Analysis of Multiply Matched Retrospective Studies When Risk Factor Under Study is Discrete,With Two or More Levels

The odds ratio is known to closely approximate the relative risk when the disease is rare. Logistic regression models are often used to estimate such odds ratios, but here a different model is used which avoids the assumptions implicit in logistic modelling; it also has the advantage of providing a test of homogeneity for odds rat os in situations where the logistic model cannot.     

Climate‐driven spatial mismatches between British orchards and their pollinators: increased risks of pollination deficits

Understanding how climate change can affect crop‐pollinator systems helps predict potential geographical mismatches between a crop and its pollinators, and therefore identify areas vulnerable to loss of pollination services. We examined the distribution of orchard species (apples, pears, plums and other top fruits) and their pollinators in Great Britain, for present and future climatic conditions projected for 2050 under the SRES A1B Emissions Scenario. We used a relative index of pollinator availability as a proxy for pollination service. At present, there is a large spatial overlap between orchards and their pollinators, but predictions for 2050 revealed that the most suitable areas for orchards corresponded to low pollinator availability. However, we found that pollinator availability may persist in areas currently used for fruit production, which are predicted to provide suboptimal environmental suitability for orchard species in the future. Our results may be used to identify mitigation options to safeguard orchard production against the risk of pollination failure in Great Britain over the next 50 years; for instance, choosing fruit tree varieties that are adapted to future climatic conditions, or boosting wild pollinators through improving landscape resources. Our approach can be readily applied to other regions and crop systems, and expanded to include different climatic scenarios.     

Potential impacts of water hyacinth invasion and management on water quality and human health in Lake Tana watershed,Northwest Ethiopia

Incursion of water hyacinth, Eichhornia crassipes, has been a potential threat to Lake Tana and its ecosystem services. Its expansion is currently managed by abstraction (removing by hand); nonetheless, the disposal of mats and formation of pools are remaining problematic. This study aimed to assess the potential effects of water hyacinth and its management on water quality and human health. Biotic and abiotic data were collected on open water, water hyacinth covered and water hyacinth cleared out habitats. A total of 3673 invertebrates belonging to twenty-one families were collected from 45 sites. Culicidae was the most abundant family accounting (37.2%), followed by Unionoidae (19.4%) and Sphaeriidae (8.1%). Abundance of anopheline and culicine larvae were significantly higher in water hyacinth cleared out habitats (p?<?0.05). Water conductivity and total dissolved solids were significantly higher in habitats covered with water hyacinth (p?<?0.05). In conclusion, water hyacinth infestation had a negative impact on water quality and biotic communities. The physical abstraction of water hyacinth provided a very good habitat for the proliferation of mosquito larvae. Therefore, integrating water hyacinth management practices along with mosquito larvae control strategy could help to abate the potential risk of malaria outbreak in the region. In addition, developing watershed scale nutrient management systems could have a vital contribution for managing water hyacinth invasion in the study area.     

Na+, K+ and Cl− selectivity of the permeability pathways induced through sterol-containing membrane vesicles by amphotericin B and other polyene antibiotics

Membrane diffusion potentials induced by amphotericin B (AmB), amphotericin B methyl ester (AmE), N-fructosyl AmB (N FruAmB) and vacidin, an aromatic polyene antibiotic, in ergosterol- or cholesterol-containing egg yolk phosphatidylcholine large unilamellar vesicles (LUV), were measured in various media, in order to determine the relative selectivity of Na⁺, K⁺, Cl^– and other ions in these environments. Changes in the membrane potential were followed by fluorescence changes of 3,3-dipropylthiadicarbocyanine (diS-C₃-(5)). Subtle changes in intercationic selectivity were monitored by measuring biionic potentials, using the fluorescent pH sensitive probe pyranine. In all the cases studied, the intereationic selectivity of the permeability pathways induced by the four antibiotics was weak compared to that of specific biological channels, though distinct differences were noted. With AmB the selectivity appeared to be concentration dependent. Above 5 × 10^–7 M, the sequence determined for sterol-free small unilamellar vesicles (SUV) and cholesterol-containing SUV and LUV, Na⁺ > K⁺ > Rb⁺ Cs⁺ > Li⁺ (sulfate salts), corresponded closely to Eisenman selectivity sequence number VII. At 5 × 10^–7 M and below the selectivity switched from Na⁺ > K⁺ to K⁺ > Na ⁺. In contrast, Li⁺ was the most permeant ion for AmB channels in the presence of ergosterol. The selectivity between Na⁺ or K⁺ vs. Cl^– varied with the antibiotic. It was very strong with vacidin at concentrations below 5 × 10^–7 M, smaller with AmB, nil with AmE and N FruAmB. The selectivities observed were antibiotic, concentration and time de pendent, which confirms the existence of different types of channels.Abbreviations AmB amphotericin B - AmE amphotericin B methylester - BLM bilayer membranes - DiSC₃(5) 3,3-dipropylthi-acarbocyanine iodide - DMSO dimethylsulfoxide - EPC egg yolk lecithin - FCCP carbonyl cyanide p-trifluoro methoxyphenyl-hydrazone - HEPES N-(2-hydroxyethylpiperazine)-N-(2-ethanesulfonic acid) - LUV large unilamellar vesicles - MOPS 3-(N-morpholino)propanesulfonic acid - N-Fru AmB N(1-deoxy-D-fructos-1-yl) amphotericin B - Oxonol V1 bis(3-propyl-5-oxoisoazol-4yl)pentamethine oxonol - SUV small unilamellar vesicles     

Estimation of Relative Risk Under M to R Matching

Estimation of the relative risk from a rare disease is carried out using M:R matching. Both conditional and unconditional likelihood methods are used, leading in each case to the same estimate; a non-iterative estimate is always available under M:R matching, M ≦2. The method also enables the testing of homogeneity even when information on the matching variate is unavailable and this is an advantage over logistic regression methods.     

