Eric W. Wang

A PRACTICAL GUIDE TO UNDERSTANDING KAPLAN-MEIER CURVES

In 1958, Edward L. Kaplan and Paul Meier collaborated to publish a seminal paper on how to deal with incomplete observations. Subsequently, the Kaplan-Meier curves and estimates of survival data have become a familiar way of dealing with differing survival times (times-to-event), especially when not all the subjects continue in the study. “Survival” times need not relate to actual survival with death being the event; the “event” may be any event of interest. Kaplan-Meier analyses are also used in nonmedical disciplines. The purpose of this article is to explain how Kaplan-Meier curves are generated and analyzed. Throughout this article, we will discuss Kaplan-Meier estimates in the context of “survival” before the event of interest. Two small groups of hypothetical data are used as examples in order for the reader to clearly see how the process works. These examples also illustrate the crucially important point that comparative analysis depends upon the whole curve and not upon isolated points.

Pseudomonas aeruginosa Lipopolysaccharide Induces Osteoclastogenesis Through a Toll-Like Receptor 4 Mediated Pathway in Vitro and in Vivo†

Objectives: Bacterial infections near bone result in localized inflammatory osteolysis, a significant complication of chronic ear infections. While many bacterial products may be involved, lipopolysaccharide (LPS) has been implicated as a major mediator of inflammation and osteolysis. However, the mechanisms by which LPS promotes bone resorption have not been clearly established. There is no consensus on whether LPS acts directly or indirectly on osteoclast precursors (bone marrow monocytes [BMM]) to induce bone resorption. In light of the role of Pseudomonas aeruginosa, in chronic ear infections, we investigated the effects of P. aeruginosa LPS on osteoclastogenesis in vivo and in vitro.

A practical guide to understanding systematic reviews and meta-analyses

A systematic review is a transparent and unbiased review of available information. The published systematic review must report the details of the conduct of the review as one might report the details of a primary research project. A meta-analysis is a powerful and rigorous statistical approach to synthesize data from multiple studies, preferably obtained from a systematic review, in order to enlarge the sample size from smaller studies to test the original hypothesis and/or to generate new ones. The objective of this article is to serve as an easy to read practical guide to understand systematic reviews and meta-analyses for those reading them and for those who might plan to prepare them.

Leech-Transmitted Ciprofloxacin-Resistant Aeromonas hydrophila

The use of medicinal leeches ( Hirudo medicinalis ) is effective in establishing venous outflow in congested flaps and replants.Leech therapy also has associated risks, including significant blood loss requiring transfusions and infections from Aeromonas , a gram-negative bacilli.Leeches maintain a symbiotic relationship with Aeromonas species, which are resident to their gut in order to digest blood. Aeromonas hydrophila infections can result in extensive soft-tissue infections and myonecrosis.To prevent this devastating nosocomial infection, ciprofloxacin and/or trimethoprim-sulfamethoxazole (TMP-SMX) are the most commonly used prophylactic antibiotics when patients undergo leech therapy.

Practical guide to understanding the value of case reports

Case reports have been vital to the advancement of medicine, providing a mechanism for scholarly education and for sharing new discovery and rare observations. However, journals are increasingly reluctant to publish this type of manuscript. Additionally, case reports and limited case series are infrequently cited, potentially interfering with the impact factor of a journal. The increasing emphasis on evidence-based medicine may have artificially decreased the value of case reports. This article describes the value of case reports to medicine, citing 3 examples that have significantly improved the practice of medicine. We also provide criteria for effective reporting, which include the elements of both surprise and closure. In summary, we offer support for the contention that case reports are fundamental to the scholarly practice of medicine and enhance the intent of a quality medical journal.

Gentian violet and ferric ammonium citrate disrupt Pseudomonas aeruginosa biofilms.

Objective/Hypothesis: Bacterial biofilms are resistant to antibiotics and may contribute to persistent infections including chronic otitis media and cholesteatoma. Discovery of substances to disrupt biofilms is necessary to treat these chronic infections. Gentian violet (GV) and ferric ammonium citrate (FAC) were tested against Pseudomonas aeruginosa biofilms to determine if either substance can reduce biofilm volume.

P. aeruginosa Infection Increases Morbidity in Experimental Cholesteatomas

Clinicians have long noted that infected cholesteatomas are more aggressive than uninfected ones without data to support these observations. The purpose of this study is to determine the etiological role of biofilm forming P. aeruginosa (PA) and the virulence factor, type IV pili (TFP), in the pathogenesis of experimental cholesteatomas.

A practical guide for understanding confidence intervals and P values

The 95 percent confidence interval about the mean demarcates the range of values in which the mean would fall if many samples from the universal parent population were taken. In other words, if the same observation, experiment, or trial were done over and over with a different sample of subjects, but with the same characteristics as the original sample, 95 percent of the means from those repeated measures would fall within this range. This gives a measure of how confident we are in the original mean. It tells us not only whether the results are statistically significant because the CI falls totally on one side or the other of the no difference marker (0 if continuous variables; 1 if proportions), but also the actual values so that we might determine if the data seem clinically important. In contrast, the P value tells us only whether the results are statistically significant, without translating that information into values relative to the variable that was measured. Consequently, the CI is a better choice to describe the results of observations, experiments, or trials.

Practical guide to efficient analysis and diagramming articles.

OBJECTIVE: In a busy practice, time is a commodity in rare supply, and keeping abreast of the relevant medical literature is a daunting task. Even after reading an article carefully, important information may be lost because of undue attention to the methodological minutia. METHOD: Fundamental to reducing a complex article into a well-organized and consistent format is the technique of quantitatively diagramming the principal components in the design and findings of the study. This approach allows a coherent brief summary statement of the article, and a platform for a focused scientific discussion and analysis of the clinical applicability of the findings. CONCLUSIONS: The technique of diagramming an article is a tool that the senior author has used for years and has found it valuable in capturing the scientific fundamentals of a manuscript. Once prepared, the diagram has proven to be useful in clarifying presentations during journal club, preparing the background and significance sections of grant applications, reviewing articles as a journal editor and as a journal reviewer, and easily retrieving documents to support evidence-based practice efforts.