An empirical Bayes approach to estimating the relation of mortality to exposure to particulate matter.

As part of its assessment of the health risks associated with exposure to particulate matter (PM), the U.S. Environmental Protection Agency analyzed the risks associated with current levels, and the risk reductions that might be achieved by attainment of alternative PM standards, in two locations in the United States, Philadelphia, and Los Angeles. The concentration-response function describing the relation between a health endpoint and ambient PM concentrations is an important component, and a source of substantial uncertainty, in such risk analyses. In the absence of location-specific estimates, the concentration-response functions necessary for risk assessments in Philadelphia and Los Angeles must be inferred from the available information in other locations. Although the functional form of the concentration-response relations is assumed to be the same everywhere, the value of the PM coefficient in that function may vary from one location to another. Under this model, a distribution describes the probability that the PM coefficient in a randomly selected location will lie in any range of interest. An empirical Bayes estimation technique was used to improve the estimation of location-specific concentration-response functions relating mortality to short-term exposure to particles of aerodynamic diameter less than or equal to 2.5 microm (PM-2.5), for which functions have previously been estimated in several locations. The empirical Bayes-adjusted parameter values and their SEs were used to derive an estimate of the distribution of PM-2.5 coefficients for mortality associated with short-term exposures. From this distribution, distributions of relative risks corresponding to different specified changes in PM-2.5 concentrations could be derived.

Statistical issues for HIV surrogate endpoints: point/counterpoint. An NIAID workshop.

This paper summarizes the proceedings of an NIAID-sponsored workshop on statistical issues for HIV surrogate endpoints. The workshop brought together statisticians and clinicians in an attempt to shed light on some unresolved issues in the use of HIV laboratory markers (such as HIV RNA and CD4+ cell counts) in the design and analysis of clinical studies and in patient management. Utilizing a debate format, the workshop explored a series of specific questions dealing with the relationship between markers and clinical endpoints, and the choice of endpoints and methods of analysis in clinical studies. This paper provides the position statements from the two debaters on each issue. Consensus conclusions, based on the presentations and discussion, are outlined. While not providing final answers, we hope that these discussions have helped clarify a number of issues, and will stimulate further consideration of some of the highlighted problems. These issues will be critical in the proper assessment and use of future therapies for HIV disease.

Risk factors for work-related violent victimization.

This case-control study used the National Crime Victimization Survey database (a national sample of housing addresses) to examine sociodemographic risk factors for becoming a victim of work-related robbery and assault. Cases (N = 267) reported having been violently victimized in the previous 6 months. Controls (N = 1,783) were chosen from all nonvictims of violent crime at the end of the 6-month period. Risk factors varied by type of victimization, and differences were evident between men and women. Men less than 45 years of age had an increased risk for assault [odds ratio (OR) = 2.0-2.7], compared with those 55 years of age and older; and those with a family income of less than $40,000 had an increased risk for assault (OR = 1.7-1.9), compared with those having a family income of $50,000 or more. We found a decreased risk for those with a high school education (OR = 0.6), compared with those with some college education. For women, an increased risk was seen for ages 16-18 years (OR = 3.3) and 25-34 years (OR = 2.3), compared with those 55 years of age or older. Women who were divorced or separated (OR = 4.4) and never-married (OR = 2.1) were at higher risk than women who were married. We found a decreased risk for nonwhites (OR = 0.5), compared with whites.

Data analysis issues for protocols with overlapping enrollment.

Many persons with HIV require and take several medications. The efficacy and safety of many of these medications are uncertain. Usually limited data on drug interactions are available. Thus simultaneous and sequential enrolment of patients into multiple studies is desired for reasons of science and efficiency. This paper discusses the analysis of data arising from coenrolment in multiple studies sponsored by the Community Programs for Clinical Research on AIDS (CPCRA). Factorial designs and those in which patients are sequentially instead of simultaneously randomized are compared. Approaches to data analysis, based on intention-to-treat, for individual and pairs of trials are described. An antiretroviral trial and a trial for prophylaxis of Pneumocystis carinii pneumonia (PCP) are used for illustration. We conclude that such analyses may yield useful information on drug interactions and that a more vigorous coenrolment policy should be pursued in AIDS research.

Perceptions of garment proportions by female observers.

One hundred seventy-two undergraduate women responded to twelve sets of stimuli consisting of a constant jacket silhouette varying proportionally in components of lapel, yoke, and pocket details. Using a 9-point scale in Likert format, the subjects were asked to respond to questions comparing the jacket stimuli of each set in terms of same/different, unattractive/attractive, unwearable/wearable, unfashionable/fashionable, not acceptable/acceptable, and dislike/like. This jacket was varied in its component parts to correspond to proportions currently available in Petite and Misses size apparel. Analysis indicated that subjects detected differences in proportions of garment details within the context of a petite jacket silhouette and preferred proportions adjusted to the smaller size.

