When is guthrie test performed

Keep logged in. Cookies deactivated. To use all functions of this page, please activate cookies in your browser. Login Register. Additional recommended knowledge. Topics A-Z. All topics. To top. About bionity. Your browser is not current. Microsoft Internet Explorer 6. Your browser does not support JavaScript. To use all the functions on Chemie. DE please activate JavaScript. Guthrie test The Guthrie test , also known as the Guthrie bacterial inhibition assay , is a medical test performed on newborn infants to detect phenylketonuria , an inborn error of amino acid metabolism.

Bacterial inhibition assays are tests in which scientists use bacteria to measure the concentration of a substance in a sample. Guthrie then placed blood samples, dried on thick filter paper, onto that gel.

If the blood sample contained phenylalanine, B. If the sample of blood did not contain phenylalanine, B. Guthrie noted that a single technician could test one to blood samples in a single day and that each test required only a finger prick of capillary blood on a filter paper disc. After developing the test and showing it to Warner, Guthrie tested the sensitivity of his bacterial inhibition assay using normal blood samples spiked with phenylalanine.

Sensitivity is the ability of a test to detect all cases where the disease is present. Guthrie added 2, 4, 8, 12, and 20 milligrams of L-phenylalanine per milligrams of blood serum to normal blood samples to mimic the levels of phenylalanine found in patients affected with PKU.

He incubated those dried blood samples with the added L-phenylalanine overnight on the bacterial inhibition assays and found that bacteria had grown around the paper discs. He determined that bacterial growth spiked in the samples containing 12 and 20 milligrams of phenylalanine per milligrams of serum, meaning that those samples indicated an individual possibly had PKU and should undergo further blood testing.

After evaluating his test in the lab, Guthrie compared the results of his test and of the ferric chloride urine test on 3, specimens from the Newark State School in Newark, New York. Then, Guthrie confirmed all positive cases determined by the Guthrie test and ferric chloride urine test with a quantitative blood assay.

He compared the results of the Guthrie test to the results of the ferric chloride urine test and their sensitivities for detecting the disease accurately. Guthrie found that his test detected twenty-one positive cases of PKU that were also confirmed by the quantitative blood assay, and the ferric chloride urine test only detected seventeen of those cases, meaning that the ferric chloride urine test failed to detect four cases of PKU.

According to Guthrie, those data suggested that his test could be used to detect new cases of PKU in populations already screened using the ferric chloride urine test. Guthrie then refined his method by making the blood collection more convenient for doctors. If doctors diagnosed patients earlier, patients could implement a protein-restricted diet before the amino acid phenylalanine rose to toxic levels in the blood and caused irreversible neurological damage.

After his test's initial success, Guthrie modified his bacterial inhibition assay so that infants could be tested a few days after birth. To do so, Guthrie determined whether or not a small collection of capillary blood from an infant's heel would work on the bacterial inhibition assay. He made cards, later called Guthrie cards, which were thick filter papers, each with a metal blade that punctured an infant's heel and collected the resulting blood.

He let the blood dry directly on the card and saved it for testing. From the card, he then hole punched a round paper disc of the blood to be placed later on the agar gel culture. Guthrie found that the bacterial inhibition assay worked with infant's heel blood. The younger sister, Kammy McGrath, was diagnosed with PKU by the Guthrie test and treated early in her life, thus avoiding mental disabilities.

In the fall of , the National Association of Retarded Citizens publicized the Guthrie test at their press conference in San Francisco, California, and Life Magazine published an article on Guthrie and his newborn screen the following year. Guthrie and his team tested , infants for PKU using the Guthrie test and the ferric chloride urine test. Guthrie and his team diagnosed thirty-seven cases of PKU in two years. Of those infants presumed positive for PKU, thirty-seven cases of PKU were confirmed by repeating the Guthrie test and using a quantitative blood assay, meaning the test was effective.

In , Guthrie entered a contract with Ames Company in Elkhart, Indiana, a division of Miles Laboratories, to produce and market Guthrie test kits to hospitals. However, Ames Company stipulated that they would only enter a contract if the test received a patent. Guthrie filed for a patent on the Guthrie test in his own name in He then signed an exclusive licensing agreement with Ames Company.

The licensing agreement granted Guthrie no royalties, meaning that Guthrie would not make any money from the test kits sold. Guthrie did not stipulate what price the kits should be sold at in the contract. After signing the contract, Ames Company struggled to produce enough test kits to meet demand. An abnormal result is not confirmation that your child has a condition. The bloodspot test is a screening test. As such, it identifies babies who are at increased risk of a condition.

Diagnostic testing and an examination by a specialist will be needed to determine whether your baby has that condition. This further testing needs to be performed as early as possible so if treatment is needed, it too can begin as soon as possible. Commonwealth Privacy Legislation and hospital and PathWest policies protect the confidentiality of all information regarding babies and their test results. Newborn bloodspot screening has been shown to be reliable but as with any laboratory test, false positive and false negative results can occur.

For this reason, screening alone should never be used to rule out the possibility of a child having a condition. If you have any suspicion your baby may have a health condition, you should follow up immediately. The screening test for cystic fibrosis, for example, will detect only 95 per cent of babies with the condition. The test may also detect a small number of healthy babies who carry the gene for cystic fibrosis.

Detailed information about the conditions screened for by Newborn Bloodspot Screening Program can be found on the WA Department of Health website external site. If you need help with translating the information on these sites, call the Translating and Interpreting Service on This publication is provided for education and information purposes only.

It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional.

Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.

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