(Blood Collection) Heel Stick for Neonatal Screening Test Procedure
Heel Stick for Neonatal Screening Test Procedure
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Many children have to face disabilities and premature death due to various metabolic and genetic diseases that can be prevented by early diagnosis and treatment. Newborn screening programme is a step to ensure that these diseases do not go undiagnosed in the early stages and individualized management programmes can be devised for such children.
Image 1: procedure of neonatal heel prick.
History and Uses
This test was devised by an American physician and bacteriologist Robert Guthrie and it was first used in 1962.The test initially was based on bacterial inhibition assay but now new technologies like tandem mass spectroscopy are being used for newborn screening (Behrman et al, 2012).
It is estimated that by use of newborn screening there is an increase of approximately 32% in the diagnosis of children affected with various disorders (Behrman et al., 2012). This procedure is also important as these infants are apparently normal at birth and may be diagnosed late in life when the disease has caused irreversible damage.
Though there are variations in the list of diseases covered in the screening in different countries and states (Cloherty et al., 2011) the following major diseases are included:
Galactosemia and Phenylketonuria
Hemoglobinopathies and cystic fibrosis.
Amino acid, fatty acid and organic acid disorders.
Equipments required for performing the procedure
1. Documents related to the identification and health record of the neonate. 2.Blood spot and glassine envelope.
3. Non sterile protective gloves. 4. Cotton wool and micropore.
5. Automated lancet devices. 6. Sharps box.
7. Stamped envelope for sending samples to screening lab.8.Water swab (Guidelines for Blood spot sampling, 2012)
Image 2: Lancet devices.
Procedure of performing heel prick in neonates
Before beginning the procedure parents must be informed about the procedure and an informed consent noted in maternity and hospital records. If parents decline the test reasons for the same must be noted and the blood spot card marked as decline and sent to the screening lab. The blood card should always be placed on a clean surface and correct personal details about the baby filled at appropriate places along with records of any relevant family or medical history.
Comforting the baby and timing of test
The baby should be comforted using breast feeding, swaddling, non nutritive sucking, using glucose solutions and face to face contact during the procedure. The test is usually done at day 5 -8 of life and the day of birth is counted as day 0.
Cleansing and warming of heel
The heel should be cleaned with water and in case of fecal contamination by mild non perfumed soap to avoid contamination by immunoreactive trypsinogen which is present in fecal matter and whose evaluation is used as a screening test for cystic fibrosis. The heel should be completely dry before making the prick. There is no need for additional warming of the heel if the infant is warm and in no condition should alcohol be used for cleaning.
Site of puncture
Automatic lancet devices are used for puncture and they should be placed against the skin as prescribed by the manufacturer. The site of the puncture in full term and pre term infants is the shaded area in the following figure and is somewhere between outer and inner limit of calcaneum. The depth of the incision should not be more than 2mm.
Image 3: Site of heel prick.
The drops of blood are then collected in such a manner that the circles on the blood card which is a special kind of filter paper are completely filled. The heel should not be squeezed to increase blood flow and there should be only one layer of blood on the card. If needed a second prick may be performed. Once the required sample is collected then the site of the puncture should be cleaned and pressed by a cotton wool and covered by a plaster which can be removed later.
Image 4: blood spot card
Transport of sample and procedure in screening lab
After collection of the sample the card should be allowed to dry thoroughly and then sealed in the glassine envelope and sent to the designated screening lab as soon as possible or at least within 24 hours of collection. Once the samples reach the screening lab they are subjected to various tests like growth on specialized agar plate to test for Phenylketonuria. Immunoassays for thyroid hormones to detect congenital hypothyroidism, galactosemia and biotinidase deficiency can be detected by using enzyme assays and molecular techniques can help in early detection of severe combined immunodeficiency and cystic fibrosis.
Once the results are known and if any abnormality is detected the designated personnel gets in touch with the doctor or the hospital involved and the baby is then called up for further confirmatory tests to corroborate the findings of the screening tests. False positives may occur and parents must always be kept in the loop about the results.
Newborn screening is potentially one of the most rewarding public health initiatives taken up by many countries. Timely detection of genetic and metabolic diseases can help prevent mental retardation, seizures, and disabilities and can also secure the health of future siblings. Though there are ethical issues involved with screening it still remains an important tool to safeguard our children.
Behrman RE., Kliegman RM.,Stanton FB.,SchorNF.,St.Geme JW., (2012). In Nelson Textbook of Pediatrics. Philadelphia: Elseivier. 537-538.
Cloherty PJ.,Eichenwald EC.,Hansen AR.,Stark AR., (2011). In Manual of Neonatal care. Philadelphia: Lippincot Williams & Wilkins. 105-106.
Guideline for Nerwborn Blood Spot Sampling. (2012). Retrieved from www.newbornblood spot.screening.nhs.uk.