The diagnostic challenge of mild citrulline elevation at newborn screening.

Citrulline is a target analyte measured at expanded newborn screening (NBS) and its elevation represents a biomarker for distal urea cycle disorders and citrin deficiency. Altered ratios of citrulline with other urea cycle-related amino acids are helpful for the differential diagnosis. However, the use of cut-off values in screening programmes has raised the issue about the interpretation of mild elevation of citrulline levels detected at NBS, below the usual range observed in the "classical/severe" forms of distal urea cycle disorders and in citrin deficiency. Herein, we report ten subjects with positive NBS for a mild elevation of citrulline (<100 µmol/L), in whom molecular investigations revealed carriers status for argininosuccinate synthase deficiency, a milder form of argininosuccinate lyase deficiency and two other diseases, lysinuric protein intolerance and dihydrolipoamide dehydrogenase deficiency, not primarily affecting the urea cycle. To guide the diagnostic process, we have designed an algorithm for mild citrulline elevation (<100 µmol/L) at NBS, which expands the list of disorders to be included in the differential diagnosis.

Multiple office blood pressure measurement: a novel approach to overcome the weak cornerstone of blood pressure measurement in children. Data from the SPA project.

BACKGROUND: This contribution aims to report and analyze a novel approach for office blood pressure measurement in children. METHODS: Healthy children 5 to 8 years of age were eligible. After 5 minutes rest, 10 unattended blood pressure readings were taken at 3-minute intervals using a validated automated oscillometric device. After discarding outlier values (< 5th or > 95th percentile of the recorded values), the coefficient of variation and the mean of the 10 readings were calculated. The single readings #1 to #10 were compared with this elaborated average of the 10 measurements. RESULTS: Two hundred eighty-one healthy, non-obese children (137 females, 49%), median age 5.7 (IQR 5.3-6.1) years, were analyzed. The median coefficients of variation were 7% (IQR 5-9) for systolic and 4% (IQR 3-6) for diastolic blood pressure. The first 3 measurements were significantly different from the average, while the readings #4 to #10 were not. Based on the average, only nine subjects had a systolic or diastolic blood pressure > 90th centile (n = 3 > 95th percentile). CONCLUSIONS: Although most guidelines advise three blood pressure readings, these findings suggest that in children, office blood pressure measurement might be improved by including ten measurements. In situations of time constraints, the fourth blood pressure reading might be used as a reliable approximation.

High Incidence of Partial Biotinidase Deficiency in the First 3 Years of a Regional Newborn Screening Program in Italy.

Biotinidase deficiency (BD) is an autosomal recessive inherited disorder in which the enzyme biotinidase is totally or partially defective and the vitamin biotin is not recycled. BD meets the major criteria for a population screening program. Newborn bloodspot screening (NBS) allows early diagnosis of BD, thus preventing the high morbidity and mortality associated with untreated disease. Both profound and partial BD variant can be detected by NBS test, and serum enzyme activity and/or mutational analysis are required for definitive diagnosis. In Italy, BD is included in the screening panel for inborn errors of metabolism (IEMs) that has been declared mandatory in 2016. We analyzed the data of the first 3 years of the NBS for BD in our region (Abruzzo, Italy), with the aim to describe the outcomes of this recently introduced screening program. In over 26,393 newborns screened, we found 2 carriers and 16 cases with genotype associated with partial BD. Since the serum biotinidase assay has been recently introduced in our algorithm, only three of our newborns met the criteria of genetic and biochemical confirmation, with an incidence of 1:8797, which is in the high range of what has been reported in the literature. All affected infants carried the 1330G>C (D444H) variant in compound heterozygosis, with variants known to be associated with profound BD. A variant previously not described and likely pathogenic was found in one newborn. None of the infants had signs or symptoms. The study of the distribution of the enzyme activity in our population allowed us to validate the adopted cutoff with which the program has a positive predictive value of 18% and to analyze some preanalytical factors influencing biotinidase activity: A correlation of the enzyme activity with gestational age and time at specimen collection was found. Lower mean values of enzyme activity were found in infants born in the summer.

Fluid intake and blood pressure in children: the Salus per Aquam project.

