Estimating adjusted prevalence ratio in clustered cross-sectional epidemiological data

BACKGROUND: Many epidemiologic studies report the odds ratio as a measure of association for cross-sectional studies with common outcomes. In such cases, the prevalence ratios may not be inferred from the estimated odds ratios. This paper overviews the most commonly used procedures to obtain adjusted prevalence ratios and extends the discussion to the analysis of clustered cross-sectional studies. METHODS: Prevalence ratios(PR) were estimated using logistic models with random effects. Their 95% confidence intervals were obtained using delta method and clustered bootstrap. The performance of these approaches was evaluated through simulation studies. Using data from two studies with health-related outcomes in children, we discuss the interpretation of the measures of association and their implications. RESULTS: The results from data analysis highlighted major differences between estimated OR and PR. Results from simulation studies indicate an improved performance of delta method compared to bootstrap when there are small number of clusters. CONCLUSION: We recommend the use of logistic model with random effects for analysis of clustered data. The choice of method to estimate confidence intervals for PR (delta or bootstrap method) should be based on study design

Viral dynamics and pharmacokinetics of peginterferon alpha-2a and peginterferon alpha-2b in naive patients with chronic hepatitis C:a randomized,controlled study study

The two available pegylated interferon formulations, peginterferon alpha-2a and peginterferon alpha-2b, have different pharmacokinetic profiles; as a result they may have differing abilities to suppress the hepatitis C virus. A recently reported study by Formann and colleagues assessing early viral kinetics among 20 patients receiving peginterferon alpha-2b either once or twice weekly suggests that once-weekly administration of peginterferon alpha-2b is not sufficient for continuous exposure to interferon over 160 h. Twice-weekly administration is recommended to avoid increases in viral load as interferon levels decline prior to the end of the one-week dosing period. The objective of this study was to compare viral dynamics and pharmacokinetics between peginterferon alpha-2a and peginterferon alpha-2b in interferon-naive chronic hepatitis C patients. Patients were randomized to receive peginterferon alpha- 2a 180 μg (n=10) or peginterferon alpha-2b 1.0 μg/kg (n=12) once weekly. Serum peginterferon concentrations were measured at baseline, 24, 48, 120 and 168 h. Hepatitis C virus (HCV) RNA was measured at baseline, 24, 48, 120 and 168 h during week 1 and then at 4 and 12 weeks. Peginterferon alpha-2b achieved maximal serum levels at 24 h, and then decreased rapidly. Of the 12 patients who received peginterferon alpha-2b, no drug was detectable in seven (58%) patients at 120 h and in 11 (92%) at 168 h. In contrast, peginterferon alpha-2a concentrations increased continuously over time, reaching maximal serum levels from 48 to 168 h. Drug was detectable in all 10 patients at 168 h. At weeks 1 and 4 no significant difference was observed in mean HCV RNA between the groups. However, at week 12, mean HCV RNA was significantly lower in the peginterferon alpha-2a group versus the peginterferon alpha-2b group (2.8126 vs 3.8726; P<0.01). The differences in mean HCV RNA values at 12 weeks may be related to the different absorption and distribution profiles of the two drugs. In conclusion, once-weekly administration of peginterferon alpha-2b (1.0 μg/kg/wk) may be insufficient for continuous interferon exposure; twice-weekly administration may help avoid increases in viral replication as interferon levels decline. Larger-scale studies assessing both viral kinetics and sustained virological responses are needed to confirm these observations

Area-under-the-curve for peginterferon alpha-2a and peginterferon alpha-2b is not related to body weight in treatment-naive patients with chronic hepatitis C

