A Censored Multinomial Regression Model for Perinatal Mother to Child Transmission of HIV

In studies designed to estimate rates of perinatal mother to child transmission of HIV, HIV assays are scheduled at multiple points in time. Still infection status for some infants at some time points is often unknown, particularly when interim analyses are conducted. Logistic regression and Cox proportional hazards regression are commonly used to estimate covariate-adjusted transmission rates, but their methods for handling missing data may be inadequate. Here, we propose using censored multinomial regression models to estimate cumulative and conditional rates of HIV transmission. Through simulation, we show that the proposed methods perform better than standard logistic models in terms of bias, mean squared error, coverage probability, and power, under a range of treatment effect and visit process scenarios

Reported Mammographic Density: Film-Screen versus Digital Acquisition

To test the hypothesis that American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) categories for breast density reported by radiologists are lower when digital mammography is used than those reported when film-screen (FS) mammography is used

Performance of diagnostic mammography differs in the United States and Denmark

Diagnostic mammography is the primary imaging modality to diagnose breast cancer. However, few studies have evaluated variability in diagnostic mammography performance in communities, and none has done so between countries. We compared diagnostic mammography performance in community-based settings in the United States and Denmark. The performance of 93,585 diagnostic mammograms from 180 facilities contributing data to the U.S. Breast Cancer Surveillance Consortium (BCSC) from 1999 through 2001 was compared to that of all 51,313 diagnostic mammograms performed at Danish clinics in 2000. We used the imaging workup’s final assessment to determine sensitivity, specificity, and an estimate of accuracy: area under the receiver-operating characteristics (ROC) curve (AUC). Diagnostic mammography had slightly higher sensitivity in the United States (85%) than in Denmark (82%). In contrast, it had higher specificity in Denmark (99%) than in the United States (93%). The AUC was high in both countries: U.S. 0.91; and Denmark 0.95. Denmark’s higher accuracy may result from supplementary ultrasound examinations, which are provided to 74% of Danish women but only 37% to 52% of U.S. women. In addition, Danish mammography facilities specialize in either diagnosis or screening, possibly leading to greater diagnostic mammography expertise in facilities dedicated to symptomatic patients. Performance of community-based diagnostic mammography settings varied markedly between the two countries, indicating that it can be further optimized

A coarsened multinomial regression model for perinatal mother to child transmission of HIV

Background: In trials designed to estimate rates of perinatal mother to child transmission of HIV, HIV assays are scheduled at multiple points in time. Still, infection status for some infants at some time points may be unknown, particularly when interim analyses are conducted. Methods: Logistic regression models are commonly used to estimate covariate-adjusted transmission rates, but their methods for handling missing data may be inadequate. Here we propose using coarsened multinomial regression models to estimate cumulative and conditional rates of HIV transmission. Through simulation, we compare the proposed models to standard logistic models in terms of bias, mean squared error, coverage probability, and power. We consider a range of treatment effect and visit process scenarios, while including imperfect sensitivity of the assay and contamination of the endpoint due to early breastfeeding transmission. We illustrate the approach through analysis of data from a clinical trial designed to prevent perinatal transmission. Results: The proposed cumulative and conditional models performed well when compared to their logistic counterparts. Performance of the proposed cumulative model was particularly strong under scenarios where treatment was assumed to increase the risk of in utero transmission but decrease the risk of intrapartum and overall perinatal transmission and under scenarios designed to represent interim analyses. Power to estimate intrapartum and perinatal transmission was consistently higher for the proposed models. Conclusion: Coarsened multinomial regression models are preferred to standard logistic models for estimation of perinatal mother to child transmission of HIV, particularly when assays are missing or occur off-schedule for some infants.U.S. National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), and Dept. of Health and Human Services (DHHS)

Pregnancy Intentions and Happiness Among Pregnant Black Women at High Risk for Adverse Infant Health Outcomes

