Costs and Consequences of a Novel Emergency Department Sepsis Diagnostic Test: The IntelliSep Index.

Sepsis causes 270,000 deaths and costs $38 billion annually in the United States. Most cases of sepsis present in the emergency department (ED), where rapid diagnosis remains challenging. The IntelliSep Index (ISI) is a novel diagnostic test that analyzes characteristics of WBC structure and provides a reliable early signal for sepsis. This study performs a cost-consequence analysis of the ISI relative to procalcitonin for early sepsis diagnosis in the ED. PERSPECTIVE: U.S. healthcare system. SETTING: Community hospital ED. METHODS: A decision tree analysis was performed comparing ISI with procalcitonin. Model parameters included prevalence of sepsis, sensitivity and specificity of diagnostic tests (both ISI and procalcitonin), costs of hospitalization, and mortality rate stratified by diagnostic test result. Mortality and prevalence of sepsis were estimated from best available literature. Costs were estimated based on an analysis of a large, national discharge dataset, and adjusted to 2018 U.S. dollars. Outcomes included expected costs and survival. RESULTS: Assuming a confirmed sepsis prevalence of 16.9% (adjudicated to Sepsis-3), the ISI strategy had an expected cost per patient of $3,849 and expected survival rate of 95.08%, whereas the procalcitonin strategy had an expected cost of $4,656 per patient and an expected survival of 94.98%. ISI was both less costly and more effective than procalcitonin, primarily because of fewer false-negative results. These results were robust in sensitivity analyses. CONCLUSIONS: ISI was both less costly and more effective in preventing mortality than procalcitonin, primarily because of fewer false-negative results. The ISI may provide health systems with a higher-value diagnostic test in ED sepsis evaluation. Additional work is needed to validate these results in clinical practice.

Whole-body photoreceptor networks are independent of 'lenses' in brittle stars.

Photoreception and vision are fundamental aspects of animal sensory biology and ecology, but important gaps remain in our understanding of these processes in many species. The colour-changing brittle star Ophiocoma wendtii is iconic in vision research, speculatively possessing a unique whole-body visual system that incorporates information from nerve bundles underlying thousands of crystalline 'microlenses'. The hypothesis that these might form a sophisticated compound eye-like system regulated by chromatophores has been extensively reiterated, with investigations into biomimetic optics and similar supposedly 'visual' structures in living and fossil taxa. However, no photoreceptors or visual behaviours have ever been identified. We present the first evidence of photoreceptor networks in three Ophiocoma species, both with and without microlenses and colour-changing behaviour. High-resolution microscopy, immunohistochemistry and synchrotron tomography demonstrate that putative photoreceptors cover the animals' oral, lateral and aboral surfaces, but are absent at the hypothesized focal points of the microlenses. The structural optics of these crystal 'lenses' are an exaptation and do not fulfil any apparent visual role. This contradicts previous studies, yet the photoreceptor network in Ophiocoma appears even more widespread than previously anticipated, both taxonomically and anatomically.