Cu/Zn superoxide dismutase quantification from fetal erythrocytes—an efficient confirmatory test for Down's syndrome after maternal serum screening and sonographic investigations

Abstract

An enzyme immunoassay especially designed for the quantification of Cu/Zn superoxide dismutase (SOD) in erythrocytes has been applied to measure the SOD of outcomes with high risk for Down's syndrome. From 148 fetuses SOD was quantified from erythrocytes of umbilical vein blood and related to the number of cells, the content of haemoglobin (Hb), and to the haematocrit (Hc). Comparative studies between the SOD content of erythrocytes from the fetuses and their mothers resulted in similar SOD levels (14.09 +/- 1.20 for fetal and 14.48 +/- 1.63 for maternal cells) with a 1.84-fold smaller variance for fetal cells. The best differentiation between normal fetuses and fetuses with Down's syndrome resulted from the SOD/cell ratio followed by the SOD/Hb ratio. Fixing a cut-off value from the probability density functions that the method results in a specificity of 99.99 per cent, the sensitivity to detect cases of Down's syndrome was 99.71 per cent for the SOD/cell ratio, 70.92 per cent for the SOD/Hb ratio, and 60.21 per cent for the SOD/He ratio. Nine cases with Down's syndrome were correctly diagnosed by the SOD/cell ratio determination. Eight of these were confirmed as free trisomy 21 by karyotype analysis and one was found to be a triploidy. The latter was not detected by the SOD/Hb and SOD/Hc ratios because of the one-third higher content of haemoglobin and the larger volume of the erythrocytes which resulted in ratios within the normal range.

Thymic–thoracic ratio in fetuses with trisomy 21, 18 or 13

“…In addition to the diminished numbers of T‐cells, the function of thymocyte subpopulations is reduced24; this was also confirmed in fetal blood sampled at midgestation13, 19. In trisomy 21 fetuses, other possible mechanisms of immune deficiency may be caused by overproduction of the enzyme copper‐zinc superoxide dismutase (SOD)25 whose gene is located on chromosome 21q22.1. The resulting decrease in zinc concentration, the reduced bioavailability of thymulin and the suppressed cellular production of prostaglandins E2 and D2 could be the pathogenic mechanism of the immune deficiency26.…”

Mental Retardation: Genetic Findings, Clinical Implications and Research Agenda

“…It provides a rapid method of karyotyping but at present its rather low sensitivity makes it appropriate only for low-risk screening (Evans et al, 1994). However, specificity of detection of foetal cells is improving (Bianchi et al, 1993) and both biochemical and molecular techniques can be used to detect abnormalities (Porstmann et al, 1991). Second, there is the biopsy of foetal cells at the primitive blastocyte stage, using eggs flushed out of the uterus (Edwards, 1993;Verlinsky & Kuliev, 1993).…”

Curvas padrão pôndero-estatural de portadores de Síndrome de Down procedentes da região urbana da cidade de São Paulo

“…A correlação genótipo/fenótipo foi facilitada pela identificação de genes em regiões deste cromossomo envolvidos na expressão do comprometimento intelectual, do risco de cardiopatias congênitas, leucemias e outras doenças (KOREMBERG, 1991;DAHAMANE et al, 1995;BROMAN et al, 1998 (DARNULE et al, 1990;KRONQUIST et al, 1990;PORSTMANN et al, 1991;KNIGHT, 1992;KELLY et al, 1994;BOUÉ & MULLER, 1995;OURY, 1995;WALD, 1988WALD, e 1996. …”