I Just Ran a Thousand Analyses: Benefits of Multiple Testing in Understanding Equivocal Evidence on Gene-Environment Interactions

BackgroundIn psychiatric genetics research, the volume of ambivalent findings on gene-environment interactions (G x E) is growing at an accelerating pace. In response to the surging suspicions of systematic distortion, we challenge the notion of chance capitalization as a possible contributor. Beyond qualifying multiple testing as a mere methodological issue that, if uncorrected, leads to chance capitalization, we advance towards illustrating the potential benefits of multiple tests in understanding equivocal evidence in genetics literature.MethodWe focused on the interaction between the serotonin-transporter-linked promotor region (5-HTTLPR) and childhood adversities with regard to depression. After testing 2160 interactions with all relevant measures available within the Dutch population study of adolescents TRAILS, we calculated percentages of significant (p < .05) effects for several subsets of regressions. Using chance capitalization (i.e. overall significance rate of 5% alpha and randomly distributed findings) as a competing hypothesis, we expected more significant effects in the subsets of regressions involving: 1) interview-based instead of questionnaire-based measures; 2) abuse instead of milder childhood adversities; and 3) early instead of later adversities. Furthermore, we expected equal significance percentages across 4) male and female subsamples, and 5) various genotypic models of 5-HTTLPR.ResultsWe found differences in the percentages of significant interactions among the subsets of analyses, including those regarding sex-specific subsamples and genetic modeling, but often in unexpected directions. Overall, the percentage of significant interactions was 7.9% which is only slightly above the 5% that might be expected based on chance.ConclusionTaken together, multiple testing provides a novel approach to better understand equivocal evidence on G x E, showing that methodological differences across studies are a likely reason for heterogeneity in findings - but chance capitalization is at least equally plausible.     

The In Ovo Chick Chorioallantoic Membrane (CAM) Assay as an Efficient Xenograft Model of Hepatocellular Carcinoma

The chick chorioallantoic membrane (CAM) begins to develop by day 7 after fertilization and matures by day 12. The CAM is naturally immunodeficient and highly vascularized, making it an ideal system for tumor implantation. Furthermore, the CAM contains extracellular matrix proteins such as fibronectin, laminin, collagen, integrin alpha(v)beta3, and MMP-2, making it an attractive model to study tumor invasion and metastasis. Scientists have long taken advantage of the physiology of the CAM by using it as a model of angiogenesis. More recently, the CAM assay has been modified to work as an in vivo xenograft model system for various cancers that bridges the gap between basic in vitro work and more complex animal cancer models. The CAM assay allows for the study of tumor growth, anti-tumor therapies, and pro-tumor molecular pathways in a biologically relevant system that is both cost- and time-effective. Here, we describe the development of CAM xenograft model of hepatocellular carcinoma (HCC) with embryonic survival rates of up to 93% and reliable tumor take leading to growth of three-dimensional, vascularized tumors.     

Potential Cost-Effectiveness of Prenatal Distribution of Misoprostol for Prevention of Postpartum Hemorrhage in Uganda

Background

In settings where home birth rates are high, prenatal distribution of misoprostol has been advocated as a strategy to increase access to uterotonics during the third stage of labor to prevent postpartum hemorrhage (PPH). Our objective was to project the potential cost-effectiveness of this strategy in Uganda from both governmental (the relevant payer) and modified societal perspectives.

Methods and Findings

To compare prenatal misoprostol distribution to status quo (no misoprostol distribution), we developed a decision analytic model that tracked the delivery pathways of a cohort of pregnant women from the prenatal period, labor to delivery without complications or delivery with PPH, and successful treatment or death. Delivery pathway parameters were derived from the Uganda Demographic and Health Survey. Incidence of PPH, treatment efficacy, adverse event and case fatality rates, access to misoprostol, and health resource use and cost data were obtained from published literature and supplemented with expert opinion where necessary. We computed the expected incidence of PPH, mortality, disability adjusted life years (DALYs), costs and incremental cost effectiveness ratios (ICERs). We conducted univariate and probabilistic sensitivity analyses to examine robustness of our results. In the base-case analysis, misoprostol distribution lowered the expected incidence of PPH by 1.0% (95% credibility interval (CrI): 0.55%, 1.95%), mortality by 0.08% (95% CrI: 0.04%, 0.13%) and DALYs by 0.02 (95% CrI: 0.01, 0.03). Mean costs were higher with prenatal misoprostol distribution from governmental by US$3.3 (95% CrI: 2.1, 4.2) and modified societal (by US$1.3; 95% CrI: -1.6, 2.8) perspectives. ICERs were US$191 (95% CrI: 82, 443) per DALY averted from a governmental perspective, and US$73 (95% CI: -86, 256) per DALY averted from a modified societal perspective.

