We conclude that perfusion studies with patient blood are of added value in the diagnostic process, which resulted in identification of a novel molecular defect in the P2Y(12) gene of a patient with haemorrhagic diathesis.

Maple syrup urine disease (MSUD) leads to severe neurological deterioration unless diagnosed early and treated immediately. We have evaluated the effectiveness of 11 years of MSUD newborn screening (NBS) in the Netherlands (screening >72 hours, referral if both total leucine (Xle) and valine ≥400 μmol/L blood) and have explored possibilities for improvement by combining our data with a systematic literature review and data from Collaborative Laboratory Integrated Reports (CLIR). Dutch MSUD NBS characteristics and accuracy were determined. The hypothetical referral numbers in the Dutch population of additional screening markers suggested by CLIR were calculated. In a systematic review, articles reporting NBS leucine concentrations of confirmed patients were included. Our data showed that NBS of 1 963 465 newborns identified 4 MSUD patients and led to 118 false‐positive referrals (PPV 3.28%; incidence 1:491 000 newborns). In literature, leucine is the preferred NBS parameter. Total leucine (Xle) concentrations (mass‐spectrometry) of 53 detected and 8 false‐negative patients (sampling age within 25 hours in 3 patients) reported in literature ranged from 288 to 3376 (median 900) and 42 to 325 (median 209) μmol/L blood respectively. CLIR showed increasing Xle concentrations with sampling age and early NBS sampling and milder variant MSUD phenotypes with (nearly) normal biochemical profiles are causes of false‐negative NBS results. We evaluated the effect of additional screening markers and established the Xle/phenylalanine ratio as a promising additional marker ratio for increasing the PPV, while maintaining high sensitivity in the Dutch MSUD NBS.

Background Newborn screening (NBS) for classic congenital adrenal hyperplasia (CAH) consists of 17-hydroxyprogesterone (17-OHP) measurement with gestational age-adjusted cut-off values. A second heel puncture (HP) is performed in newborns with inconclusive results to reduce false-positives. We assessed the accuracy and turnaround time of the current CAH NBS-algorithm and compared this to alternative algorithms by performing a second-tier 21-deoxycortisol (21-DF) pilot-study. Methods Dried blood spots (DBS) of newborns with inconclusive and positive 17-OHP (immunoassay) first HP results were sent from regional NBS laboratories to the Amsterdam UMC Endocrine Laboratory. In 2017–2019 21-DF concentrations were analyzed by liquid chromatography-tandem mass spectrometry, in parallel with routine NBS. Diagnoses were confirmed by mutation analysis. Results 328 DBS were analyzed. 37 newborns had confirmed classic CAH, 33 were false-positive and 258 were categorized as negative in the second HP following the current algorithm. In the second-tier, all 37 confirmed CAH had elevated 21-DF concentrations, all 33 false-positives and 253/258 second HP negatives had undetectable 21-DF concentrations. The elevated 21-DF of the other five newborns may be NBS false-negatives or second-tier false-positives. Adding the second-tier to inconclusive first HPs reduced the number of false-positives to 11 and prevented all 286 second HPs. Adding the second-tier to both positive and inconclusive first HPs eliminated all false-positives at the cost of delayed referral for 31 CAH patients (1–4 days). Conclusion Application of the second-tier 21-DF measurement to inconclusive first HPs improved our CAH NBS by reducing false-positives, abolishing the second HP and thereby shortening referral time

Spinal muscular atrophy (SMA) is one of the leading genetic causes of infant mortality with an incidence of 1:10,000. The recently-introduced antisense oligonucleotide treatment improves the outcome of this disease, in particular when applied at an early stage of progression. The genetic cause of SMA is, in >95% of cases, a homozygous deletion of the survival motor neuron 1 (SMN1) gene, which makes the low-cost detection of SMA cases as part of newborn screening programs feasible. We developed and validated a new SALSA MC002 melting curve assay that detects the absence of the SMN1 exon 7 DNA sequence without detecting asymptomatic carriers and reliably discriminates SMN1 from its genetic homolog SMN2 using crude extracts from newborn screening cards. Melting curve analysis shows peaks specific for both the SMN1 gene and the disease modifying SMN2 homolog. The detection of the SMN2 homolog, of which the only clinically relevant difference from the SMN1 gene is a single nucleotide in exon 7, was only used to confirm a correct reaction in samples that lacked the SMN1 gene, and not for SMN2 quantification. We retrieved 47 DBS samples from children with genetically-confirmed SMA, after informed consent from parents, and 375 controls from the national archive of the Dutch National Institute for Public Health and the Environment (RIVM). The assay correctly identified all anonymized and randomized SMA and control samples (i.e., sensitivity and specificity of 100%), without the detection of carriers, on the three most commonly-used PCR platforms with melting curve analysis. This test's concordance with the second-tier 'golden standard' P021 SMA MLPA test was 100%. Using the new P021-B1 version, crude extracts from DBS cards could also be used to determine the SMN2 copy number of SMA patients with a high level of accuracy. The MC002 test showed the feasibility and accuracy of SMA screening in a neonatal screening program.

Fetal lung maturity tests that are performed in vaginally obtained specimens in patients with ruptured membranes are of no use in the prediction of RDS.