Estimation of Relative Risk Under Variable Multiple Matching

When disease incidence is low, the odds ratio, which closely approximates relative risk, is estimated optimally in a closed form using a variable matching ratio in a retrospective design. The model also enables one to assess the homogeneity of the odds ratio from the same one matched sample. Analogous procedures are shown to hold for the prospective design.     

Predictors of HIV Testing among Patients with Tuberculosis in North West Ethiopia: A Case-Control Study

Background

The acceptance of HIV testing among patients with tuberculosis (TB) is low in Ethiopia. The purpose of this study was to assess predictors of acceptance of HIV testing among patients with TB in North Ethiopia.

Methods

A case control study was conducted in eight randomly selected health facilities in North Ethiopia from February 5 to March 11, 2009. A total of 282 participants (188 controls and 94 cases) were included in the study. Cases were TB patients who refused to be tested for HIV. We used quantitative and qualitative methods of data collection. For the quantitative survey, cases and controls were interviewed by trained nurses using a pre-tested and structured questionnaire. In-depth interviews were conducted with 5 nurse counselors and 15 TB patients. Bivariate and multivariate analysis was done using SPSS 16.0 statistical software.

Results

The uptake of HIV testing among TB patients in the study health facilities was 70.6%. The rate of TB/HIV co-infection in those who were tested was 36.2%. From the source population, a total of 282 participants were included in the study. TB patients who had formal education [OR = 2.35, (95%CI: 1.33, 4.13)], high awareness about the benefits of HIV counseling and testing [OR = 3.14, 95%CI: 1.77, 5.50)], and a low stigmatized attitude [OR = 3.16, 95%CI: 1.79, 5.59)] were more likely to accept HIV testing. The qualitative study also revealed that low awareness and stigma were the major reasons for non-acceptance of HIV testing.

Conclusion

“Knowledge and attitude” factors were the major barriers for HIV testing. Tailored training should be given to TB patients and the community concerning the benefits of HIV testing. During counseling sessions, health workers should focus on barriers of uptake of HIV testing such as stigma and discrimination.     

Prelacteal feeding and associated factors in Ethiopia: systematic review and meta-analysis

Background

Prelacteal feeding can be defined as giving any solid or liquid foods other than breast milk during the first three days after birth. It affects timely initiation of breastfeeding and exclusive breastfeeding practices. Even though the issue was investigated in Ethiopia, fragmented and inconsistent findings were reported. Therefore, the main objective of this meta-analysis was to estimate the pooled prevalence of prelacteal feeding and associated factors in Ethiopia.

Methods

The preferred reporting items for systematic reviews and meta-analyses guideline was followed. Articles were systematically searched through different searching mechanisms. Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument adapted for cross-sectional study design was used for quality assessment of each individual study. The total of 28 studies were included and analyzed. The random effect model was used to estimate the pooled prevalence; subgroup analysis and meta-regression were performed to identify the probable source of heterogeneity. Both Egger’s, and Begg’s test were used to check publication bias. The effects between associated factor variables, and prelacteal feeding practices were tested.

Results

A total of 492 studies were retrieved and 28 studies were included in the meta-analysis. The pooled prevalence of prelacteal feeding practice in Ethiopia was 25.29% (95% Confidence Interval [CI] 17.43, 33.15) with severe heterogeneity (I² =?99.7, p <?0.001) and no publication bias. Antenatal care (Odds Ratio [OR] 0.25, 95% CI 0.09, 0.69), counselling on infant feeding (OR 0.37, 95% CI 0.22, 0.63), timely initiation of breastfeeding (OR 0.28, 95% CI 0.21, 0.38) and an urban residence (OR 0.47, 95% CI 0.26, 0.86) had lower odds, while home birth had higher odds (OR 3.93, 95% CI 2.17, 7.10) of prelacteal feeding in Ethiopia.

Conclusions

In Ethiopia, one in four children were given prelacteal foods. Mothers who gave birth at home are more prone to give prelacteal foods. Whereas, antenatal care, timely initiation of breastfeeding, counseling on infant feeding and an urban residence decreases prelacteal feeding practices in Ethiopia. Therefore, the government and health institutions should focus to increase maternal health service utilization and promote infant and young child feeding practices according to the guideline.

     

Estimation of Attributable Risk in the Presence of Confounding

LEVIN 's attributable risk due to a risk factor is estimated in the presence of confounding in the retrospective study context. The crude attributable risk is decomposed into the attributable risk due to a risk factor and a bias factor which is shown to vanish only when the confounding factor is unassociated to either the risk factor or the Disease or to both. Asymptotic tests are provided for testing interaction, and an appropriate pooled estimate is derived when constancy of partial attributable risks prevails over the levels of the confounding factor.