Survival bias may explain the appearance of the obesity paradox in hip fracture patients.

Patients with low-energy hip fractures do not follow the obesity paradox as previously reported. In datasets where injury mechanism is not available, the use of age >50 years (as opposed to commonly used >65 years) as a surrogate for a low-energy hip fracture patients may be a more robust inclusion criterion. PURPOSE: In elderly patients with a hip fracture, limited data suggests that obese patients counterintuitively have improved survival compared to normal-weight patients. This "obesity paradox" may be the byproduct of selection bias. We hypothesized that the obesity paradox would not apply to elderly hip fracture patients. METHODS: The National Surgical Quality Improvement Project dataset identified 71,685 hip fracture patients ≥50 years-of-age with complete body mass index (BMI) data that underwent surgery. Patients were stratified into under and over 75-year-old cohorts (n=18,956 and 52,729, respectively). Within each age group, patients were stratified by BMI class and compared with respect to preoperative characteristics and 30-day mortality. Significant univariate characteristics (p<0.1) were included in multivariate analysis to determine the independent effect of obesity class on 30-day mortality (p<0.05). RESULTS: Multivariate analysis of <75-year-old patients with class-III obesity were more likely to die within 30-days than similarly aged normal-weight patients (OR 1.91, CI 1.06-3.42, p=0.030). Multivariate analysis of ≥75-year-old overweight (OR 0.69, CI 0.62-0.77, p<0.001), class-I obese (OR 0.62, CI 0.51-0.74, p<0.001), or class-II obese (OR=0.69, CI 0.50-0.95, p=0.022) patients were less likely to die within 30-days when compared to similarly aged normal-weight patients. CONCLUSIONS: Our data suggest that obesity is a risk factor for mortality in low-energy hip fracture patients, but the appearance of the "obesity paradox" in elderly hip fracture patients results from statistical bias that is only evident upon subgroup analysis.

A hand-held surface plasmon resonance biosensor for the detection of ricin and other biological agents.

There is an ongoing need for field-deployable biosensor devices. We have constructed a fully self-contained, hand-held biosensor, based on the surface plasmon resonance technique. The dimensions of the sensor unit are 15 x 8 cm, the weight is 600 g and it is powered by a 9 V battery. We have characterised the responsiveness of the sensor using calibrated sucrose solutions and were able to measure changes as small as 3.3 x 10(-6) refractive index units. To demonstrate functionality of the sensor, we have prepared surfaces with an antibody fragment specific for the biological toxin ricin. We were able to detect ricin at 200 ng/mL in 10 min, which is approximately 2500 times less than the minimum lethal dose. We were also able to verify positive binding within a second 10 min window. This sensor demonstrates important steps required for the development of fully integrated, hand-held sensor devices and will form the basis of a multi-analyte system, to be developed in the near future. It also represents the first completely hand-held SPR device, not requiring external power or a computer connection to operate.

Clinical assessment of ankylosing spondylitis: a study of observer variation in spinal measurements.

Twenty-two measurements repeated non-sequentially on each of 10 patients by five observers were undertaken to determine their reliability for routine clinical use. Measurements without significant inter-observer variation or with a coefficient of reliability greater than 0.70 were cervical rotation, cervical lateral flexion, tragus to wall distance, fingertip to floor distance on sagittal and lateral flexion, C7 to iliac crest line distraction and modified Schober index. It is concluded that many of the currently used measurements are either statistically unreliable or clinically unhelpful in mild or moderate ankylosing spondylitis. The most clinically useful were cervical rotation using a protractor, cervical lateral flexion using a goniometer, thoracolumbar flexion as the C7 to iliac crest line distraction, thoracolumbar lateral flexion as the fingertip to floor distance and the modified Schober index.