Glucose-6-phosphate isomerase deficiency-Nahariya: extreme in vitro and in vivo lability of the mutant enzyme

A glucose-6-phosphate isomerase deficiency is described in an Arab boy suffering from chronic hemolytic anemia. The patient was probably true homozygous for the defect. The residual enzyme activity in his red blood cells (RBC) was approximately 30% of normal. The most striking enzyme abnormality observed was an extreme heat lability: upon incubation at 45 C, greater than 90% of activity was lost within 15 min. Furthermore, an increased affinity for the substrate glucose-6-phosphate was shown. The lability of the enzyme was also shown to exist in vivo by separating the patient's RBC into four fractions of different cell age by centrifugation on a discontinuous density gradient. This in vivo lability of the enzyme is believed to be the main cause of the hemolytic diathesis. Remarkably, the residual activity of the enzyme in the RBC of obligate heterozygotes was comparable to that in the patient. However, their enzyme activity was only slightly more labile than that in normal RBC and consequently no signs of hemolysis were noticed

Automated reticulocyte parameters for hereditary spherocytosis screening

The laboratory diagnosis of hereditary spherocytosis (HS) is based on several screening and confirmatory tests; our algorithm includes clinical features, red blood cell morphology analysis and cryohaemolysis test, and, in case of positive screening, sodium dodecyl sulphate polyacrylamide gel electrophoresis as a diagnostic test. Using the UniCel DxH800 (Beckman Coulter) haematology analyser, we investigated automated reticulocyte parameters as HS screening tool, i.e. mean reticulocyte volume (MRV), immature reticulocyte fraction (IRF) and mean sphered cell volume (MSCV). A total of 410 samples were screened. Gel electrophoresis was applied to 159 samples that were positive for the screening tests. A total of 48 patients were diagnosed as HS, and seven were diagnosed as acquired autoimmune haemolytic anaemia (AIHA). Some other 31 anaemic conditions were also studied. From the receiver operating characteristic (ROC) curve analysis, both delta (mean cell volume (MCV)-MSCV) and MRV presented an area under the curve (AUC) of 0.98. At the diagnostic cut-off of 100 % sensitivity, MRV showed the best specificity of 88 % and a positive likelihood ratio of 8.7. The parameters IRF, MRV and MSCV discriminated HS not only from controls and other tested pathologies but also from AIHA contrary to the cryohaemolysis test. In conclusion, automated reticulocyte parameters might be helpful for haemolytic anaemia diagnostic orientation even for general laboratories. In combination with cryohaemolysis, they ensure an effective and time-saving screening for HS for more specialised laboratories.JOURNAL ARTICLESCOPUS: ar.jinfo:eu-repo/semantics/publishe