| 231. |
- Otwombe, K. N., et al.
(författare)
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Factors associated with mortality in HIV-infected people in rural and urban South Africa
- 2014
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Ingår i: Global Health Action. - : Informa UK Limited. - 1654-9880 .- 1654-9716. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Background: Factors associated with mortality in HIV-infected people in sub-Saharan Africa are widely reported. However rural-urban disparities and their association with all-cause mortality remain unclear. Furthermore, commonly used classical Cox regression ignores unmeasured variables and frailty. Objective: To incorporate frailty in assessing factors associated with mortality in HIV-infected people in rural and urban South Africa. Design: Using data from a prospective cohort following 6,690 HIV-infected participants from Soweto (urban) and Mpumalanga (rural) enrolled from 2003 to 2010; covariates of mortality were assessed by the integrated nested Laplace approximation method. Results: We enrolled 2,221 (33%) rural and 4,469 (67%) urban participants of whom 1,555 (70%) and 3,480 (78%) were females respectively. Median age (IQR) was 36.4 (31.0-44.1) in rural and 32.7 (28.2-38.1) in the urban participants. The mortality rate per 100 person-years was 11 (9.7-12.5) and 4 (3.6-4.5) in the rural and urban participants, respectively. Compared to those not on HAART, rural participants had a reduced risk of mortality if on HAART for 6-12 (HR: 0.20, 95% CI: 0.10-0.39) and >12 months (HR: 0.10, 95% CI: 0.05-0.18). Relative to those not on HAART, urban participants had a lower risk if on HAART >12 months (HR: 0.35, 95% CI: 0.27-0.46). The frailty variance was significant and >1 in rural participants indicating more heterogeneity. Similarly it was significant but <1 in the urban participants indicating less heterogeneity. Conclusion: The frailty model findings suggest an elevated risk of mortality in rural participants relative to the urban participants potentially due to unmeasured variables that could be biological, socio-economic, or healthcare related. Use of robust methods that optimise data and account for unmeasured variables could be helpful in assessing the effect of unknown risk factors thus improving patient management and care in South Africa and elsewhere.
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| 232. |
- Petzold, Max, 1973
(författare)
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A comprative study of some approaches for constructing tolerance limits
- 2000
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In a dose finding study the aim is to come up with a safe and efficient drug administration. By comparing the obtained tolerance limits with predetermined desired concentration limits, i.e. the therapeutic window, one may be able to adjust the drug dosage. For drugs with a therapeutic window situated at high concentrations close to toxic levels, one has to balance between attaining a high proportion of the population at efficient high levels on one hand and the risks of an overdose on the other hand. In such cases it is important to use the proper estimation approach for the upper tolerance limit. Here a conservative estimation approach intended for a drug with potentially adverse side effects with minor overdoses is compared with an approach intended for a drug with harmless side effects. It is shown that the conservative approach can be considerably less efficient when used in the latter case, a disadvantage that is rarely discussed when proposing conservative estimators. The properties of the two approaches are evaluated using well-known parametric and non-parametric estimators in a simulation study for small and moderate sample sizes.
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| 233. |
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| 234. |
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| 235. |
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| 236. |
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| 237. |
- Petzold, Max, 1973, et al.
(författare)
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Introducing Innovative Indicators to Track Sweden's Open Research Data Objective: How to Measure Progress? Defining Indicators to Track Open Research Data Across Swedish Universities
- 2023
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Ingår i: Research Data Alliance 20th Plenary Meeting (RDA P20), March 21-23, Gothenburg, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Sweden has set an ambitious objective to make all their research data open by 2026. In order to achieve this, there needs to be individual and institutional behavior changes and a framework to track these changes and progress. The Swedish National Data Service, together with Stockholm University, Karolinska Institutet, University of Gothenburg, and Elsevier have started initial discussions to identify the right indicators to track progress. In this workshop we will present the early results from the pilot project, including a framework of indicators that can be used to track progress. The pilot indicator data have been extracted from open metadata sources as well as from Elsevier's publication indexing. We will also demonstrate how these indicators can be used to identify gaps and challenges in the current data sharing practices. In addition, practical insights arising from the project will be discussed, as well as opportunities and challenges that this effort presents. Participants will have the opportunity to join the discussion and share their own experiences with similar initiatives. By means of sharing these insights, we hope to inspire others and stimulate a global dialogue on the topic and leverage existing efforts rather than reinventing the wheel. Results and conclusions will be distributed under the EOSC association umbrella. We hope to to receive feedback from attendees/RDA Community on the proposed framework of indicators and learn about existing best practices.
