newborn, whether you breastfeed your baby or use formula. The baby's gestational age at the time of birth, the weight of the baby, or whether the mother has received a blood transfusion or has hypothyroidism also have an influence.

How is the heel prick test carried out?

The nursing staff are trained to carry out this test. Beforehand, they prepare the necessary material (specific puncture lancet, sterile gauze, antiseptic, sucrose and absorbent paper). The lancets used for the prick are designed to make the exact incision, causing the least possible impact on the baby, with a clean cut that causes the baby the minimum sensation of pain. There is also the option of carrying out the test while the mother is breastfeeding, so that the baby benefits from breastfeeding analgesia.

To carry it out, the baby is positioned with the leg below the level of the heart to increase venous flow. A massage is given and a check is made that the baby is at a comfortable temperature. To carry out the prick, a gentle massage is given, hands are washed hygienically before putting on gloves and then the baby's heel is pricked. The paper must be filled with blood in such a way that it does not come into contact with the filter paper circles, as this could alter the test results.

Does the heel prick test hurt the baby?

Although the lancets used for the heel prick test are specially designed to prevent pain, there are different alternatives that help the test to be better tolerated by babies. There is evidence to suggest that the presence of the mother (holding her child in skin-to-skin contact or breastfeeding during the process) means the little one shows less discomfort. If for any reason the mother cannot be present at the time of the test, sucking on a dummy also reduces the pain.

How long does the test take and how will I find out the results?

The test lasts just a few minutes and the results are received at around three weeks. A normal result, which is the case in most instances, because the conditions screened for are rarely suffered by babies, will be sent by post to the parents or guardians within approximately one month of the sample being taken. If the result is unclear or there is a suspicion of one of these conditions, or the sample is insufficient to carry out all the tests, the laboratory will contact you by telephone and tell you where to go and which tests need to be carried out.

If the results of these tests are normal, can your baby still have the condition?

A normal heel prick test result indicates that the probability of having these conditions is extremely low. However, it does not rule them out completely.

If my baby has one of these conditions, where will they be diagnosed and treated?

For example, in the Valencian Community there are several reference services and units in the hospitals, which have the necessary resources to offer a correct diagnosis and treatment. The same applies to every community.

Finally, is it compulsory?

Carrying out this test is strongly recommended, but not compulsory. As mum and dad, after informing yourselves, you must sign on the form attached to the sample collection to give your authorisation or refusal for the test to be carried out.

Special situations to bear in mind

There are circumstances that contraindicate carrying out the test, for example in babies whose heels are both oedematous, injured or infected. In these cases, or in any case where the heel prick test is contraindicated or cannot be carried out for any reason, a venous blood sample from the baby is recommended.

Also, in premature newborns and/or babies admitted to intensive care, the harm/benefit of making the incision in the heel can be taken into account, or an arterial/venous blood sample can be taken if they have an umbilical catheter. A venous prick during another blood test can also be used. And if the baby needed a blood transfusion, whenever possible the test should be carried out before the transfusion, even if the 48 hours of the baby's life have not yet passed. And the test should be repeated when appropriate, depending on the type of transfusion.

Brief description of the conditions detected by the programme

Congenital hypothyroidism

Babies with this condition do not produce enough thyroid hormone. Although they usually have no symptoms at first, if it is not treated by giving the necessary hormone, the hormone deficiency affects their physical and mental development, causing severe disability.

Phenylketonuria

This is a genetic condition of amino acid metabolism, specifically of phenylalanine. Without the necessary dietary treatment, it causes severe and irreversible intellectual disability, as well as other neurological symptoms.

Sickle cell anaemia

This is a genetic condition in which there are mainly problems with the respiratory and digestive systems. Early detection and treatment improve the nutritional status, growth, lung function and survival of these babies.

Medium-chain acyl-CoA dehydrogenase deficiency

This is a genetic condition affecting fatty acid oxidation. Although around 30% of detected cases are asymptomatic or mild forms, there are other forms that cause severe episodes of metabolic decompensation. Most occur before the age of 4 with severe neurological consequences that can be avoided with preventive treatment in the form of dietary measures.

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency

This is a genetic condition related to fat oxidation. The deficiency of this enzyme prevents the body from processing the food the baby eats or the fat stored in their body.

Early identification and dietary treatment prevent the metabolic decompensation that causes heart problems and eye, liver, muscle and nerve damage.

Glutaric aciduria type I

This is a genetic condition of amino acid metabolism. These patients have difficulty using and eliminating the proteins they take in, which therefore build up in the body and cause irreversible damage. Around 90% of patients develop neurological conditions during the period of brain development (from 3 to 36 months of age)

Newborn diagnosis and early dietary treatment, with a diet free of lysine and low in tryptophan, considerably reduce neurological symptoms, feeding and breathing problems and seizures.

Conclusion: everything you need to know about the heel prick test

You know that at Happymami we always aim to offer you the best and most up-to-date information, and that our team of midwives will be delighted to advise you if you need anything. Prevention is the best approach with these conditions, and these programmes prevent greater problems.