Do risk factors for childhood infections and malnutrition protect against asthma? A study of Brazilian male adolescents

OBJECTIVES: We studied the association between early life conditions and asthma in adolescence. METHODS: We conducted a population-based birth cohort study involving 2250 male 18-year-olds residing in Brazil. RESULTS: Approximately 18% of the adolescents reported having asthma. Several childhood factors were found to be significantly associated with increased asthma risk: being of high socioeconomic status, living in an uncrowded household, and children being breastfed for 9 months or longer. CONCLUSIONS: The present results are consistent with the "hygiene hypothesis," according to which early exposure to infections provides protection against asthma. The policy implications of our findings are unclear given that risk factors for asthma protect against serious childhood diseases in developing countries.     

Do plastic adhesive drapes prevent post caesarean wound infection?

We conducted a prospective randomized controlled double-blind trial at a regional referral centre for the Eastern Cape area, (Livingstone Hospital) to determine whether the use of plastic adhesive drapes intraoperatively would prevent Post Caesarean Section Wound Infection. A total of 620 patients undergoing Caesarean section (CS) were enrolled for randomization in the trial. Fifteen patients were excluded, while 305 received drapes (test group) and 300 did not (control group). Two patients in the control group were subsequently excluded. The primary outcome measure was the presence of Post Caesarean Wound Infection. A secondary outcome measure was the number of days in hospital post operation. The study and control groups were comparable at entry. Results show that 34 patients in the test group (N= 305) developed wound sepsis (11.1%) compared with 30 in the control group (N= 298) (10.1%) (difference not significant; Fisher's exact test 0.6933). Average days spent in hospital postoperatively were similar for both test (infected cases: mean 10.56 SD 3.84; non-infected cases: mean 5.21 SD 1.3) and control groups (infected cases: mean 10.18 SD 3.81; non-infected cases: mean 5.2 SD 0.93) (NS). We concluded that the use of plastic adhesive skin drapes did not avert PCWS or decrease the length of post operative stay in hospital for septic cases.     

Do mixed infections matter? Assessing virulence of mixed-clone infections in experimental human and murine malaria

BackgroundMalaria parasites within an individual infection often consist of multiple strains (clonal populations) of a single species, which have the potential to interact both with one another, and with the host immune system. Several effects of these interactions have been measured in different parasite systems including competition and mutualism; however, direct observation of these effects in human malaria has been limited by sampling complexities and inherent ethical limitations.MethodsUsing multiple complementary epidemiological models, we propose a suite of analyses to more fully utilize data from challenge experiments, and re-examine historical human challenge studies with mixed-strain Plasmodium vivax inocula. We then compare these results with murine model systems using mixed-strain Plasmodium yoelii or Plasmodium chabaudi, to explore the utility of these methods in fully utilizing these data, including the first quantitative estimates of effect sizes for mixed-strain parasitemia. These models also provide a method to assess consistency within these animal model systems.ResultsWe find that amongst a limited set of P. vivax (incubation time) and P. yoelii infections (time-to-mortality), survival times at a study population-level are intermediate between each single-clone infection, and are not dominated by the more virulent clone; in P. vivax relapses, mixed clone infections also show intermediate survival curves. In these infections, the results strongly suggest that highly virulent clones have their virulence attenuated by the presence of less-virulent clones. The analysis of multiple experiments with P. chabaudi suggests greater nuances in the interactions between strains, and that mortality and time-to-event in mixed-strain infections are both indistinguishable from single infections with the more virulent strain.ConclusionsThese divergent dynamics support earlier work that suggested drivers of virulence may differ in fundamental ways between malaria species that are reticulocyte-specific and those that readily infect all red blood cell stages which should be studied in greater detail. The effect sizes (magnitude of biological effects) from these analyses are significant, and suggest the potential for important gains in malaria control by greater incorporation of evolutionary epidemiology theory. Moreover, we suggest that using these epidemiological models may generally allow fuller use of data from experimentally challenging animal model experiments.     

Do parasite infections interfere with immunisation? A review and meta-analysis

Immune responses to vaccination are heterogeneous between individuals; the same vaccine that provides protection in one circumstance may be ineffective in another. One factor that could influence the response to vaccination is concurrent or prior infection with unrelated parasites. Here, we review both the experimental and epidemiological literature on parasite-vaccine interactions, and present a meta-analysis of the published data. In total, our review returned 101 relevant articles, 50 of which met criteria for meta-analysis. Parasite factors potentially affecting vaccination include the type of parasite involved, the stage of infection, and the timing of infection relative to vaccination. Vaccine factors affecting likelihood of interference by parasites include vaccine formulation, route of administration, and the type of immune response required to provide protection against the target antigen. Our meta-analysis of these data show three key things: (1) parasite infections at the time of vaccination result in worse immunisation outcomes, (2) chronic helminth infections are more likely to negatively impact immunisation than acute helminth infections, and (3) thymus-dependent vaccines are more susceptible to parasite interference than thymus-independent vaccines. Our findings highlight the importance of considering and mitigating parasite infections: by taking parasites into account, it should be possible to more effectively immunise individuals and populations.     

Do written action plans improve patient outcomes in asthma? An evidence-based analysis

OBJECTIVE: Current guidelines recommend use of written action plans and peak flow monitoring as key components of asthma care. Our study assesses whether written action plans, with or without peak flow monitoring, have an independent effect on outcomes when used as a component of asthma self-management. STUDY DESIGN: This was a systematic review of published studies. Two independent reviewers followed a prospective protocol for study selection and data abstraction. Outcome data were synthesized qualitatively; they were not appropriate for quantitative meta-analysis. Our comprehensive literature search used MEDLINE, EMBASE, the Cochrane Library, and a hand search of recent bibliographies. The search was limited to full-length, peer-reviewed articles with abstracts in English. The studies were randomized controlled trials that compared the outcomes of an asthma self-management intervention with and without the use a written action plan. The primary outcomes of interest are utilization measures, such as hospitalizations and ER visits. Other outcomes of interest include measures of symptom control and lung function. POPULATION: There were 1501 evaluable patients with asthma; 1410 adults and 91 children. OUTCOMES MEASURED: We measured the frequency of waiting and examination room companions, the reasons for accompaniment, the influence on the encounter, and the overall helpfulness of the companion as assessed by patients and companions. We also determined the physicianamprsquos assessment of the companionamprsquos influence, helpfulness, and behavior during the encounter. RESULTS: Nine randomized controlled trials enrolling a total of 1501 patients met selection criteria. The majority of comparisons in these studies do not demonstrate improved outcomes associated with a written action plan. There are notable methodologic limitations: studies reporting negative findings lack sufficient power, and studies reporting positive findings demonstrate systematic bias. CONCLUSIONS: Although written action plans are widely used, there is insufficient evidence to determine whether their use, with or without peak flow monitoring, improves outcomes.