Statistical inference for decision curve analysis,with applications to cataract diagnosis

Statistical learning methods are widely used in medical literature for the purpose of diagnosis or prediction. Conventional accuracy assessment via sensitivity, specificity, and ROC curves does not fully account for clinical utility of a specific model. Decision curve analysis (DCA) becomes a novel complement as it incorporates a clinical judgment of the relative value of benefits (treating a true positive case) and harms (treating a false positive case) associated with prediction models. The preference of a patient or a policy-maker is formulated statistically as the underlying threshold probability, above which the patient would choose to be treated. Net benefit is then calculated for possible threshold probability, which places benefits and harms on the same scale. We consider the inference problems for DCA in this paper. Interval estimation procedure and inference methodology are provided after we derive the relevant asymptotic properties. Our formulation can accommodate the classification problems with multiple categories. We carry out numerical studies to assess the performance of the proposed methods. An eye disease dataset is analyzed to illustrate our proposals.     

An Easily Assembled,Low-Cost Model for Lateral Canthotomy Education

BackgroundLateral canthotomy is a vision-saving procedure. However, the low incidence of orbital compartment syndrome and the expense of simulators to practice this procedure can lead to low confidence and delays in the performance of the procedure by emergency physicians.DiscussionWe used a simple, inexpensive, easily assembled eye model for lateral canthotomy education at a residency program and a national conference obtaining feedback from simulation participants. Residents rated procedure laboratories that included the lateral canthotomy model as 4.9 to 5 (on a 5-point Likert scale, with 5 being the best score). National conference participants rated the model a 9 as a useful training model for practitioners on a 10-point Likert scale.ConclusionThis simple task trainer is practical, inexpensive, quickly assembled, and useful as a tool for practicing emergency medicine providers.     

Surface roughness of orthodontic band cements with different compositions

Objectives

The present study evaluated comparatively the surface roughness of four orthodontic band cements after storage in various solutions.

Material and Methods

eight standardized cylinders were made from 4 materials: zinc phosphate cement (ZP), compomer (C), resin-modified glass ionomer cement (RMGIC) and resin cement (RC). Specimens were stored for 24 h in deionized water and immersed in saline (pH 7.0) or 0.1 M lactic acid solution (pH 4.0) for 15 days. Surface roughness readings were taken with a profilometer (Surfcorder SE1200) before and after the storage period. Data were analyzed by two-way ANOVA and Tukey''s test (comparison among cements and storage solutions) or paired t-test (comparison before and after the storage period) at 5% significance level.

Results

The values for average surface roughness were statistically different (p<0.001) among cements at both baseline and after storage. The roughness values of cements in a decreasing order were ZP>RMGIC>C>R (p<0.001). After 15 days, immersion in lactic acid solution resulted in the highest surface roughness for all cements (p<0.05), except for the RC group (p>0.05). Compared to the current threshold (0.2 µm) related to biofilm accumulation, both RC and C remained below the threshold, even after acidic challenge by immersion in lactic acid solution.

Conclusions

Storage time and immersion in lactic acid solution increased the surface roughness of the majority of the tested cements. RC presented the smoothest surface and it was not influenced by storage conditions.     

Anal HPV 16 and 18 viral load: A comparison between HIV‐negative and ‐positive MSM and association with persistence

Does anal HPV viral load explain the difference in anal HPV persistence between HIV‐negative and ‐positive men who have sex with men (MSM)? MSM ≥18 years were recruited in Amsterdam, the Netherlands, in 2010‐2011. Anal self‐swabs were collected every 6 months and genotyped (SPF₁₀‐PCR‐DEIA‐LIPA₂₅‐system). HPV16 and HPV18 load was determined with a type specific quantitative (q)PCR, and compared between HIV‐negative and ‐positive men using ranksum test. Persistence was defined as ≥3 positive samples for the same HPV‐type. Determinants of persistent HPV16/18 infection and its association with HPV16/18 load were assessed with logistic regression. Of 777 recruited MSM, 54 and 22 HIV negative men were HPV16 and HPV18 positive at baseline, and 64 and 39 HIV‐positive MSM. The geometric mean titer (GMT) of HPV16 was 19.6 (95%CI 10.1‐38.0) and of HPV18 8.6 (95%CI 2.7‐27.5) DNA copies/human cell. HPV16 and HPV18 load did not differ significantly between HIV‐negative and ‐positive MSM (P = 0.7; P = 0.8, respectively). In multivariable analyses HPV16 load was an independent determinant of HPV16 persistence (OR 1.8, 95%CI 1.3‐2.4). No difference in anal HPV viral load was found between HIV‐positive and HIV‐negative MSM. HPV 16/18 viral load is an independent determinant of type‐specific persistence.     