CONTEXT:Unintended pregnancy is associated with risk behaviors and increased morbidity or mortality for mothers and infants, but a woman\u27s feelings about pregnancy may be more predictive of risk and health outcomes than her intentions. METHODS: A sample of 1,044 black women who were at increased risk were enrolled at prenatal care clinics in the District of Columbia in 2001-2003. Bivariate and multivariate analyses assessed associations between pregnancy intentions or level of happiness about being pregnant and multiple psychosocial and behavioral risk factors, and identified correlates of happiness to be pregnant. RESULTS: Pregnancy intentions and happiness were strongly associated, but happiness was the better predictor of risk. Unhappy women had higher odds than happy women of smoking, being depressed, experiencing intimate partner violence, drinking and using illicit drugs (odds ratios, 1.7-2.6). The odds of being happy were reduced among women who had other children or a child younger than two, who were single or did not have a current partner, who had had more than one sexual partner in the past year and who reported that the baby\u27s father did not want the pregnancy (0.3-0.6). In contrast, the odds of being happy were elevated among women who had better coping strategies (1.03), who had not used birth control at conception (1.6) and who had 1-2 household members, rather than five or more (2.1). CONCLUSIONS: Additional psychosocial screening for happiness about being pregnant and for partner characteristics, particularly the father\u27s desire to have this child, may help improve prenatal care services and prevent adverse health outcomes

Rehospitalization of extremely low birth weight (ELBW) infants: are there racial/ethnic disparities?

Premature infants are at increased risk for rehospitalization after discharge from the hospital. Racial disparities are known to exist in pediatric health care. To evaluate whether racial disparities exist in the proportion of extremely low birth weight (ELBW) infants rehospitalized prior to 18 months corrected age and the causes of rehospitalization. The National Institute of Child Health and Human Development Neonatal Research Network database was used to identify all ELBW infants (n=2446) who were born between November 1, 1998 and May 31, 2000 at the 14 participating centers and discharged alive (n=1591). Infants were seen at 18-22 months corrected age for followup. Data related to maternal variables, race, socioeconomic status, medical morbidities, insurance, and rehospitalizations were recorded from the medical record and parent interview. Logistic regression analyses were used to examine the relationship of race/ethnicity and rehospitalization while controlling for gestational age, gender, center, maternal education, family income, bronchopulmonary dysplasia (BPD), necrotizing enterocolitis, ventriculoperitoneal (VP) shunt, respiratory syncytial virus (RSV) prophylaxis, and insurance type. In all, 1405 (88%) infants were evaluated at followup. The racial distribution of infants admitted, discharged, seen at followup, and rehospitalized were similar. Rehospitalization occurred at least once in 49% of the infants. In the logistic regression analyses, race was not a significant predictor for rehospitalization. The odds of rehospitalization were related to low family income, type of insurance, BPD, VP shunt, RSV prophylaxis, and center. Race was not a predominant variable in the risk of rehospitalization in this cohort of ELBW infants. Medical morbidities and low family income appear to be the major risk factors for rehospitalization

Livestock grazing limits beaver restoration in northern New Mexico

The North American beaver (Castor canadensis) builds dams that pond water on streams, which provide crucial ecologicalservices to aquatic and riparian ecosystems and enhance biodiversity. Consequently, there is increasing interest in restoringbeavers to locations where they historically occurred, particularly in the arid western United States. However, despiteoften intensive efforts to reintroduce beavers into areas where they were severely reduced in numbers or eliminated dueto overharvesting in the eighteenth and nineteenth centuries, beavers remain sparse or missing from many stream reaches.Reasons for this failure have not been well studied. Our goal was to evaluate certain biotic factors that may limit the occurrenceof dam-building beavers in northern New Mexico, including competitors and availability of summer and winter forage. Wecompared these factors at primary active dams and at control sites located in stream reaches that were physically suitable fordam-building beavers but where none occurred. Beaver dams mostly occurred at sites that were not grazed or where therewas some alternative grazing management, but were mostly absent at sites within Forest Service cattle allotments. Resultsindicated that cattle grazing inuenced the relation between vegetation variables and beaver presence. The availability ofwillows (Salix spp.) was the most important plant variable for the presence of beaver dams. We conclude that grazing by cattleas currently practiced on Forest Service allotments disrupts the beaver-willow mutualism, rendering stream reaches unsuitablefor dam-building beavers. We recommend that beaver restoration will require changes to current livestock managementpractices