Dietary guar gum halts further renal enlargement in rats with established diabetes.

Guar gum, a dietary fiber known to improve glucose tolerance, was fed to rats with established diabetes to determine its effect on renal enlargement and microalbuminuria. Diabetic rats were fed a modified AIN-76A (basal) diet for 4 wk, at which time half the rats continued to receive the same basal diet (DB-BA group) and half were switched to a 5% guar gum diet (DB-GG group). Nondiabetic rats fed the basal diet served as controls (NRL group). After 8 additional weeks the animals were killed. Glycated hemoglobin, a measure of long-term blood glucose control, was 14.4% in the DB-BA group and 12.4% in the DB-GG group, a statistically significant difference (P < 0.05). Kidney weight of the DB-BA group (3.51 g) was significantly greater than that of the DB-GG group (2.76 g) (P < 0.05). Eight weeks after induction of diabetes, 24-h urinary albumin excretion was highest in the DB-BA group and lowest in the NRL group; excretion in the DB-GG group (4 wk of guar feeding) was intermediate. However, by 12 wk no differences in albumin excretion among the groups were apparent. These results suggest that guar gum may be useful for slowing the progression of diabetic nephropathy and that guar gum deserves further study in this regard.

Phosphorus availability bioassay using bone ash and bone densitometry as response criteria.

Two experiments were conducted to examine the relative precision of bone densitometry and bone ash methodologies as response criteria in measurement of bioavailability of phosphorus from various supplements for turkeys. Multivariate analyses of variance were used to analyze data collected. Coefficients of correlation and variation and F ratios were used for evaluation. Bone densitometry with one scan at each of 3 points on the bone was faster than bone ash and as precise as bone ash analysis in measuring phosphorus availability in turkeys. The coefficient of correlation between percentage ash (of dry bone) and scan density (milligrams per centimeter length of bone) measurements for treatment effects was .986. The coefficient of variation was about the same for the bone ash (5.8) and the three-point bone scan (6.9) methods. As indicated by the F ratio for testing treatment effects, bone densitometry was better able to detect differences among phosphorus sources. A technician may scan 50 cleaned bones in 3 hr, but with the bone ash method, drying, ashing, and weighing may require 3 working days. Bone sampling technique, multiple operators, different bone sizes, and decay of iodine source were the major factors affecting precision of the bone densitometry technique. Relative biological availabilities of phosphorus from various supplements were about the same by the two methods.

The influence of cholecystokinin, vasoactive intestinal peptide and secretin on pancreatic and biliary secretion in laying hens.

White Leghorn hens, 14-29 weeks old, were surgically fitted with cannulas for collecting pancreatic and biliary secretions, and a jugular cannula for continuous infusion of either cholecystokinin (CCK), vasoactive intestinal peptide (VIP), or secretin. As compared to secretory levels during saline infusion, CCK significantly stimulated biliary flow and biliverdin concentration in bile; VIP significantly depressed biliverdin concentration but enhanced bicarbonate secretion in both pancreatic and biliary secretions, and also increased total pancreatic flow. Secretin depressed biliary flow and increased pancreatic bicarbonate release. The principal hormonal regulator of biliary secretion appears to be CCK, and that of pancreatic secretion to be VIP.

Growth of environmental mastitis pathogens in various bedding materials.

The objective of the study was to determine whether, under controlled conditions, bedding materials vary in their ability to support growth of different environmental pathogens independent of the presence of feces, urine, or other contamination. Five sterilized bedding materials (fine hardwood chips, recycled dried manure, chopped newspaper, softwood sawdust, and chopped straw) and three bacterial species (Escherichia coli, Klebsiella pneumoniae, and Streptococcus uberis) were used for a total of 15 bedding/bacteria combinations, replicated in three trials. Samples were incubated at 37 degrees C, and bacterial counts were determined over 5 d. Rapid growth was seen in straw and recycled manure, some growth occurred in hardwood chips, and a rapid decline in bacterial counts was observed in paper and softwood sawdust. In general, K. pneumoniae and E. coli showed more rapid growth or less rapid decline than did S. uberis. These results demonstrate that clean, damp bedding may support bacterial growth and suggest that high bacterial counts under barn conditions are influenced by factors more complex than type of bedding used.

The relationship of histrionic personality disorder to antisocial personality and somatization disorders.

The authors examined the association of antisocial personality disorder, somatization disorder, and histrionic personality disorder, both within individuals and within families, in 250 patients. All three disorders overlapped considerably within individuals; the strongest relationship was between antisocial personality and histrionic personality. A high prevalence of antisocial personality was reported in the families of patients with somatization disorder but not in the families of patients with histrionic personality. The authors suggest that histrionic individuals develop antisocial personality if they are male and somatization disorder if female; moreover, all three conditions may represent alternative manifestations or different stages of the same underlying diathesis.