Impact of Missing Data for Body Mass Index in an Epidemiologic Study

To assess the potential impact of missing data on body mass index (BMI) on the association between prepregnancy obesity and specific birth defects

Detection of Pelvic Inflammatory Disease: Development of an Automated Case-Finding Algorithm Using Administrative Data

ICD-9 codes are conventionally used to identify pelvic inflammatory disease (PID) from administrative data for surveillance purposes. This approach may include non-PID cases. To refine PID case identification among women with ICD-9 codes suggestive of PID, a case-finding algorithm was developed using additional variables. Potential PID cases were identified among women aged 15–44 years at Group Health (GH) and Kaiser Permanente Colorado (KPCO) and verified by medical record review. A classification and regression tree analysis was used to develop the algorithm at GH; validation occurred at KPCO. The positive predictive value (PPV) for using ICD-9 codes alone to identify clinical PID cases was 79%. The algorithm identified PID appropriate treatment and age 15–25 years as predictors. Algorithm sensitivity (GH = 96.4%; KPCO = 90.3%) and PPV (GH = 86.9%; KPCO = 84.5%) were high, but specificity was poor (GH = 45.9%; KPCO = 37.0%). In GH, the algorithm offered a practical alternative to medical record review to further improve PID case identification

"Toward a Clearer Definition of Confounding" Revisited With Directed Acyclic Graphs

In a 1993 paper (Am J Epidemiol. 1993;137(1):1–8), Weinberg considered whether a variable that is associated with the outcome and is affected by exposure but is not an intermediate variable between exposure and outcome should be considered a confounder in etiologic studies. As an example, she examined the common practice of adjusting for history of spontaneous abortion when estimating the effect of an exposure on the risk of spontaneous abortion. She showed algebraically that such an adjustment could substantially bias the results even though history of spontaneous abortion would meet some definitions of a confounder. Directed acyclic graphs (DAGs) were introduced into epidemiology several years later as a tool with which to identify confounders. The authors now revisit Weinberg's paper using DAGs to represent scenarios that arise from her original assumptions. DAG theory is consistent with Weinberg's finding that adjusting for history of spontaneous abortion introduces bias in her original scenario. In the authors' examples, treating history of spontaneous abortion as a confounder introduces bias if it is a descendant of the exposure and is associated with the outcome conditional on exposure or is a child of a collider on a relevant undirected path. Thoughtful DAG analyses require clear research questions but are easily modified for examining different causal assumptions that may affect confounder assessment

Immunohistochemical detection of macrophage migration inhibitory factor in fetal and adult bovine epididymis: Release by the apocrine secretion mode?

Originally defined as a lymphokine inhibiting the random migration of macrophages, the macrophage migration inhibitory factor (MIF) is an important mediator of the host response to infection. Beyond its function as a classical cytokine, MIF is currently portrayed as a multifunctional protein with growth-regulating properties present in organ systems beyond immune cells. In previous studies, we detected substantial amounts of MIF in the rat epididymis and epididymal spermatozoa, where it appears to play a role during post-testicular sperm maturation and the acquisition of fertilization ability. To explore its presence in other species not yet examined in this respect, we extended the range of studies to the bull. Using a polyclonal antibody raised against MIF purified from bovine eye lenses, we detected MIF in the epithelium of the adult bovine epididymis with the basal cells representing a prominently stained cell type. A distinct accumulation of MIF at the apical cell pole of the epithelial cells and in membranous vesicles localized in the lumen of the epididynnal duct was obvious. In the fetal bovine epididymis, we also detected MIF in the epithelium, whereas MIF accumulation was evident at the apical cell surface and in apical protrusions. By immuno-electron microscopy of the adult bovine epididymis, we localized MIF in apical protrusions of the epithelial cells and in luminal membrane-bound vesicles that were found in close proximity to sperm cells. Although the precise origin of the MIF-containing vesicles remains to be delineated, our morphological observations support the hypothesis that they become detached from the apical surface of the epididymal epithelial cells. Additionally, an association of MIF with the outer dense fibers of luminal spermatozoa was demonstrated. Data obtained in this study suggest MIF release by an apocrine secretion mode in the bovine epididymis. Furthermore, MIF localized in the basal cells of the epithelium and in the connective tissue could be responsible for regulating the migration of macrophages in order to avoid contact of immune cells with spermatozoa that carry a wide range of potent antigens. Copyright (c) 2006 S. Karger AG, Basel

The association between gestational weight gain z-score and stillbirth: a case-control study