Conclusions

Prenatal distribution of misoprostol is potentially cost-effective in Uganda and should be considered for national-level scale up for prevention of PPH.     

The Costs of Delivering Integrated HIV and Sexual Reproductive Health Services in Limited Resource Settings

Objective

To present evidence on the total costs and unit costs of delivering six integrated sexual reproductive health and HIV services in a high and medium HIV prevalence setting, in order to support policy makers and planners scaling up these essential services.

Design

A retrospective facility based costing study conducted in 40 non-government organization and public health facilities in Kenya and Swaziland.

Methods

Economic and financial costs were collected retrospectively for the year 2010/11, from each study site with an aim to estimate the cost per visit of six integrated HIV and SRH services. A full cost analysis using a combination of bottom-up and step-down costing methods was conducted from the health provider’s perspective. The main unit of analysis is the economic unit cost per visit for each service. Costs are converted to 2013 International dollars.

Results

The mean cost per visit for the HIV/SRH services ranged from $Int 14.23 (PNC visit) to $Int 74.21 (HIV treatment visit). We found considerable variation in the unit costs per visit across settings with family planning services exhibiting the least variation ($Int 6.71-52.24) and STI treatment and HIV treatment visits exhibiting the highest variation in unit cost ranging from ($Int 5.44-281.85) and ($Int 0.83-314.95), respectively. Unit costs of visits were driven by fixed costs while variability in visit costs across facilities was explained mainly by technology used and service maturity.

Conclusion

For all services, variability in unit costs and cost components suggest that potential exists to reduce costs through better use of both human and capital resources, despite the high proportion of expenditure on drugs and medical supplies. Further work is required to explore the key drivers of efficiency and interventions that may facilitate efficiency improvements.     

Relation between Intensity of Biocide Practice and Residues of Anticoagulant Rodenticides in Red Foxes (Vulpes vulpes)

Anticoagulant rodenticides (ARs) are commonly used to control rodent infestations for biocidal and plant protection purposes. This can lead to AR exposure of non-target small mammals and their predators, which is known from several regions of the world. However, drivers of exposure variation are usually not known. To identify environmental drivers of AR exposure in non-targets we analyzed 331 liver samples of red foxes (Vulpes vulpes) for residues of eight ARs and used local parameters (percentage of urban area and livestock density) to test for associations to residue occurrence. 59.8% of samples collected across Germany contained at least one rodenticide, in 20.2% of cases at levels at which biological effects are suspected. Second generation anticoagulants (mainly brodifacoum and bromadiolone) occurred more often than first generation anticoagulants. Local livestock density and the percentage of urban area were good indicators for AR residue occurrence. There was a positive association between pooled ARs and brodifacoum occurrence with livestock density as well as of pooled ARs, brodifacoum and difenacoum occurrence with the percentage of urban area on administrative district level. Pig holding drove associations of livestock density to AR residue occurrence in foxes. Therefore, risk mitigation strategies should focus on areas of high pig density and on highly urbanized areas to minimize non-target risk.     

Experienced and Perceived Risks of Mycobacterial Diseases: A Cross Sectional Study among Agropastoral Communities in Northern Tanzania

Objective

The current study was conducted to assess experienced risk factors and perceptions of mycobacterial diseases in communities in northern Tanzania.

Methods

We conducted a cross-sectional study in Arusha and Manyara regions in Northern Tanzania. We enrolled tuberculosis (TB) patients attending Mount Meru Hospital, Enduleni Hospital and Haydom Lutheran Hospitals in Arusha municipality, Ngorongoro and Mbulu districts, respectively. Patient addresses were recorded during their first visit to the hospitals. Patients with confirmed diagnosis of TB by sputum smear microscopy and/or culture at central laboratory were followed up and interviewed using pre-tested questionnaires, and selected relatives and neighbors were also interviewed. The study was conducted between June 2011 and May 2013.