Penicillin-netilmicin synergism against Streptococcus faecalis.

The combination of penicillin plus netilmicin was synergistic in vitro against 28 strains of Streptococcus faecalis and compared favorably with penicillin in combination with gentamicin. Similarly, penicillin plus netilmicin was as effective as penicillin plus gentamicin in the therapy of 67 rabbits with enterococcal endocarditis produced with a streptomycin-susceptible (S) or a streptomycin-resistant (R) strain of S. faecalis. After 5 days of infection, control rabbits had bacterial titers of 10(10) colony-forming units (CFU)/g of vegetation. Those treated with penicillin plus netilmicin had mean titers of 10(5.2) and 10(5.1) CFU/g for S and R strains, respectively, and those treated with penicillin plus gentamicin had mean valve titers of 10(5.8) CFU/g for both strains. After 10 days of therapy, mean valve titers with penicillin plus netilmicin were 10(3.8) and 10(4.7) CFU/g, and with penicillin plus gentamicin they were 10(4.5) and 10(5.4) CFU/g for S and R strains, respectively. Thus, if netilmicin proves to be less toxic than other aminoglycoside antibiotics, it may have potential usefulness in the therapy of enterococcal endocarditis.     

Eumycetoma and actinomycetoma – an update on causative agents,epidemiology, pathogenesis,diagnostics and therapy

Mycetoma is a chronic putrid infection of the cutaneous and subcutaneous tissue concerning predominantly the feet, and more rarely other body parts. Mycetoma can be caused by both fungi (eumycetoma) and bacteria (actinomycetoma). Mode of infection is an inoculation of the causative microorganism via small injuries of the skin. The clinical correlate of both forms of mycetoma is tumescence with abscesses, painless nodules, sinuses and discharge. The latter is commonly serous‐purulent and contains grains (filamentous granules) which can be expressed for diagnostic purposes. Distinctive for both eumycetoma and actinomycetoma, are the formation of grains. Grains represent microcolonies of the microorganism in vivo in the vital tissue. The most successful treatment option for eumycetomas offers itraconazole in a dosage of 200 mg twice daily. This triazole antifungal is considered as ‘gold standard’ for eumycetomas. Alternatively, the cheaper ketoconazole was widely used, however, it was currently stopped by the FDA. Actinomycetomas should be treated by the combination of trimethoprim‐sulphamethoxazole (co‐trimoxazole 80/400 to 160/800 mg per day) and amikacin 15 mg/kg body weight per day. Mycetomas are neglected infections of the poor. They are more than a medical challenge. In rural areas of Africa, Asia and South America mycetomas lead to socio‐economic consequences involving the affected patients, their families and the society in general.     

Is it possible to stabilize the trunk using rhythmic stabilization in the upper limb? A cross-sectional study of asymptomatic individuals

Objective: The study aim was to evaluate the immediate effect of rhythmic stabilization on local and distant muscles involved in a functional reach. Method: Prospective, observational cross-sectional study. Eight right-handed and non-impaired individuals (4 females and 4 males) aged 18–24 years (21.5 ± 1.58 years) were evaluated. Bilateral electromyographic recording of the biceps brachii, triceps brachii, multifidus lumbar, and rectus abdominis muscles was performed during three different tasks. Task 1 involved functional reach, while Task 2 involved rhythmic stabilization followed by a functional reach. Task 3 was similar to Task 2, but with 3 repetitions before a functional reach. Results: The results showed no difference between the tasks or sides. However, an interaction was observed between each side and muscles, with greater activation of the right multifidus lumbar muscle. Conclusion: Rhythmic stabilization during the task of reaching promotes an increase of multifidus activity ipsilateral to its application. Thus, this particular technique of proprioceptive neuromuscular facilitation can be useful for improving stability of the trunk and can be used in clinical practice for this purpose. Level of Evidence: 5.