Index blood tests and national early warning scores within 24 hours of emergency admission can predict the risk of in-hospital mortality: a model development and validation study

BACKGROUND

We explored the use of routine blood tests and national early warning scores (NEWS) reported within ±24 hours of admission to predict in-hospital mortality in emergency admissions, using empirical decision Tree models because they are intuitive and may ultimately be used to support clinical decision making.

METHODOLOGY

A retrospective analysis of adult emergency admissions to a large acute hospital during April 2009 to March 2010 in the West Midlands, England, with a full set of index blood tests results (albumin, creatinine, haemoglobin, potassium, sodium, urea, white cell count and an index NEWS undertaken within ±24 hours of admission). We developed a Tree model by randomly splitting the admissions into a training (50%) and validation dataset (50%) and assessed its accuracy using the concordance (c-) statistic. Emergency admissions (about 30%) did not have a full set of index blood tests and/or NEWS and so were not included in our analysis.

RESULTS

There were 23248 emergency admissions with a full set of blood tests and NEWS with an in-hospital mortality of 5.69%. The Tree model identified age, NEWS, albumin, sodium, white cell count and urea as significant (p<0.001) predictors of death, which described 17 homogeneous subgroups of admissions with mortality ranging from 0.2% to 60%. The c-statistic for the training model was 0.864 (95%CI 0.852 to 0.87) and when applied to the testing data set this was 0.853 (95%CI 0.840 to 0.866).

CONCLUSIONS

An easy to interpret validated risk adjustment Tree model using blood test and NEWS taken within ±24 hours of admission provides good discrimination and offers a novel approach to risk adjustment which may potentially support clinical decision making. Given the nature of the clinical data, the results are likely to be generalisable but further research is required to investigate this promising approach.

ViEWS--Towards a national early warning score for detecting adult inpatient deterioration

AIM OF STUDY

To develop a validated, paper-based, aggregate weighted track and trigger system (AWTTS) that could serve as a template for a national early warning score (EWS) for the detection of patient deterioration.

MATERIALS AND METHODS

Using existing knowledge of the relationship between physiological data and adverse clinical outcomes, a thorough review of the literature surrounding EWS and physiology, and a previous detailed analysis of published EWSs, we developed a new paper-based EWS - VitalPAC EWS (ViEWS). We applied ViEWS to a large vital signs database (n=198,755 observation sets) collected from 35,585 consecutive, completed acute medical admissions, and also evaluated the comparative performance of 33 other AWTTSs, for a range of outcomes using the area under the receiver-operating characteristics (AUROC) curve.

RESULTS

The AUROC (95% CI) for ViEWS using in-hospital mortality with 24h of the observation set was 0.888 (0.880-0.895). The AUROCs (95% CI) for the 33 other AWTTSs tested using the same outcome ranged from 0.803 (0.792-0.815) to 0.850 (0.841-0.859). ViEWS performed better than the 33 other AWTTSs for all outcomes tested.

CONCLUSIONS

We have developed a simple AWTTS - ViEWS - designed for paper-based application and demonstrated that its performance for predicting mortality (within a range of timescales) is superior to all other published AWTTSs that we tested. We have also developed a tool to provide a relative measure of the number of "triggers" that would be generated at different values of EWS and permits the comparison of the workload generated by different AWTTSs.

Health technology assessment review: remote monitoring of vital signs--current status and future challenges

Recent developments in communications technologies and associated computing and digital electronics now permit patient data, including routine vital signs, to be surveyed at a distance. Remote monitoring, or telemonitoring, can be regarded as a subdivision of telemedicine - the use of electronic and telecommunications technologies to provide and support health care when distance separates the participants. Depending on environment and purpose, the patient and the carer/system surveying, analysing or interpreting the data could be separated by as little as a few feet or be on different continents. Most telemonitoring systems will incorporate five components: data acquisition using an appropriate sensor; transmission of data from patient to clinician; integration of data with other data describing the state of the patient; synthesis of an appropriate action, or response or escalation in the care of the patient, and associated decision support; and storage of data. Telemonitoring is currently being used in community-based healthcare, at the scene of medical emergencies, by ambulance services and in hospitals. Current challenges in telemonitoring include: the lack of a full range of appropriate sensors, the bulk weight and size of the whole system or its components, battery life, available bandwidth, network coverage, and the costs of data transmission via public networks. Telemonitoring also has the ability to produce a mass of data - but this requires interpretation to be of clinical use and much necessary research work remains to be done.

Radiative heat pumping from the Earth using surface phonon resonant nanoparticles

Nanoparticles that have narrow absorption bands that lie entirely within the atmosphere's transparent window from 7.9 to 13 mum can be used to radiatively cool to temperatures that are well below ambient. Heating from incoming atmospheric radiation in the remainder of the Planck radiation spectrum, where the atmosphere is nearly "black", is reduced if the particles are dopants in infrared transmitting polymers, or in transmitting coatings on low emittance substrates. Crystalline SiC nanoparticles stand out with a surface phonon resonance from 10.5 to 13 mum clear of the atmospheric ozone band. Resonant SiO(2) nanoparticles are complementary, absorbing from 8 to 10 mum, which includes atmospheric ozone emissions. Their spectral location has made SiC nanoparticles in space dust a feature in ground-based IR astronomy. Optical properties are presented and subambient cooling performance analyzed for doped polyethylene on aluminum. A mixture of SiC and SiO(2) nanoparticles yields high performance cooling at low cost within a practical cooling rig.

Metal-in-metal localized surface plasmon resonance

Anomalous strong resonances in silver and gold nanoporous thin films which conduct are found to arise from isolated metal nano-islands separated from the surrounding percolating metal network by a thin loop of insulator. This observed resonant optical response is modelled. The observed peak position is in agreement with the observed average dimensions of the silver core and insulator shell. As the insulating ring thickness shrinks, the resonance moves to longer wavelengths and strengthens. This structure is the Babinet's principle counterpart of dielectric core-metal shell nanoparticles embedded in dielectric. Like for the latter, tuning of resonant absorption is possible, but here the matrix reflects rather than transmits, and tuning to longer wavelengths is more practical. A new class of metal mirror occurring as a single thin layer is identified using the same resonances in dense metal mirrors. Narrow band deep localized dips in reflectance result.

Measuring clinical performance using routinely collected clinical data

Following the well-publicized problems with paediatric cardiac surgery at the Bristol Royal Infirmary, there is wide public interest in measures of hospital performance. The Kennedy report on the BRI events suggested that such measures should be meaningful to the public, case-mix-adjusted, and based on data collected as part of routine clinical care. We have found that it is possible to predict in-hospital mortality (a measure readily understood by the public) using simple routine data-age, mode of admission, sex, and routine blood test results. The clinical data items can be obtained at a single venesection, are commonly collected in the routine care of patients, are already stored on hospital core IT systems, and so place no extra burden on the clinical staff providing care. Such risk models could provide a metric for use in evidence-based clinical performance management. National application is logistically feasible.