Biomedical subjects

Phillip Dinh

Publications and source records attributed to Phillip Dinh.

3 recordsLinked to original sources

PubMed2006

Nonparametric statistical methods for cost-effectiveness analyses.

Two measures often used in a cost-effectiveness analysis are the incremental cost-effectiveness ratio (ICER) and the net health benefit (NHB). Inferences on these two quantities are often hindered by highly skewed cost data. In this article, we derive the Edgeworth expansions for the studentized t-statistics for the two measures and show how they could be used to guide inferences. In particular, we use the expansions to study the theoretical performance of existing confidence intervals based on normal theory and to derive new confidence intervals for the ICER and the NHB. We conduct a simulation study to compare our new intervals with several existing methods. The methods evaluated include Taylor's interval, Fieller's interval, the bootstrap percentile interval, and the bootstrap bias-corrected acceleration interval. We found that our new intervals give good coverage accuracy and are narrower compared to the current recommended intervals.

Biometry↗

PubMed2005

Nonparametric confidence intervals for the one- and two-sample problems.

Confidence intervals for the mean of one sample and the difference in means of two independent samples based on the ordinary-t statistic suffer deficiencies when samples come from skewed families. In this article we evaluate several existing techniques and propose new methods to improve coverage accuracy. The methods examined include the ordinary-t, the bootstrap-t, the biased-corrected acceleration and three new intervals based on transformation of the t-statistic. Our study shows that our new transformation intervals and the bootstrap-t intervals give best coverage accuracy for a variety of skewed distributions, and that our new transformation intervals have shorter interval lengths.

Computer Simulation↗

PubMed2004

Rapid HIV type 1 testing of women presenting in late pregnancy with unknown HIV status in Lima, Peru.

We studied the feasibility and acceptability of HIV-1 testing using rapid serological assays in pregnant women presenting in late pregnancy without prior HIV-1 testing. Pregnant women presenting to the emergency room at the Instituto Materno-Perinatal in Lima, Peru, were offered on-site rapid HIV-1 testing. Consenting women were provided HIV counseling and had samples taken for rapid detection of antibodies in the blood and oral secretions. Women testing HIV-1 seropositive by one or both assays were offered standard HIV obstetrical care including antiretrovirals. Between October 2000 and August 2001, 3543 women were tested for HIV-1 antibodies through the rapid testing protocol. Twenty-seven women tested positive by one or both assays. Standard EIA results were negative for two of the 27 women and EIA results were not available for an additional three women. Seventeen of the 19 women (89%) for whom delivery information is available received antiretroviral therapy prior to delivery. Eighty percent of the women treated with nevirapine received the drug at least 1 hr prior to delivery. Study personnel reported problems with performing the rapid assays for less than 1% of the samples and the majority of the women did not express a preference for either the oral fluid or blood sample collection. While HIV-1 testing early in pregnancy is preferable, rapid HIV-1 testing in late pregnancy or at delivery is feasible, acceptable to most women, and allows for timely intervention to reduce maternal-child transmission.

AIDS Serodiagnosis↗