The care and feeding of evidence based medicine.

Wide interest in evidence based medicine (EBM) and its value in patient care, insurance payment decisions, and public health planning has triggered intense medical journal and media coverage that merits review, explanation, and comment. Published EBM data vary in quality for reasons that have been the subject of many perceptive literature reviews. Study design can be faulted, and conflicts of interest, personal and economic, can potentially bias study results and their publication. Practical guides for data evaluation are presented here, with discussion of technical and sociological issues that affect information quality and its clinical application. Clinical practice often appears to resist good evidence in making clinical choices. Personal views of some practicing physicians about EBM are presented that underlie the occasional difficulties in applying valid research information in patient care. Improvements in study design and publication standards may enhance the clinical application of evidence-based information. EBM guided practice holds promise to improve outcomes and expense, to standardize and streamline process in ways that make for much safer patient care.

Koch's postulates, carnivorous cows, and tuberculosis today.

With Koch's announcement in 1882 of his work with the tubercle bacillus, his famous postulates launched the rational world of infectious disease and an abrupt social change--strict patient isolation. The postulates, so successful at their inception, soon began to show some problems, particularly with cholera, which clearly violated some of Koch's requirements. Subsequent studies of other diseases and the discovery of entirely new ones have so altered and expanded the original postulates that they now are little but a precious touch of history. The present additions and replacements of the original concepts are skillful changes that several authors have devised to introduce new order into understanding complex viral and prion diseases. In 1988, this knowledge, with the totally rational response of the British population and its cattle industry, was critical in promptly blocking the threatened epidemic of human prion disease. In contrast, the recent upsurge of tuberculosis (TB) in the worldwide AIDS epidemic in developing countries, and the sudden increase in metabolic syndrome in wealthy ones, suggests the need for focused sociobiologic research seeking ways to affect the damaging lifestyle behavior of many less educated populations in both settings. The world awaits an equivalent of Koch's Postulates in sociobiology to explain and possibly avert large self-destructive behaviors.

Human injury from atomic particles and photon exposure: fears, myths, risks, and mortality.

Energy absorbtion from particles and photons moving at relativistic speeds has been a fundamental part of life on earth and wherever else life might exist. Heat and visible light have deeply influenced the course of human evolution, affecting habitat and nutrition. The photons of ionizing radiation that over time can possibly affect evolution, contribute to the more immediate problem of morbidity and mortality of cancer This review addresses our radiative energy absorbtion, from both natural and manmade sources, and its relationship with disease and death. Educational Public Health efforts to offset the dangers of solar ultraviolet overexposure are presented, together with data on the significant mortality of metastatic melanoma.

Reproducibility of ultrasound scan in the assessment of volume flow in the veins of the lower extremities.

PURPOSE: The purpose of this study was the identification of the optimal settings of ultrasound scan flow measurement in the veins and the determination of whether the standardization of these settings can provide acceptable reproducibility of the venous flow measurements in individual segments of the lower extremity veins. METHODS: The venous cross-sectional area, the time average mean velocity, and the venous volume flow of 25 healthy volunteers were examined with duplex ultrasound scanning. Reproducibility was examined with different measurement settings. Doppler scan sample volume size, ultrasound scan beam incident angle, and time interval of measurement were varied across a spectrum for arrival at the setting for highest reproducibility of the flow volume measurements. Test-retest reproducibility of venous flow volume measurements then was investigated with optimized settings. RESULTS: The highest repeatability of volume flow measurements was achieved when the full lumen of the vein was insonated (coefficient of repeatability [CR] = 1.88 cm/s), the ultrasound scan beam incident angle was equal to 60 degrees (CR = 1.56 cm/s), and the measurement time was more than 40 seconds (CR = 1.64 cm/s). The mean values of volume flow were 360 mL/min in the common femoral vein, 147 mL/min in the superficial femoral vein, 86 mL/min in the profunda femoral vein, and 38 mL/min in the greater saphenous vein. Test-retest repeatability coefficients were 96.9 mL/min for the common femoral vein, 70.2 mL/min for the superficial femoral vein, 40.8 mL/min for the profunda femoral vein, and 16.8 mL/min for the greater saphenous vein. CONCLUSION: The reproducibility of ultrasound scan measurements of volume flow in veins is optimized with the use of sampling volumes that cover the entire venous lumen, with an incident angle of 60 degrees and measuring for 40-second intervals or longer. With these defined variables, volumetric measurements are sufficiently repeatable. the values of flow volume measured with duplex ultrasound scanning were comparable to those with thermodilution techniques that were reported previously.