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Congenital disorders of glycosylation (CDG) are a family of rare inherited metabolic disorders. This study aimed to examine the carbohydrate-deficient transferrin (CDT) screening results of 1,328 patients with suspected CDG by using transferrin- high pressure liquid chromatography (Tf- HPLC) method and to evaluate the performance of the method as a reference diagnostic tool.Relative CDT levels (CDT concentrations expressed as percent of total transferrin) were determined in serum samples by HPLC. The method sensitivity, specificity and positive predictive value (PPV) were further calculated.Abnormal transferrin isoform profile consistent with CDG Type-I and CDG Type-II were determined in 50 cases; in 44 cases asiolo-Tf (7.63 ± 5.44 %) and disialo-Tf (36.29 ± 9.04 %), in six cases monosialo-Tf (3.95 ± 0.95 %) and trisialo-Tf (25.05 ± 4.46 %) were determined and decreased tetrasialo-Tf (49.75 ± 11.59 %) was identified in all cases. Two cases having abnormal CDT pattern were molecularly diagnosed with hereditary fructose intolerance and galactosemia and 11 cases diagnosed with CDG based on clinical and molecular analysis showed a normal pattern. The sensitivity, specificity and positive predictive values of Tf-HPLC method were 81.96 %, 99% and 96 %, respectively.Tf-HPLC is a useful, highly sensitive, cost-advantageous and reliable method for the detection and preliminary diagnosis of CDG for laboratories working with large sample series. [ABSTRACT FROM AUTHOR]

Amplification-based ONT sequencing using two primer pools and long PCR results in fast, cheap and accurate screening of BTD gene. [Display omitted] • Molecular screening of biotinidase deficiency is critical for differential diagnosis. • BTD gene can be sequenced by Oxford Nanopore Technologies (ONT) using two primer pools. • ONT-based sequencing of BTD is rapid, effortless and cheap compared to second-generation sequencing systems. Biotinidase deficiency (BTD) is an autosomal recessive disorder characterized by impaired recycling of the water-soluble vitamin biotin which leads to a spectrum of clinical manifestations ranging from mild to severe, including mainly neurological and cutaneous symptoms. Biotin supplementation is a cornerstone of treatment, but diagnosis often relies on measuring serum enzyme activity, which needs to be confirmed by genetic analysis. Thus, molecular methods become necessary in the differential diagnosis of BTD. Accordingly, countries with a high-incidence have implemented next-generation sequencing (NGS) techniques to newborn screening programs for BT. Nevertheless, NGS platforms, while well-established, present challenges in cost, labor, accessibility, and duration for newborn screening programs targeting BTD, therefore these limitations necessitate the exploration of alternative systems to ensure efficient and widespread screening. Here, third-generation sequencing platforms, notably Oxford Nanopore Technology (ONT), present promising solutions to the associated challenges. Hence, in the present study, we aimed to develop an ONT-based assay for the screening of BTD gene. After designing and optimizing primers for long-PCR using reference DNA, we assessed the performance of the ONT assay in BTD patients previously diagnosed by enzyme assay and confirmed using Illumina-based sequencing. The results demonstrate a strong correlation between the two methods, indicating the reliability of the ONT-based assay. Moreover, this first in-house single gene testing specifically tailored for BTD successfully detected previously known genetic variants with high sequencing depths, affirming the effectiveness of ONT-based sequencing in human genetics. [ABSTRACT FROM AUTHOR]