Objective-To determine the relation between maternal serum cx fetoprotein and free 1 human chorionic gonadotrophin concentrations in pregnancies complicated by trisomy 18
IntroductionBiochemical screening for trisomy 21 can now identify 65-75% of cases early in the second trimester, particularly when combinations of a fetoprotein and free 1 human chorionic gonadotrophin concentrations are used as markers. 1-6The prospect of first trimester screening with these analytes to achieve detection rates exceeding 50% seems a definite possibility.7-9 The impetus for all this development was the finding by one of us of a low matemal serum ot fetoprotein concentration in a case of trisomy 18.10Trisomy 18 is the second most frequent autosomal trisomy (after trisomy 21) and has a birth incidence of
A commercially available substrate-labelled fluorescent immunoassay procedure has been modified to create a simple rapid method for the determination of capillary phenytoin concentration in dried filter paper blood spots of patients on phenytoin therapy. The specimens are collected and dispatched to the laboratory by the patient, thus domiciliary monitoring of phenytoin therapy can take place. The technique was validated by comparing the phenytoin results of simultaneously collected capillary dried blood spots and conventional plasma samples. The technique offers a convenient method for overcoming many of the practical problems of monitoring phenytoin therapy in epilepsy.
SUMMARY. We report a multicentre clinical field trial of a novel dual analyte enzyme immunoassay method for the simultaneous measurement of alpha-fetoprotein (AFP) and free (j-human choriogonadotropin (hCG) in the same micro titre well. The assay was shown to have good technical performance in the hands of all trial centres, with between assay coefficients of variation better than 10% for both analytes across the whole of the assay ranges. The method compared well with single analyte measuring procedures and produced acceptable performance as judged by external quality assurance criteria. Recovery of added analyte and analyte dilution curves also showed acceptable performance.In clinical evaluation of a large set of neural tube defect cases, good clinical discrimination from unaffected cases was observed using AFP. With over 150 Down's syndrome cases, the combination of AFP and free (3 hCG confirmed the high detection rates achievable using this marker combination, with detection rates in excess of 70% in early gestation.We conclude that the combination of clinically superior markers coupled with technologically innovative assay design will lead to more efficient Down's screening programmes.
Additional key phrases: alpha-fetoprotein; free beta-human choriogonadotropinIn many parts of the developed world, second trimester screening for neural tube defects using the biochemical marker maternal serum crfetoprotein (AFP) has been a routine part of obstetric practice since the publication of the UK Collaborative studies in the mid 1970s.1 The observation by one of US,2 that lowered levels of maternal serum AFP during the second trimester were associated with fetal chromosomal trisomies, added a further dimension to second trimester Correspondence: Mr K Spencer. 394 screening for birth defects. More recently, the use of new biochemical markers has been shown to improve screening efficiency, such that with the markers AFP and free (j-human choriogonadotropin (hCG) it is now possible to achieve detection rates of the order of 75-80010 as demonstrated in retrospective':" or prospective? studies. The recent observation that maternal serum free (j-hCG is also elevated in the first trimester of pregnancies affected by Down's syndrome and lowered in pregnancies affected by trisomy 18, provides further evidence of the value of this biochemical marker. 8
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