BACKGROUND: Sodium intake is known to contribute to the development of hypertension, thus intake reduction is a cornerstone in the prevention and management of hypertension. The increase in renal sodium excretion might represent a further potential preventive and/or therapeutic opportunity. OBJECTIVE: To explore the working hypothesis that an increased fluid intake can improve renal sodium handling towards a decrease in blood pressure. METHODS: The SPA Project is a multicenter, observational, cross-sectional, cohort study investigating healthy children, aged 5-8 years as to sodium and fluid intake by means of urinary sodium and creatinine from multiple samples taken in different days in order to characterize them in lower/higher sodium and lower/higher fluid intake. Both SBP and DBP (by multiple office blood pressure measurements) were used as outcome measures. RESULTS: Three hundred and thirty-nine healthy, nonoverweight children (51.6% boys) with a median age of 5.7 years old (IQR: 5.3-6.2) participated in the study but only 223 could be analyzed. Among children with higher sodium intake, those introducing more fluids, showed a significantly lower blood pressure (both systolic and diastolic) compared with those with lower fluid intake: systolic 86.0 ±â€Š8.5 vs. 90.0 ±â€Š8.1 mmHg; P = 0.014 and diastolic: 53.8 ±â€Š4.9 vs. 58.6 ±â€Š6.6 mmHg; P < 0.0001. CONCLUSION: An increased fluid intake is associated with a reduced blood pressure possibly by increasing renal sodium excretion. We speculate that this simple, highly acceptable, inexpensive, and harmless measure might have a role in preventing and/or minimizing the epidemics of hypertension and of its related morbidities both in children and in adults.

Partial Biotinidase Deficiency Revealed Imbalances in Acylcarnitines Profile at Tandem Mass Spectrometry Newborn Screening.

Biotinidase (BTD) deficiency is an autosomal recessive inherited neurocutaneous disorder. BTD recycles the vitamin biotin, a coenzyme essential for the function of four biotin-dependent carboxylases, including propionyl-CoA carboxylase, 3-methylcrotonyl-CoA carboxylase, pyruvate carboxylase, and acetyl-CoA carboxylase. Due to deficient activities of the carboxylases, BTD deficiency is also recognized as late-onset multiple carboxylase deficiency and is associated with secondary alterations in the metabolism of amino acids, carbohydrates, and fatty acids. BTD deficiency can be classified as "profound", with less than 10% of mean normal activity, and as "partial" with 10-30% of mean normal activity. Newborn screening (NBS) of BTD deficiency is performed in most countries and is able to detect both variants. Moreover, mild metabolic alterations related to carboxylase deficiency in profound BTD deficiency could result and possibly be revealed in the metabolic profile by tandem mass spectrometry (MS/MS) NBS. Here, we report the case of a newborn female infant with an initial suspected BTD deficiency at the NBS test, finally confirmed as a partial variant by molecular testing. Although BTD deficiency was partial, interestingly her metabolic profile at birth and during the follow-up tests revealed, for the first time, alterations in specific acylcarnitines as a possible result of the deficient activity of biotin-dependent carboxylases.

A Case of Suspected Hyperphenylalaninemia at Newborn Screening by Tandem Mass Spectrometry during Total Parenteral Nutrition.

Phenylketonuria (PKU) is a rare autosomal recessive condition affecting about 1 in 10,000 people in the Europe, with a higher rate in some countries, like Ireland and Italy. In Italy, newborn screening (NBS) by MS/MS allows the diagnostic suspicion of PKU and its variants (Hyperphenylalaninemia (HPA), Tetrahydrobiopterin (BH4) synthesis deficiency, and Tetrahydrobiopterin (BH4) recycling deficiency) through the quantification of Phenylalanine (Phe) and the Phenylalanine/Tyrosine (Phe/Tyr) ratio in dried blood Spot (DBS) samples. Here, we report a case of an HPA whose suspicion was possible with expanded NBS, even if the normal-weight newborn was in total parenteral nutrition (TPN). It is known that TPN may present metabolic alterations, mainly for amino acids at NBS in MS/MS, frequently causing false positives. Actually, TPN is considered a special protocol in NBS, requiring several sample collections. In particular, a DBS sample is required before TPN, at basal time point (48 h after birth) and 72 h after the end of the procedure. In the case we report, even if the first DBS sample (before TPN) resulted negative, the repeated NBS tests revealed increased levels of Phe and dramatically high Phe/Tyr ratio. Thus, the newborn was recalled, and the NBS test was repeated several times before that HPA suspicion was confirmed by other specific biochemical tests. This case highlights the importance of Phe/Tyr ratio, only detectable by MS/MS analysis, in supporting the diagnostic suspicion during amino acids administration in the neonatal period.