REPORT


Dr Rachel Carling is consultant scientist and Deputy Director of Biochemical Sciences at St Thomas’ Hospital, London.


evidence to suggest that where there is a lack of access to clinical services over a seven-day period, patients do not always experience parity of access to the optimum treatment or diagnostic test. This can result in delays to their treatment that can contribute to less- favourable clinical outcomes”. Dr Rachel Carling, consultant scientist and Deputy Director of Biochemical Sciences, explained that: “Although inherited metabolic diseases are a diverse group of disorders, many patients present acutely, often in early life. Without appropriate intervention and management, such disorders can result in permanent disability and many are life-threatening. Currently, UK metabolic biochemistry services are only available weekdays, 9.00 am to 5.30 pm. Outside of this, analysis of urgent samples relies entirely upon the goodwill and availability of a small number of highly specialised staff.” The following example provided by Dr Carling demonstrates why an out-of-hours metabolic biochemistry service would be beneficial. A previously healthy four-day-old baby became floppy, lethargic and started vomiting. He collapsed on day 5 and was admitted with suspected sepsis, but he deteriorated rapidly. The metabolic paediatrician suspected an inborn error of metabolism (IEM) and requested an urgent metabolic screen consisting of plasma amino acids, urine organic acids and blood spot acylcarnitines. These tests have minimum turnaround times (TATs) of four, six and two hours, respectively. On receiving the urgent request on


Good Friday, the laboratory made numerous telephone calls until a biomedical scientist agreed to go in on the Saturday to run the organic acids. This result was finally available at 7.00 pm on Saturday evening; 36 hours after the patient presented. Propionic acidaemia was diagnosed and treatment commenced.


DECEMBER 2013


It is clear that had a seven-day service been available it would have improved the patient’s care in this case. However, initial challenges to establishing a seven-day metabolic biochemistry service are that analysis takes too long, the laboratory is too small, and there are insufficient highly trained staff to support a formal seven-day service. A service developed in partnership between two laboratories could overcome these difficulties; GSTS Pathology and Great Ormond Street Hospital are working together to establish a collaborative metabolic biochemistry service that will provide analysis of urgent samples seven days a week. Professor Simon Heales from chemical pathology at Great Ormond Street Hospital said he is “delighted to be part of this collaborative project that has the clear potential to have a significant positive effect with regards to achieving timely diagnosis for children with life-threatening metabolic disorders”.


EXPANDED NEWBORN SCREENING SERVICE Over the past 30 years, the newborn screening programme has been highly successful in preventing significant mortality and morbidity. Every baby born in the UK is offered screening for five inherited disorders within their first week of life (ie phenylketonuria, congenital hypothyroidism, sickle cell disease, medium-chain acyl-CoA dehydrogenase deficiency [MCADD] and cystic fibrosis). Technologies such as mass spectrometry have revolutionised screening with the ability to analyse multiple biomarkers simultaneously from just a single blood spot. In 2011, in an effort to improve the health of newborns, six laboratories began a pilot to explore the potential of this technology in expanding the range of conditions screened to include five more metabolic disorders. Dr Fiona Carragher, Director of Biochemical Sciences at St Thomas’ Hospital, said: “For this expansion to be viable an effective treatment for each of the conditions screened must be available and there must be a window of clinical opportunity. It should require no additional blood to be taken and no extra laboratory equipment.” The pilot study screened for five additional disorders from the existing blood spot sample (ie maple syrup urine disease, homocystinuria, glutaric aciduria type I, isovaleric acidaemia, and long-chain acyl-CoA dehydrogenase deficiency). Individually these are rare but as a group are likely to affect one child in 30,000. “We already have the technology for these tests,” added Dr Carragher. “Using a multiplex approach, different analytes can be tested from a single 3-mm blood spot punch, and in just a few minutes. By adding these five new tests, we now have the capability of detecting many more conditions for no additional analytical time, all from the original blood sample.” This expanded screening has already yielded benefits; for example, in July 2012,


Dr Fiona Carragher is Director of Biochemical Sciences at St Thomas’ Hospital, London. THE BIOMEDICAL SCIENTIST 729


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