Severe neuromuscular forms of glycogen storage disease type IV: Histological, clinical, biochemical, and molecular findings in a large French case series.

Glycogen storage disease type IV (GSD IV), also called Andersen disease, or amylopectinosis, is a highly heterogeneous autosomal recessive disorder caused by a glycogen branching enzyme (GBE, 1,4-alpha-glucan branching enzyme) deficiency secondary to pathogenic variants on GBE1 gene. The incidence is evaluated to 1:600 000 to 1:800 000 of live births. GBE deficiency leads to an excessive deposition of structurally abnormal, amylopectin-like glycogen in affected tissues (liver, skeletal muscle, heart, nervous system, etc.). Diagnosis is often guided by histological findings and confirmed by GBE activity deficiency and molecular studies. Severe neuromuscular forms of GSD IV are very rare and of disastrous prognosis. Identification and characterization of these forms are important for genetic counseling for further pregnancies. Here we describe clinical, histological, enzymatic, and molecular findings of 10 cases from 8 families, the largest case series reported so far, of severe neuromuscular forms of GSD IV along with a literature review. Main antenatal features are: fetal akinesia deformation sequence or arthrogryposis/joint contractures often associated with muscle atrophy, decreased fetal movement, cystic hygroma, and/or hydrops fetalis. If pregnancy is carried to term, the main clinical features observed at birth are severe hypotonia and/or muscle atrophy, with the need for mechanical ventilation, cardiomyopathy, retrognathism, and arthrogryposis. All our patients were stillborn or died within 1 month of life. In addition, we identified five novel GBE1 variants.

Avoiding falsely low creatinine concentrations measured in patients treated with N-acetylcysteine for acetaminophen intoxication using enzymo-amperometric method - An in vitro and in vivo study.

BACKGROUND: Circulating creatinine is a biomarker of paramount importance in clinical practice. In cases of acetaminophen (APAP) intoxication, the antidote, N-acetylcysteine (NAC), interferes with commonly used creatininase-peroxidase methods. This study aimed to assess whether creatininase-amperometric methods were affected in this context. METHODS: This study includes in vitro interference tests, involving four creatinine assays using NAC-spiked plasma pools and an in vivo retrospective study comparing creatininase-peroxidase and creatininase-amperometric measurements in patients presenting with NAC-treated APAP poisoning. RESULTS: Creatininase-peroxidase method was impacted by NAC interference in a clinically-significant manner at therapeutic NAC levels (basal value recovery of 80 % and 70 % for 500 and 1000 mg.L-1 of NAC, respectively), surpassing the desirable Reference Change Value (RCV%). Enzymo-amperometric methods were not impacted. Among patients, a mean bias of -45.2 ± 28.0 % was observed for the peroxidase detection method compared to the amperometric in those who received NAC prior plasma sampling and -2.7 ± 5.4 % in those who did not. CONCLUSIONS: Our findings indicate that enzymo-amperometric creatinine assays remain unaffected by NAC interference due to the absence of the peroxidase step in the analytical process. Therefore, these methods are suitable to prevent spurious hypocreatininemia in APAP intoxicated patients undergoing NAC therapy.

Sex hormone binding globulin: The importance of establishing sex-based reference values.

OBJECTIVES: Assay of sex hormone binding globulin (SHBG), the main carrier protein for sexual steroids, is prescribed mainly by endocrinologists and performed in specialized laboratories. This study aimed to evaluate the analytic performance of an automated immunochemiluminescent assay (ImmunoDiagnostic Systems (IDS), Boldon, United Kingdom) compared to a manual radioimmunoassay (Cisbio Bioassays, Codolet, France). It further aimed to assess the suitability of the reference values proposed by IDS. MATERIALS AND METHODS: One hundred and forty sera were used to assess the analytic performance of the IDS kit. The coefficients of variation (CV%) for within- and between-run precision were calculated. The reference values provided by IDS were recalculated based on the regression curve equation obtained by comparing the IDS and Cisbio values on Passing-Bablok regression. The new sex-based reference values were then established and their concordance with clinical status was evaluated on Kappa coefficient. RESULTS: The new kit correlated strongly with the reference technique (R2=0.96). Based on the regression line equation, the new reference values for IDS were [20.9-50.6] nmol/L for men and [33.8-71.1] nmol/L for women. Agreement with the reference values we established was 0.933 for men and 0.825 for women, compared with 0.606 and 0.286 for the supplier's values. CONCLUSION: The performance of the IDS kit met the current recommendations and correlated strongly with the Cisbio method. The calculation of new sex-based reference values was needed to correctly classify patients according to androgen status, underlining the importance of systematically checking the reference values provided by suppliers.