Are propensity scores really superior to standard multivariable analysis?

Clinicians often face difficult decisions despite the lack of evidence from randomized trials. Thus, clinical evidence is often shaped by non-randomized studies exploiting multivariable approaches to limit the extent of confounding. Since their introduction, propensity scores have been used more and more frequently to estimate relevant clinical effects adjusting for established confounders, especially in small datasets. However, debate persists on their real usefulness in comparison to standard multivariable approaches such as logistic regression and Cox proportional hazard analysis. This holds even truer in light of key quantitative developments such as bootstrap and Bayesian methods. This qualitative review aims to provide a concise and practical guide to choose between propensity scores and standard multivariable analysis, emphasizing strengths and weaknesses of both approaches.     

Next-generation drug-eluting stents in coronary artery disease: focus on everolimus-eluting stent (Xience V)

Percutaneous coronary revascularization has been a mainstay in the management of coronary artery disease since its introduction in the late 1970s. Bare-metal stents and, more recently, first-generation drug-eluting stents (DES), such as sirolimus-eluting (Cypher) and paclitaxel-eluting stents (Taxus), have further improved results of percutaneous coronary intervention (PCI) by improving early results and reducing the risk of restenosis. There is currently debate on the safety of these first-generation DES, given the potential for late stent thrombosis, especially after discontinuation of dual antiplatelet therapy. There are well known caveats on the performance of their respective metallic stent platforms, delivery, and dilation systems, and polymer coatings. Second-generation DES, such as zotarolimus-eluting (Endeavor) and everolimus-eluting stents (Xience V), have recently become available in the USA and/or Europe. The Xience V stent holds the promise of superior anti-restenotic efficacy as well as long-term safety. In addition, this stent is based on the Multi-link platform and delivery system. Recently available data already suggest the superiority of the Xience V stent in comparison to the Taxus stent in terms of prevention of restenosis, without significant untoward events. Nonetheless, the number of patients studied and the follow-up duration are still too limited to enable definitive conclusions. Only indirect meta-analyses can be used to date to compare the Xience V with the Cypher. This systematic review tries to provide a concise and critical appraisal of the data in support of the Xience V everolimus-eluting stent.     

The inability of Streptococcus mutans and Lactobacillus acidophilus to form a biofilm in vitro on dentine pretreated with ozone

Background: The use of ozone therapy in the treatment of dental caries is equivocal. The aim of this study was to use an in vitro model to determine the effects of prior ozone application to dentine on biofilm formation and to measure any associated reduction in bacteria viability. Methods: Twenty dentine discs were bonded to the bases of 5 mL polycarbonate screw top vials. Ten dentine discs were infused with ozone for 40 seconds, 10 samples remained untreated as a control. The vials were filled with nutrient medium, sterilized and placed into the outflow from a continuous chemostat culture of Streptococcus mutans and Lactobacillus acidophilus for four weeks. At the conclusion of the experiment bacterial growth was monitored by taking optical density readings of the growth medium in each vial and the outer surface of the dentine specimens were examined by scanning electron microscopy as shown by SEM analysis. Results: Ozone infusion prevented biofilm formation on all the treated samples while there was substantial biofilm present on the control specimens. While the average optical density of the control specimens was almost twice that of the ozone infused dentine (0.710 for the control with a SD of 0.288 and 0.446 for the ozonated samples with a SD of 0.371), the results were not significant (p > 0.05). Conclusions: This preliminary study has shown that the infusion of ozone into non‐carious dentine prevented biofilm formation in vitro from S. mutans and L. acidophilus over a four‐week period. The possibility exists that ozone treatment may alter the surface wettability of dentine through reaction with organic constituents.     

Growth hormone therapy in pre-pubertal children with Noonan syndrome: first year growth response and comparison with Turner syndrome

We studied the growth-promoting effect of treatment with recombinant human growth hormone in 23 prepubertal children with Noonan syndrome, aged between 5. 4 and 14. 3 y, and all with a height < 1. 4 SD for Tanner standards. The growth response and skeletal maturation after 1 y of recombinant human growth hormone treatment (0. 15 U/kg/day given by daily injection) in the Noonan syndrome patients was compared with the auxological changes observed in a group of 17 girls with Turner syndrome with a comparable age and height deficit who were treated with recombinant human growth hormone in a similar way. During 1 y of treatment, the mean ± SD height velocity increased by 4. 0 ± 1. 6 cm/y in the Noonan syndrome group and by 3. 6 ± 1. 3 cm/y in the Turner syndrome group. Height SDS for chronological age in the Noonan syndrome group increased by 0. 53 ± 0. 46 ( p < 0. 001). In the Noonan syndrome patients the changes in height velocity were positively related to birthweight ( r = 0. 48, p < 0. 05). The changes in height velocity or height SDS were not related to the age, height deficit or a delay in bone age maturation at start of treatment. In neither the patients with Noonan syndrome nor Turner syndrome was an acceleration of bone maturation found. We conclude that treatment with recombinant human growth hormone in pre-pubertal NS patients induces an increase in height velocity and height SDS comparable to that observed in Turner syndrome girls.