Improving sensitivity of oral fluid testing in IgG prevalence studies: application of mixture models to a rubella antibody survey

A method for the analysis of age-stratified antibody prevalence surveys is applied to a previously reported survey of antibody to rubella virus using oral fluid samples in which the sensitivity of the assay used was shown to be compromised. The age-specific distribution of the quantitative results of antibody tests using oral fluids is modelled as a mixture of strong positive, weak positive and negative components. This yields maximum likelihood estimates of the prevalence at each age and demonstrates that, when used in conjunction with mixture modelling techniques, the results of antibody prevalence studies using oral fluids accurately reflect those obtained using sera.     

Analysis of longitudinal bacterial carriage studies accounting for sensitivity of swabbing: an application to Neisseria meningitidis

Longitudinal carriage studies of colonizing bacteria such as Neisseria meningitidis can provide important insights into the transmission dynamics of these organisms. Carriage is detected by culturing from a nasopharyngeal swab, but the sensitivity of this technique is low and varies between studies. This paper applies a statistical method for estimating the sensitivity of swabbing, infection rate, recovery rate and initial prevalence of carriage to three longitudinal carriage studies of N. meningitidis. These parameters and 95% confidence intervals were estimated using maximum likelihood techniques. The sensitivity of swabbing was estimated to be 60-83% and this should be taken into account when interpreting carriage studies. The estimates of force of infection and recovery rates seem to be consistent with estimates from more traditional methods. Differences in the parameter estimates between datasets may be due to differences in study design. This method could be used to assist in the design of future carriage studies.     

A meta-analysis of nocturnal noninvasive positive pressure ventilation in patients with stable COPD

STUDY OBJECTIVES: The potential benefits of noninvasive positive pressure ventilation (NIPPV) for patients with COPD remains inconclusive, as most studies have included only a small number of patients. We therefore undertook a meta-analysis of randomized controlled trials (RCTs) that compared nocturnal NIPPV with conventional management in patients with COPD and stable respiratory failure. DESIGN: RCTs were identified from several sources, such as MEDLINE, EMBASE, and CINAHL. In addition, records were identified through hand searching of abstracts from meetings of the American Thoracic Society, the American College of Chest Physicians, and the European Respiratory Society. PATIENTS: Patients with COPD according to the definition of the American Thoracic Society. INTERVENTIONS: NIPPV applied via a nasal or facemask for at least 5 h/d for at least 3 weeks. Patients in the actively treated group continued to receive the usual management for COPD. The control group received the same management as the study group but did not receive NIPPV. Measurements and results: PaCO(2), PaO(2), 6-min walking distance (6MWD), respiratory muscle function, FEV(1), vital capacity, and sleep efficiency (time asleep as a percentage of total time in bed) were used as outcome measures. The publications were reduced to 10 potentially eligible articles from 164 publications retrieved from computer searches and 8 further abstracts. Four trials were finally included in the meta-analysis. The only outcome for which the confidence intervals excluded zero was maximal inspiratory pressure (PImax). The confidence intervals for the other outcomes included zero. The mean treatment effects for FEV(1) and PImax were small, whereas it was moderate for the 6MWD. Small negative effects were found for the outcomes of vital capacity, PaCO(2), and sleep efficiency. CONCLUSIONS: This meta-analysis of 3 months of NIPPV in patients with stable COPD showed that ventilatory support did not improve lung function, gas exchange, or sleep efficiency. The high upper limit of the confidence interval for the 6MWD suggested that some people do improve their walking distance. The small overall sample size precluded a clear clinical direction regarding the effects of NIPPV in patients with COPD.     

Functional magnetic resonance imaging of source versus item memory

Both the frontal lobes and the medial temporal lobe (particularly the hippocampus) have been implicated in encoding and retrieval of episodic memory information. We report an experiment that manipulates whether source information, item information, or both are required at retrieval. Two sources were used in a factorial design in which the main effect of source and item retrieval, along with their interaction, could be measured by fMRI activations. When source information was required at retrieval the left frontal lobe showed significant activation but not when item retrieval was required. Hippocampal activation showed no difference between source and item retrieval. This pattern of results supports a model proposing a larger role for the frontal lobes in encoding and retrieval of source information.     

Socioeconomic status and dissatisfaction with health care among chronically ill African Americans

Addressing differences in social class is critical to an examination of racial disparities in health care. Low socioeconomic status is an important determinant of access to health care. Results from a qualitative, in-depth interview study of 60 African Americans who had one or more chronic illnesses found that low-income respondents expressed much greater dissatisfaction with health care than did middle-income respondents. Low socioeconomic status has potentially deadly consequences for several reasons: its associations with other determinants of health status, its relationship to health insurance or the absence thereof, and the constraints on care at sites serving people who have low incomes.     

When we "are neither alive nor dead": the Schiavo's case

Recently the world was drawn into the news of the Terri Schiavo case. Like in that case many other patients and relatives face similar situation. We foresee more medical and legal struggles caused primarily by the use of advanced life-sustaining medical technology that could prolong the life of human beings with progressive neurodegenerative disorders, or acquired irreversible brain injury. This is an appropriate time to ponder the course of action when we "neither live nor die". We agree, as Terri Schiavo's parents' representatives affirm, that Terri was not in a terminal state (end-of-life situation). Her life could have been prolonged for another fifteen years. However, her clinical presentation was not easy to comprehend by some. That way Terri has become a window through which the educated public realized that ethical decisions regarding medical affairs are always played in an environment of uncertainty and probabilities. One of the factors that make such situation more painful is the patient's incompetence to respond. In the long run, despite the family tragedy, we can not deny that the Schiavo case provides us the basis for a thorough and careful reflection about our human brittleness.