Left, right and interval bivariate censored data: Evaluating screening mammography in the presence of lead -time bias, length bias and over-detection

Of the large clinical trials evaluating screening mammography efficacy, none included women ages 75 and older. Recommendations on an upper age limit at which to discontinue screening are based on indirect evidence and are not consistent. Screening mammography is evaluated using observational data from the SEER-Medicare linked database. Measuring the benefit of screening mammography is difficult due to the impact of lead-time bias, length bias and over-detection. The underlying conceptual model divides the disease into two stages: pre-clinical (T0) and symptomatic (T1) breast cancer. Treating the time in these phases as a pair of dependent bivariate observations, (t0,t1), estimates are derived to describe the distribution of this random vector. To quantify the effect of screening mammography, statistical inference is made about the mammography parameters that correspond to the marginal distribution of the symptomatic phase duration (T1). This shows the hazard ratio of death from breast cancer comparing women with screen-detected tumors to those detected at their symptom onset is 0.36 (0.30, 0.42), indicating a benefit among the screen-detected cases. ^

Detection of nonrandom association of alleles from the distribution of the number of heterozygous loci in a sample.

The distribution of the number of heterozygous loci in two randomly chosen gametes or in a random diploid zygote provides information regarding the nonrandom association of alleles among different genetic loci. Two alternative statistics may be employed for detection of nonrandom association of genes of different loci when observations are made on these distributions: observed variance of the number of heterozygous loci (s2k) and a goodness-of-fit criterion (X2) to contrast the observed distribution with that expected under the hypothesis of random association of genes. It is shown, by simulation, that s2k is statistically more efficient than X2 to detect a given extent of nonrandom association. Asymptotic normality of s2k is justified, and X2 is shown to follow a chi-square (chi 2) distribution with partial loss of degrees of freedom arising because of estimation of parameters from the marginal gene frequency data. Whenever direct evaluations of linkage disequilibrium values are possible, tests based on maximum likelihood estimators of linkage disequilibria require a smaller sample size (number of zygotes or gametes) to detect a given level of nonrandom association in comparison with that required if such tests are conducted on the basis of s2k. Summarization of multilocus genotype (or haplotype) data, into the different number of heterozygous loci classes, thus, amounts to appreciable loss of information.

Factors associated with hospital admission of elder cardiovascular patients in an emergency center

Context. Healthcare utilization of elder cardiovascular patients in United States will increase in near future, due to an aging population. This trend could burden urban emergency centers, which have become a source of primary care. ^ Objective. The objective of this study was to determine the association of age, gender, ethnicity, insurance and other presenting variables on hospital admission in an emergency center for elder cardiovascular patients. ^ Design, setting and participants. An anonymous retrospective review of emergency center patient login records of an urban emergency center in the years 2004 and 2005 was conducted. Elder patients (age ≥ 65 years) with cardiovascular disease (ICD91 390-459) were included. Multivariate logistic regression analysis was used to identify independent factors for hospital admission. Four major cardiovascular reasons for hospitalisation – ischemic heart disease, heart failure, hypertensive disorders and stroke were analysed separately. ^ Results. The number of elder patients in the emergency center is increasing, the most common reason for their visit was hypertension. Majority (59%) of the 12,306 elder patients were female. Forty five percent were uninsured and 1,973 patients had cardiovascular disease. Older age (OR 1.10; CI 1.02-1.19) was associated with a marginal increase in hospital admission in elder stroke patients. Elder females compared to elder males were more likely to be hospitalised for ischemic heart disease (OR 2.71; CI 1.22-6.00) and heart failure (OR 1.58; CI 1.001-2.52). Furthermore, insured elder heart failure patients (OR 0.54; CI 0.31-0.93) and elder African American heart failure patients (OR 0.32; CI 0.13-0.75) were less likely to be hospitalised. Ambulance use was associated with greater hospital admissions in elder cardiovascular patients studied, except for stroke. ^ Conclusion. Appropriate health care distribution policies are needed for elder patients, particularly elder females, uninsured, and racial/ethnic minorities. These findings could help triage nurse evaluations in emergency centers to identify patients who were more likely to be hospitalised to offer urgent care and schedule appointments in primary care clinics. In addition, health care plans could be formulated to improve elder primary care, decrease overcrowding in emergency centers, and decrease elder healthcare costs in the future. ^