An audit of newborn screening procedure: impact on infants presenting clinically before results are available.

BACKGROUND AND OBJECTIVE: Tandem mass spectrometry-based newborn screening (NBS) is a powerful screening tool. The NBS process includes sample collection, shipment, testing, analysis, reporting and communication with the infant's family. We explored the NBS programme-related factors that may delay diagnosis and may influence timely initiation of treatment in neonates who present before the screening results are available and therefore urgently need diagnosis and treatment. STUDY DESIGN: Detailed retrospective review of all data regarding sampling, shipment, testing and notification, contact with family and initiation of treatment of all neonates with disorders of fatty acid oxidation (FAO) and protein metabolism (PM), who presented clinically before NBS results were available, between 1-February-2002 and 31-January-2014. RESULTS: Of 847,418 newborns screened, 18 infants presented clinically before NBS results were available (FAO n = 9, median age 2.5 days; PM n = 9, median age 3 days). Samples were collected from 11 infants at age 48-72 h, as per instructions, and were received in the laboratory at a median age of 7 days (median 4 days from sample collection until receipt in the laboratory). Results were available within 24h in 16/18 infants. Treatment for a suspected metabolic disorder was initiated in seven infants before results were available. CONCLUSIONS: An audit of the programme procedures enabled the identification of issues that can be improved. Some patients benefited from the availability of results shortly after presentation. Good communication between the laboratory, the clinical metabolic specialist service and the primary treating team ensures timely initiation of treatment in these infants.

4-hydroxyglutamate is a biomarker for primary hyperoxaluria type 3.

Primary hyperoxaluria type 3 (PH3) is a recently identified inborn error of 4-hydroxyproline metabolism causing kidney stone disease. Diagnosis to date has relied on mutation detection. The excretion of 4-hydroxyglutamate (4OHGlu) was investigated in controls and a cohort of nine patients with PH3 and their parents using flow injection tandem mass spectrometry. 4OHGlu was stable in acidified urine samples and was not influenced by diet. Its measurement was readily incorporated into an existing multi-analyte panel for comprehensive screening for inborn errors of metabolism. There was a steady decline with age in 4OHGlu levels, expressed as µmol/mmol of creatinine, in controls. Levels in patients with PH3 ranged from 6.5 to 98 µmol/mmol of creatinine and were all significantly increased when compared to age-matched controls (<4.2). Levels in eight parents (obligatory carriers of the corresponding mutation) were moderately, but significantly increased, ranging from 0.6 to 2.5 (age-matched controls <1.4, p = 0.03). Urine 4OHGlu screening was used to prospectively diagnose PH3 in an 18-month-old boy with calcium oxalate kidney stone disease associated with hyperoxaluria. 4OHGlu was also increased in a stored newborn screening dried blood spot sample from this child (37 µmol/L, controls <2.53). 4OHGlu testing provides a robust and high-throughput biochemical screen for PH3.