Background There is limited information on potentially modifiable risk factors for stillbirth, such as gestational weight gain (GWG). Our purpose was to explore the association between GWG and stillbirth using the GWG z−score. Methods We analyzed 479 stillbirths and 1601 live births from the Stillbirth Collaborative Research Network case−control study. Women with triplets or monochorionic twins were excluded from analysis. We evaluated the association between GWG z−score (modeled as a restricted cubic spline with knots at the 5th, 50th, and 95th percentiles) and stillbirth using multivariable logistic regression with generalized estimating equations, adjusting for pre − pregnancy body mass index (BMI) and other confounders. In addition, we conducted analyses stratified by pre − pregnancy BMI category (normal weight, overweight, obese). Results Mean GWG was 18.95 (SD 17.6) lb. among mothers of stillbirths and 30.89 (SD 13.3) lb. among mothers of live births; mean GWG z−score was − 0.39 (SD 1.5) among mothers of cases and − 0.17 (SD 0.9) among control mothers. In adjusted analyses, the odds of stillbirth were elevated for women with very low GWG z−scores (e.g., adjusted odds ratio (aOR) and 95% Confidence Interval (CI) for z−score − 1.5 SD versus 0 SD: 1.52 (1.30, 1.78); aOR (95% CI) for z−score − 2.5 SD versus 0 SD: 2.36 (1.74, 3.20)). Results differed slightly by pre − pregnancy BMI. The odds of stillbirth were slightly elevated among women with overweight BMI and GWG z−scores ≥1 SD (e.g., aOR (95% CI) for z−score of 1.5 SD versus 0 SD: 1.84 (0.97, 3.50)). Conclusions GWG z−scores below − 1.5 SD are associated with increased odds of stillbirth

Abundances of Iron-Binding Photosynthetic and Nitrogen-Fixing Proteins of Trichodesmium Both in Culture and In Situ from the North Atlantic

Marine cyanobacteria of the genus Trichodesmium occur throughout the oligotrophic tropical and subtropical oceans, where they can dominate the diazotrophic community in regions with high inputs of the trace metal iron (Fe). Iron is necessary for the functionality of enzymes involved in the processes of both photosynthesis and nitrogen fixation. We combined laboratory and field-based quantifications of the absolute concentrations of key enzymes involved in both photosynthesis and nitrogen fixation to determine how Trichodesmium allocates resources to these processes. We determined that protein level responses of Trichodesmium to iron-starvation involve down-regulation of the nitrogen fixation apparatus. In contrast, the photosynthetic apparatus is largely maintained, although re-arrangements do occur, including accumulation of the iron-stress-induced chlorophyll-binding protein IsiA. Data from natural populations of Trichodesmium spp. collected in the North Atlantic demonstrated a protein profile similar to iron-starved Trichodesmium in culture, suggestive of acclimation towards a minimal iron requirement even within an oceanic region receiving a high iron-flux. Estimates of cellular metabolic iron requirements are consistent with the availability of this trace metal playing a major role in restricting the biomass and activity of Trichodesmium throughout much of the subtropical ocean

Diabetes mellitus, smoking status, and rate of sputum culture conversion in patients with multidrug-resistant tuberculosis: a cohort study from the country of Georgia.

Diabetes mellitus (DM) is a risk factor for active tuberculosis (TB) but little is known about the effect of DM on culture conversion among patients with multidrug-resistant (MDR)-TB. The primary aim was to estimate the association between DM and rate of TB sputum culture conversion. A secondary objective was to estimate the association between DM and the risk of poor treatment outcomes among patients with MDR-TB.A cohort of all adult patients starting MDR-TB treatment in the country of Georgia between 2009-2011 was followed during second-line TB therapy. Cox proportional models were used to estimate the adjusted hazard rate of sputum culture conversion. Log-binomial regression models were used to estimate the cumulative risk of poor TB treatment outcome.Among 1,366 patients with sputum culture conversion information, 966 (70.7%) had culture conversion and the median time to conversion was 68 days (interquartile range 50-120). The rate of conversion was similar among patients with MDR-TB and DM (adjusted hazard ratio [aHR] 0.95, 95%CI 0.71-1.28) compared to patients with MDR-TB only. The rate of culture conversion was significantly less in patients that currently smoked (aHR 0.82, 95%CI 0.71-0.95), had low body mass index (aHR 0.71, 95%CI 0.59-0.84), second-line resistance (aHR 0.56, 95%CI 0.43-0.73), lung cavities (aHR 0.70, 95%CI 0.59-0.83) and with disseminated TB (aHR 0.75, 95%CI 0.62-0.90). The cumulative risk of poor treatment outcome was also similar among TB patients with and without DM (adjusted risk ratio [aRR] 1.03, 95%CI 0.93-1.14).In adjusted analyses, DM did not impact culture conversion rates in a clinically meaningful way but smoking did