Abstract: One reason for dosing a drug by body weight is to reduce interpatient variability in clinical response. This study evaluated the relationship between body weight and drug exposure for peginterferon alpha-2a and peginterferon alpha-2b used in combination with ribavirin for treating patients with chronic hepatitis C. These two products are dosed differently: peginterferon alpha-2a is flat-dosed at 180 mu g regardless of body weight, whereas peginterferon alpha-2b is dosed by body weight at 0.5-1.5 mu g/kg. Bodyweight dosing of peginterferon alpha-2b is purported to overcome the adverse effect of increased body weight on sustained virological response. To test this hypothesis, we measured the area-under-the-curve (AUC) for both drugs as part of a previously reported pharmacokinetics study. In total, 22 interferon- naive patients with chronic hepatitis C were treated for 12 weeks. Patients were randomly assigned in a 1:1 ratio to receive once-weekly peginterferon alpha-2a 180 mu g (n=10)or peginterferon alpha-2b 1.0 mu g/kg (n=1 2). Ribavirin was dosed by body weight at 1000mg/day ( 75 kg). We found no correlation between body weight and AUC for either peginterferon alpha-2a or peginterferon alpha-2b. Considerable interpatient variability in AUC occurred for peginterferon alpha-2a [coefficient of variation (CV): 37.5%] and, despite dosing by body weight, for peginterferon alpha-2b (CV: 36.8%). Thus, there appears to be no rationale for a body-weight dosing regimen for peginterferon alpha-2a, and such dosing does not achieve more consistent AUC measurements in patients receiving peginterferon alpha-2

Predictors of knowledge of H1N1 infection and transmission in the U.S. population

<p>Abstract</p> <p>Background</p> <p>The strength of a society’s response to a public health emergency depends partly on meeting the needs of all segments of the population, especially those who are most vulnerable and subject to greatest adversity. Since the early stages of the H1N1 pandemic, public communication of H1N1 information has been recognized as a challenging issue. Public communication is considered a critical public health task to mitigating adverse population health outcomes before, during, and after public health emergencies. To investigate knowledge and knowledge gaps in the general population regarding the H1N1 pandemic, and to identify the social determinants associated with those gaps, we conducted a survey in March 2010 using a representative random sample of U.S. households.</p> <p>Methods</p> <p>Data were gathered from 1,569 respondents (66.3% response rate) and analyzed using ordered logistic regression to study the impact of socioeconomic factors and demographic characteristics on the individual’s knowledge concerning H1N1 infection and transmission.</p> <p>Results</p> <p>Results suggest that level of education and home ownership, reliable indicators of socioeconomic position (SEP), were associated with knowledge of H1N1. Level of education was found to be directly associated with level of knowledge about virus transmission [OR = 1.35, 95% C.I. 1.12-1.63]. Home ownership versus renting was also positively associated with knowledge on the signs and symptoms of H1N1 infection in particular [OR = 2.89, 95% C.I. 1.26-6.66].</p> <p>Conclusions</p> <p>Policymakers and public health practitioners should take specific SEP factors into consideration when implementing educational and preventive interventions promoting the health and preparedness of the population, and when designing communication campaigns during a public health emergency.</p

A health behaviour cross-sectional study of immigrants and non-immigrants in a Swiss urban general-practice setting.

BACKGROUND: Little is known about smoking, unhealthy use of alcohol, and risk behaviours for sexually transmitted diseases (STDs) in immigrants from developed and developing countries. METHOD: We performed a cross-sectional study of 400 patients who consulted an academic emergency care centre at a Swiss university hospital. The odds ratios for having one or more risk behaviours were adjusted for age, gender, and education level. RESULTS: Immigrants from developing countries were less likely to use alcohol in an unhealthy manner (OR = 0.35, 95% CI 0.22-0.57) or practise risk behaviours for STDs (OR = 0.31, 95% CI 0.13-0.74). They were also less likely to have any of the three studied risk behaviours (OR = 2.5, 95% CI 1.5-4.3). DISCUSSION: In addition to the usual determinants, health behaviours are also associated with origin; distinguishing between immigrants from developing and developed countries is useful in clinical settings. Surprisingly, patients from developing countries tend to possess several protective characteristics