Association between lead source exposure and blood lead levels in some lead manufacturing countries: A systematic review and meta-analysis.

Lead is one of the 10 most toxic chemicals of greatest concern for its effects on public health. Predominantly, in undeveloped countries, high blood lead levels (BLLs) persist in the population. To develop intervention strategies that may reduce lead exposure in populations, it is a priority to know the sources of lead pollution. The objective of this critical review and meta-analysis is to assess whether there is an association between different sources of lead exposure and the mean difference in blood lead levels in people exposed. To identify the major lead source exposure, a statistical analysis was performed on selection studies. This investigation reveals the limited information available on the sources of lead in Mexico and other lead producer countries, such as Croatia, Ecuador, Brazil, South Korea, India, Nigeria, Turkey, and China. Meta-analysis could be performed only in battery, smelting mining, and glazed ceramic workers. Battery manufacturing workers have the highest mean difference level of lead in their blood worldwide. Mexico has the second highest mean difference BLL in battery workers in the world. An interesting difference between the mean difference in BLL in mining workers from uncontrolled industry (-39.38) and controlled industry (-5.68) was found. This difference highlighted the success of applying strict control of lead sources and community education to reduce BLL and its potential harmful effects on human health and the environment. Children living near mining sites have the highest mean difference BLL (-11.1). This analysis may aid in assessing the source of lead exposure associated with a range of BLLs in people. Furthermore, this review highlights several social and cultural patterns associated with lead exposure and lead levels in control populations. These results could help to develop international lead regulations and appropriate public health guidelines to protect people around the world.

[Statistical methods for effect size analysis]. / Métodos estadísticos para el análisis del tamaño del efecto.

Informing in the studies about the effect size of an intervention or the impact of the factor(s) about an outcome, allows better decision-making for the application of the results in clinical practice. This article presents different methods to analyze the effect size, which can be through direct or indirect statistical methods. Within the direct methods, there's the difference in means between groups and the difference of absolute or relative frequencies. Among the indirect methods, Cohen's "d" family (which are based on standard deviation values), the "r and R2" family, measures of association (e.g. OR, RR, HR), and impact measures (e.g. NNT) are shown. The decision to use any of these methods depends on the objectives of the study and the measuring scale that is used to assess the results, as well as the data distribution. In order to enhance the understanding of the methods described in this article, examples are included, and the need to include level of precision (e.g. confidence intervals) is highlighted, along with the clinical decision thresholds for a better interpretation.

Informar en los estudios sobre el tamaño del efecto de una intervención o del impacto de factor(es) sobre un desenlace, permite tomar mejores decisiones para la aplicación de los resultados a la práctica clínica. En este artículo se presenta la manera de analizar el tamaño del efecto, lo cual puede ser mediante métodos estadísticos directos o indirectos. Dentro de los métodos directos, se encuentra la diferencia de promedios entre grupos y la diferencia de frecuencias absolutas o relativas. Dentro de los métodos indirectos se muestran los índices de la familia de "d" de Cohen (que se basan en valores de desviación estándar), la familia de "r y R2", medidas de asociación (RM, RR, HR) e impacto (NNT). La decisión del uso de cualquiera de los métodos descritos, depende de los objetivos del estudio, la escala de medición usada para evaluar los resultados y la distribución de los datos. Para facilitar la comprensión, se incluyen ejemplos y se resalta la necesidad de incluir los diferentes estadísticos con su nivel de precisión (ej. intervalos de confianza), junto con los umbrales clínicos de decisión, a fin de mejorar su interpretación.

Subcutaneous allergen immunotherapy for asthma: A randomized, double-blind, placebo-controlled study with a standardized Blomia tropicalis vaccine.

BACKGROUND: Sensitization to Blomia tropicalis (Bt) is very frequent in the tropics, and particularly in Cuba, being a significant cause of allergic asthma. Allergen immunotherapy (AIT) with Bt can be a therapeutic option, however, placebo-controlled clinical trials have not been reported. OBJECTIVE: To assess the therapeutic effect and safety of AIT for asthma using a standardized allergen vaccine of B. tropicalis by subcutaneous route, in allergic asthmatic patients exposed and sensitized to this mite species. METHODS: A double-blind, placebo-controlled Phase II trial was conducted in 35 adults (18 with treatment and 17 with placebo), with mild to moderate asthma, predominantly sensitized to Bt. AIT was administered subcutaneously in increasing doses from 4 to 6000 Biological Units using a locally manufactured standardized extract (BIOCEN, Cuba). Patient assessment was performed using symptom-medication score (SMS), peak expiratory flow and skin reactivity relative to Histamine as measured by skin prick test (SPT). RESULTS: The 12-month treatment achieved a significant (p < 0.001) decrease of SMS. Symptom score showed only 41% (CI: 26-61) of placebo values, whereas medication was 34.5% (22.4%-63.3%). Treatment was regarded clinically effective in 67% of patients (OR 32; 95%CI: 17 to 102). The effect size on symptoms and medication was higher than has been reported with equivalent allergen dosages of D. pteronyssinus and D. siboney in Cuban asthmatic patients. Skin reactivity to Bt was also significantly reduced (p = 0.0001), increasing 148-fold the allergen threshold to elicit a positive skin test. This desensitization effect was specific to Bt and did not modify the reactivity to Dermatophagoides. The change of specific skin reactivity was significantly (p < 0.05) correlated to clinical improvement. All adverse events were local with a frequency of 2.4% of injections. CONCLUSIONS: Subcutaneous AIT with Blomia tropicalis was effective and safe in asthmatic adults exposed and sensitized to this mite species in a tropical environment. TRIAL REGISTRATION: Cuban Public Registry of Clinical Trials: RPCEC00000026 (WHO International Clinical Trial Registry Platform ICTRP).

