Search PubMed⌕ Search

Biomedical subjects

K Spencer

Publications and source records attributed to K Spencer.

At least 127 records · Page 7Linked to original sources
PubMed1993

Free beta-chorionic gonadotropin: a cross-reactivity study of two immunometric assays used in prenatal maternal serum screening for Down's syndrome.

We have evaluated the cross-reactivity characteristics of two distinct immunometric assays for the measurement of free beta-human chorionic gonadotropin (free beta). These maternal serum assays have been used in the initial studies which evaluated free beta as a marker in the prenatal detection of Down's syndrome. It has been suggested that free beta assays are subject to substantial potential for cross-reactivity. To confirm that free beta was the analyte responsible for enhanced detection efficiency both non-competitive and competitive cross-reactivity evaluations were undertaken. These studies demonstrated acceptably small cross-reactivity to other glycoprotein hormones or their beta components. We conclude that properly designed free beta assays will provide specific analyte measurement and improved detection efficiency in Down's syndrome screening.

Antibodies, Monoclonal↗
PubMed1993

Dual analyte immunoassay in neural tube defect and Down's syndrome screening: results of a multicentre clinical trial.

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 beta-human choriogonadotropin (hCG) in the same microtitre 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 analyte 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 beta 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.

Adolescent↗
PubMed1993

Stability of intact chorionic gonadotropin (hCG) in serum, liquid whole blood, and dried whole-blood filter-paper spots: impact on screening for Down syndrome by measurement of free beta-hCG subunit.

The use of multiple maternal serum biochemical markers in screening for Down syndrome is gaining worldwide acceptance. We sought to study the impact of the potential instability of intact human chorionic gonadotropin (hCG) on free beta-hCG subunit, a marker that has recently been used successfully in such screening. We found that, in practice, any changes in free beta-hCG due to the instability of intact hCG do not inhibit the effectiveness of free beta-hCG as a marker for Down syndrome. This was proven by controlled laboratory experiments at various stress temperatures, freeze-thaw studies, and analysis of a large set of screening data with particular reference to time in transit for individual samples. Data from controlled dissociation studies demonstrate that any apparent increase in free beta-hCG due to the instability of intact hCG cannot be attributed simply to the dissociation of intact hCG. Finally, for large-scale mass population screening in areas of the world where transport delays, safety concerns, and high temperatures preclude the shipment of liquid whole blood, dried whole-blood spots in filter paper provide a suitable delivery system with many advantages.

Blood Specimen Collection↗
PubMed1993

Screening for Down's syndrome. The role of intact hCG and free subunit measurement.

The role of intact, total, free alpha and free beta hCG in Down's syndrome screening is reviewed. I discuss the evidence for the enhanced detection of Down's syndrome in the second trimester using hCG beta and review the data with respect to first trimester screening with hCG subunits. I conclude that Down's syndrome screening using hCG is now well established and that increasing evidence from both retrospective and prospective studies now supports the improved detection achievable using assays that specifically measure hCG beta.

Adolescent↗
PubMed1992

Dual Analyte immunoassay--a new approach to neural tube defect and Down's syndrome screening.

A microtiter plate based Dual Analyte enzyme-immunoassay method for the simultaneous measurement of alpha-fetoprotein (AFP) and Free-beta human chorionic gonadotrophin (hCG) was evaluated. This rapid assay, which has application in both Neural Tube Defect screening and Down's screening, shows good precision with between assay coefficients of variation between 5 and 7.5% for AFP and 3.7 to 5.8% for Free-beta(hCG). Correlation with single analyte procedures is good, with correlation coefficients being greater than 0.91 in both cases. Clinical discrimination in detecting both types of abnormalities is not compromised by this new simultaneous Dual Analyte assay. We conclude that the Dual Analyte approach, which combines analytes achieving the highest known detection efficiency, will bring about improvements in the efficiency of screening, reduce costs and improve report turnaround, all leading to better quality of patient care.

Chorionic Gonadotropin↗
PubMed1992

Free beta human choriogonadotropin in Down's syndrome screening: a multicentre study of its role compared with other biochemical markers.

To ascertain the value of maternal serum free beta-human choriogonadotropin subunit measurement in Down's syndrome screening and to compare its effectiveness when screening with a variety of biochemical markers, we have evaluated maternal serum free beta-human choriogonadotropin, total human choriogonadotropin, alpha-fetoprotein and unconjugated oestriol in a large multicentre study of over 2800 unaffected cases and 90 affected cases, the largest collection of Down's cases ever reported. Of all the markers identified to date, free beta-human choriogonadotropin is the marker of choice for use in Down's syndrome screening. When used in early gestation (14-16 weeks) in combination with alpha-fetoprotein and maternal age, it will allow the detection of 77% of Down's cases. A side-by-side comparison with the performance of total human choriogonadotropin shows the superior detection efficiency of free beta-human choriogonadotropin. Unconjugated oestriol adds nothing further to the detection rate compared with the use of alpha-fetoprotein and free beta-human choriogonadotropin alone, and its use results in a 1% increase in false positive rate. We conclude that unconjugated oestriol has no value in Down's screening. The superior detection rate obtained using free beta-human choriogonadotropin is a result of superior detection of Down's cases in women under 30 years old, where the free beta-human choriogonadotropin combination detects 100% more cases than does the total human choriogonadotropin combination.