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| 238. |
- Petzold, Max, 1973, et al.
(författare)
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Maximum Likelihood Ratio based small- sample tests for random coefficients in linear regression
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Two small-sample tests for random coefficients in linear regression are derived from the Maximum Likelihood Ratio. The first test has previously been proposed for testing equality of fixed effects, but is here shown to be suitable also for random coefficients. The second test is based on the multiple coefficient of determination from regressing the observed subject means on the estimated slopes. The properties and relations of the tests are examined in detail, followed by a simulation study of the power functions. The two tests are found to complement each other depending on the study design: The first test is preferred for a large number of observations from a small number of subjects, and the second test is preferred for the opposite situation. Finally, the robustness of the tests to violations of the distributional assumptions is examined.
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| 239. |
- Petzold, Max, 1973, et al.
(författare)
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Surveillance in Longitudinal Models: Detection of Intrauterine Growth Restriction
- 2004
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Ingår i: Biometrics. - 0006-341X. ; 60:4, s. 1025-1033:60, s. 1025-1033
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Tidskriftsartikel (refereegranskat)abstract
- Summary. A new methodology for online detection of intrauterine growth restriction (IUGR) is proposed where traditional methods for statistical surveillance are applied. Here, deficient growth rate is used to detect IUGR instead of the common surrogate measure "small for gestational age" (SGA). Fetal growth is estimated by repeated measurements of symphysis-fundus (SF) height. At each time point the new method, based on the Shiryaev-Roberts method, is used to evaluate the growth in SF height. We use Swedish data to model a normal growth pattern, which is used to evaluate the capability of the new method to detect IUGR in comparison with a method used in practice today. Results from simulations indicate that the new method performs considerably better than the method used today. We also illustrate the effect of some important factors which influence the detection ability and illuminate the tendency of the method used today to misclassify SGA cases as IUGR.
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| 240. |
- Pohjonen, E-M, et al.
(författare)
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Obstetric and perinatal risks after the use of donor sperm: A systematic review and meta-analysis.
- 2022
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Ingår i: European journal of obstetrics, gynecology, and reproductive biology. - : Elsevier BV. - 1872-7654 .- 0301-2115. ; 274, s. 210-228
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Tidskriftsartikel (refereegranskat)abstract
- Donor sperm is widely used in infertility treatments. The purpose of the study was to investigate, whether use of donor sperm in intrauterine insemination (IUI) or in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) treatments affect maternal and perinatal risks compared with spontaneously conceived pregnancies or use of partner sperm in IUI, IVF or ICSI. We provide a systematic review and meta-analyses on the most clinically relevant obstetric and perinatal outcomes after use of donor sperm compared with partner sperm: hypertensive disorders of pregnancy, preeclampsia, low birth weight, and preterm birth. Our meta-analyses showed an increased risk for preeclampsia (pooled adjusted odds ratio (aOR) 1.77, 95% CI 1.26-2.48) and hypertensive disorders of pregnancy (pooled aOR 1.55, 95%, CI 1.20-2.00) in pregnancies resulting from IUI with donor sperm compared with IUI with partner sperm. No increased risk was seen for low birth weight or preterm birth after the use of donor sperm in IUI compared with the use of partner sperm in IUI. Subgroup analysis for singletons only did not change these results. The meta-analysis on low birth weight showed a lower risk after in IVF with donor sperm compared with IVF with partner sperm (pooled aOR 0.89, 95% CI 0.83-0.94). For hypertensive disorders of pregnancy, preeclampsia and preterm birth, no difference was found between IVF with donor sperm vs. partner sperm. Patients need to be informed about the moderately increased risk of hypertensive disorders of pregnancy and preeclampsia in pregnancies after IUI with donor sperm.
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