Secondary non-invasive prenatal screening for fetal trisomy: an effectiveness study in a public health setting.

OBJECTIVE: To evaluate the effectiveness of secondary screening using non-invasive prenatal testing (NIPT) in a routine NHS setting including test performance, turn-around times (TATs) and no-call (failure to obtain result) rates. To examine the influence of maternal and fetal characteristics on test performance. DESIGN: Retrospective cohort. SETTING: London teaching hospital. SAMPLE: A total of 8651 pregnancies undergoing screening for fetal trisomy using NIPT provided by an NHS cell-free DNA screening laboratory - the SAFE laboratory. METHODS: Screening test evaluation and TATs. Univariate and multivariate logistic regression analysis to identify significant predictors of no-call results and reported by low fetal fraction (<2%), very high fetal fraction (>40%) and processing failure. MAIN OUTCOME MEASURES: Test performance, TATs and no-call rates, factors affecting no-call results. RESULTS: Average TAT was 4.0 days (95% CI 4.0-4.2 days). Test sensitivities for trisomies 21 and 13/18 were 98.9% (95% CI 95.9-99.9%) and 90.4% (95% CI 80.0-96.8%), respectively. The overall no-call rate was 32/8651 (0.37%, 95% CI 0.26-0.52%). The overall risk of a no-call result was influenced by gestational age, dichorionic twin pregnancy, history of malignancy and pregnancies affected by trisomy 13/18, but not by maternal weight or use of low-molecular-weight heparin. CONCLUSIONS: High-throughput NIPT can be effectively embedded into a public health NHS setting. TATs of 4 days and no-calls of <0.5% were well within clinically desirable tolerances. Gestational age, maternal weight, assisted reproductive techniques, use of low-molecular-weight heparin and past history of malignancy did not have major impacts on test no-call rates and should not constitute reasons for withholding the option of NIPT from women. TWEETABLE ABSTRACT: Turn-around times of 4 days, no-call (test failure) rates of 0.37% and highly accurate NIPT can be successfully embedded in the NHS.

IgG4 in human colostrum and human milk: continued local production or selective transport from serum.

Colostrum, mature milk, and paired plasma samples were obtained from 10 postpartum women who had not been previously studied. The geometric mean concentration of IgG4 in colostrum (3.3 micrograms/ml) was similar to the mean concentration in mature milk (3.0 micrograms/ml). The arithmetic mean for the percent of IgG = IgG4 was 10.3 +/- 3.3% for colostrum, 10.3 +/- 3.1% for mature milk, 2.6 +/- 0.3% for early plasma, and 1.7 +/- 0.3% for later plasma. Local mammary production of immunoglobulin was determined by subtracting the estimated serum contribution from the measured concentration in colostrum or milk. Evidence for local mammary production of IgG4 was found in 5 of 10 colostrum samples and 8 of 10 mature milk samples. These observations indicate that the previously observed selective enrichment of IgG4 in colostrum is also true for mature milk. These are the first studies suggesting continued local production of any immunoglobulin other than IgA in mature human breast milk.

A reliable cross-circulation model: its use in studying humoral agents.

The purpose of this study was to develop an expeditious and reliable system to examine early alterations in proliferating liver tissue in vivo, uncomplicated by the haemodynamic changes associated with partial hepatectomy. We describe an improved, dependable, massive blood-exchange system, involving aortic blood transposition between two rats, which meets these criteria. The use of heparinized, silicone-rubber tubing and postoperative recirculation obviate the need for supplemental anticoagulants and minimizes haemorrhage. The procedure is rapid, and survival is > 95% for up to 48 h. We cite both the advantages of using this model generally to study humoral agents, and specific advantages associated with studies relating to a humoral hepatic mitogen. As an example in this regard, we present results obtained using this system to examine chromatin protein methylation in the intact liver of rats coupled to partially hepatectomized partners. Labelling with a mixture of 3H-methyl-L-methionine and 2-14C-DL-methionine, we demonstrate an enhancement of methylation in crude chromatin protein fractions obtained from intact liver tissue responding to humoral agents provided by blood exchanged from partially hepatectomized rats. This substituent enhancement appears to correlate with the degree of stimulation of DNA replication in this organ.

Amino acids and control of nucleolar size, the activity of RNA polymerase I, and DNA synthesis in liver.

The volume of nucleolar material per nucleus and the activity of RNA polymerase I (RNA nucleotidyltransferase I) become doubled in the liver cells of rats that are fed for several days a diet that lacks essential amino acids. Omission of methionine from a fully supplemented diet is equivalent to leaving out all the amino acids, and the responses to a deficiency of tryptophan are about 40% as great. Deprivation of one of the remaining essential amino acids gives either small responses or none at all. Supplementation of the methionine-free diet with cystine blocks the nucleolar enlargement and the enhancement of the polymerase activity that would otherwise take place, but the dispensable amino acid does not affect the responses to a deprivation of one of the other essential amino acids. After deprivation of all the essential amino acids or only methionine, hepatocytes make DNA when the rat is fed a meal with protein. A preparatory diet lacking in tryptophan is much less effective; a deficiency in any of the other indispensable compounds tested fails to prepare the liver for DNA synthesis. The results give hope that elucidation of the means by which methionine deprivation affects the nucleolus will also provide information on the regulation of nuclear DNA replication in liver. One attractive possibility is that the amino acid deficiency acts by producing some imbalance in protein metabolism.