Discussion: Conditional growth charts

Discussion of Conditional growth charts [math.ST/0702634]Comment: Published at http://dx.doi.org/10.1214/009053606000000650 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

The use (and abuse) of reference centiles with an application to weight gain in pregnancy

Centile charts are commonly used in many areas of health research and practice, e.g. growth charts for children, Doppler ultrasonography in pregnancy and assessment of cholesterol levels at different ages. Yet there are a number of aspects of both their construction and application that are problematic and it is some of these issues that will be raised in this paper.The objective of the paper is to outline, in a non-technical way, some of the issues that need to be considered by the practitioner in estimating and using reference centile charts, but which frequently are either not known or ignored. These include: (i) the choice of reference population; (ii) how to estimate centiles; (iii) formally incorporating previous measurements on an individual, e.g. the interpretation of a child's weight that is on the 50th percentile for its age will be different if it has been moving along the 90th percentile at previous ages than if it has consistently been on the 50th percentile; and (iv) evaluation of centile charts used as a screen for problems.The concepts are introduced using an aspect of a study conducted at Tygerberg Hospital where centile charts for maternal weight gain in pregnancy were developed andassessed for their usefulness in detecting light-forgestational-age (UGA) births. The reference centile charts for maternal weight show poor discriminating ability between LiGA and nonnal births. These results support arguments in favour of abandoning the routine weighing of pregnant women

Statistical modelling to predict silicosis risk in deceased Southern African gold miners without medical evaluation

The Qhubeka Trust was established in 2016 in a legal settlement on behalf of former gold miners seeking compensation for silicosis contracted on the South African mines. Settlements resulting from lawsuits on behalf of gold miners aim to provide fair compensation. However, occupational exposure and medical records kept by South African mining companies for their employees have been very limited. Some claimants to the Qhubeka Trust died before medical evaluation was possible, thus potentially disadvantaging their dependants from receiving any compensation. With medical evaluation no longer possible, a statistical approach to this problem was developed. The records for claimants with medical evaluation were used to develop a logistic regression prediction model for the likelihood of silicosis, based on the potential predictors: cumulative exposure to respirable dust, age, years since first exposure, years of life lost prematurely, vital status at 31 December 2019, and a history of tuberculosis diagnosis. The prediction model allowed estimation of the likelihood of silicosis for each miner who had died without medical evaluation and is a novel approach in this setting. In addition, we were able to quantitatively evaluate the trade-offs of different silicosis risk classification thresholds in terms of true and false positives and negatives. Significance:• A statistical approach can be used for risk estimation in settings where the outcome of interest is unknown for some members of a class.• The likelihood of silicosis in deceased miners without medical evaluation in the Qhubeka Trust can be accurately estimated, using information from finalised claims.• Strategies for classifying the silicosis status of deceased miners without medical evaluation in theQhubeka Trust can be assessed in a rigorous, quantitative framework

Prospectus, February 20, 1985

https://spark.parkland.edu/prospectus_1985/1003/thumbnail.jp

Violence, alcohol and symptoms of depression and in Cape Town's poorest communities: results of a community survey

Introduction This paper summarises key findings from the first of three household surveys conducted in three high-violence areas in the Cape Town, investigating community members’ experiences of alcohol use, their built environment, violence and symptoms of depression, together with their views on alcohol and other interventions. Methods A stratified random sample of 1500 dwellings, 1200 in Khayelitsha and 300 in Gugulethu and Nyanga (“Gunya”) was selected using GIS address data for formal areas and aerial photography for informal areas. Fieldwork took place from July to November 2013. Responses to questions were summarized by area, gender, age and formal vs. informal settlement type. Results After substitution and data cleaning, 1213 Khayelitsha households and 286 Gunya households were included. In Gunya, 29% of respondents reported that they or their family members had been affected by at least one violent crime (murder, assault, domestic violence, rape) in the past year, compared with 12% in Khayelitsha. Using a CES-D-10 cut-off of 10, 44% of respondents were classified as depressed. More than half the respondents reported having experienced some form of alcohol nuisance. Respondents were supportive of alcohol interventions such as increased taxes and police regulation of outlets, particularly in Gunya (87%) and amongst female respondents (76%). Satisfaction with infrastructure such as street lighting and drainage was generally low. Conclusions The results describe the co-occurring burdens of alcohol and drug use, violence, depression and deprivation in our study populations

Prospectus, March 13, 1985

https://spark.parkland.edu/prospectus_1985/1006/thumbnail.jp

Bismuth coordination networks containing deferiprone: synthesis, characterisation, stability and antibacterial activity

A series of bismuth–dicarboxylate–deferiprone coordination networks have been prepared and structurally characterised. The new compounds have been demonstrated to release the iron overload drug deferiprone on treatment with PBS and have also been shown to have antibacterial activity against H. pylori