Biomarkers↗
PubMed1992

The Americans With Disabilities Act of 1990 expands employment opportunities for persons with developmental disabilities.

The primary purpose of the ADA is the full inclusion of persons with disabilities within their communities. The ADA prohibits discrimination on the basis of disability in the areas of employment, transportation, public accommodations, telecommunications, and state and local government agencies. The person described in this report encountered some of this discrimination. He successfully obtained paid community-integrated employment only after overcoming major obstacles and barriers, the greatest being transportation. In our highly mobile society, reliable transportation is essential for the acquisition and maintenance of community-integrated employment. The participant was repeatedly denied access to public transportation on the basis of his disability. To help overcome this barrier, Transition Services had to provide needed transportation at great expense, which delayed opportunities for the participant to gain control of this aspect of his life. Enactment of the ADA makes it more difficult for public transportation agencies to deny services to persons with disabilities by claiming inconvenience or lack of accessible vehicles. When publicly funded transportation programs assume their full responsibility for transportation to the public, agencies like Transition Services can focus on individualized employment and training issues rather than on providing transportation. In the workplace, the employer's willingness to work cooperatively with the participant and the staff of Transition Services resulted in several low-cost and reasonable accommodations based on the participant's needs and abilities. A simple rearrangement of work space allowed the participant to perform his job while benefiting the other workers in the crowded restaurant kitchen.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1991

Evaluation of an assay of the free beta-subunit of choriogonadotropin and its potential value in screening for Down's syndrome.

In this study I investigated the analytical and clinical performance of the measurement of the free beta-subunit of choriogonadotropin (hCG) in normal pregnancies and in pregnancies affected by Down's syndrome. Free beta-hCG in maternal serum has been shown to be increased in Down's syndrome-affected pregnancies and is proportionally increased in more cases than is total hCG. This study confirms previous findings of low concentrations of unconjugated estriol and alpha-fetoprotein in maternal serum in Down's syndrome-affected pregnancies. Using a multivariate risk analysis of maternal age and concentrations of alpha-fetoprotein, unconjugated estriol, and hCG in maternal serum, I determined that, at a risk cutoff value of 1 in 300, 52% of Down's cases could be detected with total hCG in the calculation, compared with 66% with the free beta-hCG concentration. The false-positive rate was 5.9% in both cases. Therefore, free beta-hCG can be used effectively in a screening program for Down's syndrome; however, further studies are required to ascertain whether the measurement of free beta-hCG has any advantages over the use of total hCG for detecting Down's syndrome.

Analysis of Variance↗
PubMed1989

Effect of xylazine in heifers under thermoneutral or heat stress conditions.

A study was performed to assess the effect of xylazine HCl (0.1 mg/kg of body weight, IV) in heifers maintained at thermoneutrality (18 C, 42% humidity) or under heat stress (33 C, 63% humidity) conditions. Xylazine caused 50 and 70% decreases in serum insulin concentrations in the thermoneutral and heat-stressed heifers, respectively. Xylazine-induced hypoinsulinemia was associated with hyperglycemia. In the thermoneutral group, serum glucose concentrations increased from a basal concentration of 75 mg/dl to 150 mg/dl after 15 minutes. In the heat stress group, the serum glucose concentration increased from 65 mg/dl to 105 mg/dl. Hyperglycemia peaked at 2 hours and remained high for 6 hours after xylazine administration. Heat-stressed heifers took a longer time (107 minutes) to stand than did heifers under thermoneutral conditions (41 minutes). The time to regain sensation to pain was significantly prolonged in heat-stressed heifers. Xylazine had no effect on body temperature and respiration rate in heifers under the thermoneutral condition, whereas it markedly induced hyperthermia and suppressed respiration rate in the heat-stressed heifers. Furthermore, the pulse rate was slightly decreased in thermoneutral heifers and was markedly decreased in the heat-stressed heifers.

Animals↗
PubMed1988

Neurone specific enolase in amniotic fluid: a potential marker of anencephaly.

Normal values for neurone specific enolase in amniotic fluid have been found to follow a non gaussian distribution with a 1-99 centile range of 1.10-4.32 micrograms/L. Neurone specific enolase levels have been shown to be raised in the amniotic fluid of pregnancies complicated by anencephaly, although not those complicated by open spina bifida. Neurone specific enolase measured by radioimmunoassay is capable of totally discriminating between normal pregnancies and those complicated by anencephaly. The study demonstrates the possible value of investigating other neuronal proteins which may find value as adjuncts to amniotic fluid Alpha fetoprotein levels in the prenatal diagnosis of Neural Tube Defects.

Amniotic Fluid↗