Trends in Iron, Zinc, and Vitamin A Status Biomarkers Among Colombian Children: Results From 2 Nationally Representative Surveys.

BACKGROUND: Micronutrient deficiencies are still highly prevalent in countries undergoing the nutrition transition, but nationally representative data documenting their burden in children are exceedingly rare. OBJECTIVE: To examine the distribution and recent trends in micronutrient status biomarkers of Colombian children. METHODS: We compared the distributions of plasma ferritin, serum zinc, and vitamin A in Colombian children between 2005 and 2010 using 2 cross-sectional, nationally representative surveys overall and by categories of sociodemographic variables. Analysis for ferritin included boys and nonpregnant girls aged 1 to 17 years. Analyses for zinc and vitamin A included children aged 1 to 4 years. RESULTS: The mean 2010 to 2005 differences in ferritin, zinc, and vitamin A were 2.5 µg/L (95% confidence interval [CI]: 1.3 to 3.7), -34.9 µg/dL (95% CI: -39.6 to -30.2), and -11.5 µg/dL (95% CI: -12.3 to -10.7), respectively, after adjusting for sociodemographic characteristics. These differences varied significantly by region of residence. In 2010, region of residence was a significant correlate for all 3 micronutrients. Other important correlates included age and maternal education for ferritin and body mass index-for-age Z score, maternal education, wealth index, food insecurity, and urbanicity for vitamin A. CONCLUSIONS: Plasma ferritin was slightly higher in 2010 than in 2005, whereas serum zinc and vitamin A were substantially lower in 2010. In the absence of obvious causal explanations, it is uncertain whether this decline represents a worsening of micronutrient status in Colombian children or an artifact due to systematic laboratory or data management errors incurred in the surveys.

Different digestion enzymes used for human pancreatic islet isolation: a mixed treatment comparison (MTC) meta-analysis.

Collagenases are critical reagents determining yield and quality of isolated human pancreatic islets and may affect islet transplantation outcome. Some islet transplantation centers have compared 2 or more collagenase blends; however, the results regarding differences in quantity and quality of islets are conflicting. Thus, for the first time, a mixed treatment comparison (MTC) meta-analysis was carried out to compile data about the effect of different collagenases used for human pancreas digestion on islet yield, purity, viability and stimulation index (SI). Pubmed, Embase and Cochrane libraries were searched. Of 755 articles retrieved, a total of 15 articles fulfilled the eligibility criteria and were included in the MTC meta-analysis. Our results revealed that Vitacyte and Liberase MTF were associated with a small increase in islet yield (islet equivalent number/g pancreas) when compared with Sevac enzyme [standardized mean difference (95% credible interval - CrI) = -2.19 (-4.25 to -0.21) and -2.28 (-4.49 to -0.23), respectively]. However, all other enzyme comparisons did not show any significant difference regarding islet yield. Purity and viability percentages were not significantly different among any of the analyzed digestion enzymes. Interestingly, Vitacyte and Serva NB1 were associated with increased SI when compared with Liberase MTF enzyme [unstandardized weighted mean difference (95% CrI) = -1.69 (-2.87 to -0.51) and -1.07 (-1.79 to -0.39), respectively]. In conclusion, our MTC meta-analysis suggests that the digestion enzymes currently being used for islet isolation works with similar efficiency regarding islet yield, purity and viability; however, Vitacyte and Serva NB1 enzymes seem to be associated with an improved SI as compared with Liberase MTF.

Daily vs. intermittent inhaled corticosteroids for recurrent wheezing and mild persistent asthma: a systematic review with meta-analysis.

BACKGROUND: Intermittent ICS treatment with SABA in response to symptoms, is an emerging strategy for control of mild-to-moderate asthma, and recurrent wheezing. This systematic revue compares the efficacy of daily vs. intermittent ICS among preschoolers, children and adults with persistent wheezing and mild to moderate stable persistent asthma. METHODS: Systematic review of randomized, placebo-controlled trials with a minimum of 8 weeks of daily (daily ICS with rescue SABA during exacerbations) vs. intermittent ICS (ICS plus SABA at the onset of symptoms), were retrieved through different databases. Primary outcome was asthma exacerbations; secondary outcomes were pulmonary function tests, symptoms, days without symptoms, SABA use, corticosteroids use, days without rescue medication use, expired nitric oxide and serious adverse events. RESULTS: Seven trials (1367 participants) met inclusion criteria there was no statistically significant difference in the rate of asthma exacerbations between those with daily vs. intermittent ICS (0.96; 95% CI: 0.86, 1.06, I(2) = 0%). In the sub-group analysis, no differences were seen in duration of studies, step-up strategy or age. However, compared to intermittent ICS, the daily ICS group had a significant increase in asthma-free days and non-significant decreases in rescue SABA use and exhaled nitric oxide measurement. CONCLUSIONS: No significant differences between daily and intermittent ICS in reducing the incidence of asthma exacerbations was found. However, the daily ICS strategy was superior in many secondary outcomes. Therefore, this study suggests to not change daily for intermittent ICS use among preschoolers, children with persistent wheezing and adults with mild-to-moderate stable persistent asthma. International prospective register of systematic reviews http://www.crd.york.ac.uk/PROSPERO/ (CRD42012003228).