Results

The study involved 164 respondents: 41(25%) were TB patients, 68(41.5%) were their relatives and 55(33.5%) their neighbors. Sixty four (39%) knew a risk factor for mycobacterial disease. Overall, 64(39%) perceived to be at risk of mycobacterial diseases. Exposure to potential risks of mycobacterial diseases were: keeping livestock, not boiling drinking water, large family, smoking and sharing dwelling with TB patients. Rural dwellers were more often livestock keepers (p<0.01), more often shared dwelling with livestock (p<0.01) than urban dwellers. More primary school leavers reported sharing dwelling with TB patients than participants with secondary and higher education (p = 0.01).

Conclusion

Livestock keeping, sharing dwelling with livestock, sharing household with a TB patient were perceived risk factors for mycobacterial diseases and the participants were exposed to some of these risk factors. Improving knowledge about the risk factors may protect them from these serious diseases.     

Xenotransplantation of Human Cardiomyocyte Progenitor Cells Does Not Improve Cardiac Function in a Porcine Model of Chronic Ischemic Heart Failure. Results from a Randomized,Blinded, Placebo Controlled Trial

Background

Recently cardiomyocyte progenitor cells (CMPCs) were successfully isolated from fetal and adult human hearts. Direct intramyocardial injection of human CMPCs (hCMPCs) in experimental mouse models of acute myocardial infarction significantly improved cardiac function compared to controls.

Aim

Here, our aim was to investigate whether xenotransplantation via intracoronary infusion of fetal hCMPCs in a pig model of chronic myocardial infarction is safe and efficacious, in view of translation purposes.

Methods & Results

We performed a randomized, blinded, placebo controlled trial. Four weeks after ischemia/reperfusion injury by 90 minutes of percutaneous left anterior descending artery occlusion, pigs (n = 16, 68.5 ± 5.4 kg) received intracoronary infusion of 10 million fetal hCMPCs or placebo. All animals were immunosuppressed by cyclosporin (CsA). Four weeks after infusion, endpoint analysis by MRI displayed no difference in left ventricular ejection fraction, left ventricular end diastolic and left ventricular end systolic volumes between both groups. Serial pressure volume (PV-)loop and echocardiography showed no differences in functional parameters between groups at any timepoint. Infarct size at follow-up, measured by late gadolinium enhancement MRI showed no difference between groups. Intracoronary pressure and flow measurements showed no signs of coronary obstruction 30 minutes after cell infusion. No premature death occurred in cell treated animals.

Conclusion

Xenotransplantation via intracoronary infusion of hCMPCs is feasible and safe, but not associated with improved left ventricular performance and infarct size compared to placebo in a porcine model of chronic myocardial infarction.     

Antepartum Membrane Stripping in GBS Carriers,Is It Safe? (The STRIP-G Study)

Objective

Stripping of the membranes is an established and widely utilized obstetric procedure associated with higher spontaneous vaginal delivery rates, reduced need for formal induction of labor and a lower likelihood of post-term pregnancy. Due to the theoretical concern of bacterial seeding during the procedure many practitioners choose not to sweep the membranes in Group B Streptococcus (GBS) colonized patients. We conducted ‘the STRIP-G study’ in order to determine whether maternal and neonatal outcomes are affected by GBS carrier status in women undergoing membrane stripping.

Study design

We conducted a prospective study in a tertiary referral center, comparing maternal and neonatal outcomes following membrane stripping among GBS-positive, GBS-negative, and GBS-unknown patients. We compared the incidence of composite adverse neonatal outcomes (primary outcome) among the three study groups, while secondary outcome measure was composite adverse maternal outcomes.

Results

A total of 542 women were included in the study, of which 135 were GBS-positive, 361 GBS-negative, and 46 GBS-unknown status. Demographic, obstetric, and intra-partum characteristics were similar for all groups. Adverse neonatal outcomes were observed in 8 (5.9%), 31 (8.6%), and 2 (4.3%) in the GBS-positive, GBS-negative, and unknown groups, respectively (P = 0.530), (Odds Ratio between GBS-Positive vs. GBS-Negative groups 0.67 (95%, CI = 0.30–1.50)); while composite adverse maternal outcomes occurred in 9 (6.66%), 31 (8.59%), and 5 (10.87%) in the GBS-positive, GBS-negative, and unknown groups, respectively (P = 0.617).

Conclusions

Antepartum membrane stripping in GBS carriers appears to be a safe obstetrical procedure that does not adversely affect maternal or neonatal outcomes.