Examining the effect of evaluation sample size on the sensitivity and specificity of COVID-19 diagnostic tests in practice: a simulation study

Background: In response to the global COVID-19 pandemic, many in vitro diagnostic (IVD) tests for SARS-CoV-2 have been developed. Given the urgent clinical demand, researchers must balance the desire for precise estimates of sensitivity and specificity against the need for rapid implementation. To complement estimates of precision used for sample size calculations, we aimed to estimate the probability that an IVD will fail to perform to expected standards after implementation, following clinical studies with varying sample sizes. Methods: We assumed that clinical validation study estimates met the ‘desirable’ performance (sensitivity 97%, specificity 99%) in the target product profile (TPP) published by the Medicines and Healthcare products Regulatory Agency (MHRA). To estimate the real-world impact of imprecision imposed by sample size we used Bayesian posterior calculations along with Monte Carlo simulations with 10,000 independent iterations of 5,000 participants. We varied the prevalence between 1 and 15% and the sample size between 30 and 2,000. For each sample size, we estimated the probability that diagnostic accuracy would fail to meet the TPP criteria after implementation. Results: For a validation study that demonstrates ‘desirable’ sensitivity within a sample of 30 participants who test positive for COVID-19 using the reference standard, the probability that real-world performance will fail to meet the ‘desirable’ criteria is 10.7–13.5%, depending on prevalence. Theoretically, demonstrating the 'desirable' performance in 90 positive participants would reduce that probability to below 5%. A marked reduction in the probability of failure to hit ‘desirable’ specificity occurred between samples of 100 (19.1–21.5%) and 160 (4.3–4.8%) negative participants. There was little further improvement above sample sizes of 160 negative participants. Conclusion: Based on imprecision alone, small evaluation studies can lead to the acceptance of diagnostic tests which are likely to fail to meet performance targets when deployed. There is diminished return on uncertainty surrounding an accuracy estimate above a total sample size of 250 (90 positive and 160 negative)

Assessment of operator variation in flow cytometry measurements using gauge repeatability & reproducibility techniques

Assessment of operator variation in flow cytometry measurements using gauge repeatability & reproducibility technique

Detection of cortisol in serum using quantitative resonance Raman spectroscopy

Measurement of cortisol in serum is used commonly as an indicator of stress and disease. Conventional analytical techniques have limited utility given that they remain largely laboratory based, they do not directly measure the deemed biologically active free cortisol, and there is no robust correlation between the free cortisol measurements within serum and saliva. It would therefore be desirable to measure both the free and total cortisol readily within the same matrix in a portable device in the field or at the bedside. This paper demonstrates the utility of a portable Raman approach to measure both the biological active free cortisol as well as total cortisol in human serum, compared to a laboratory-based chemiluminescence analysis technique. This alternative portable Raman method produced results that were consistent with results obtained from previous methods, which has the potential for further miniaturisation for point of test applications

Investigation of bovine serum albumin denaturation using ultrasonic spectroscopy

The ability of ultrasound spectroscopy to characterise protein denaturation at relatively high concentrations and under conditions found in foods, is examined. Measurement of longitudinal sound velocity against concentration and frequency (20-160 MHz) for the bovine serum albumin monomer at pH 7.0 gave a frequency independent value for molecular compressibility of at 25 °C, corresponding to a sound velocity for the BSA molecule of 1920 ms-1. At 160 MHz, the longitudinal sound attenuation in BSA molecules is ~5200 Npm-1, a factor of 10 higher than in water. The excess attenuation of the solution over water was nearly 90 Npm-1 at the highest measured volume fraction of 0.03 (or 3% v/v). Concentration-dependent ultrasound velocity (20 - 160 MHz) and attenuation (2 - 120 MHz) spectra were obtained over time for heated bovine serum albumin (BSA) solutions up to 40 mg/mL at neutral pH and at 25 °C. An acoustic scattering model was used which considered the solute molecules as scatterers of ultrasound, to determine the molecules' sound velocity, compressibility, and attenuation properties. Mild heat treatment caused the molecule to organise into dimers and trimers, without change in sound velocity; implying that there is little or no change in secondary structure. Changes in attenuation spectra correlated with estimated molecular weight as determined through DLS and SEC measurements. During oligomerisation, the BSA molecules continue to behave acoustically as monomers. Under severe heat treatment, BSA rapidly suffered irreversible denaturation and gelation occurred which affected both ultrasound attenuation spectra and the velocity of sound, consistent with significant molecular conformation changes and/or molecule-molecule interactions

Operator measurement uncertainty contributions within post-analytical flow cytometry data [poster]

Operator measurement uncertainty contributions within post-analytical flow cytometry data [poster

Comparability: manufacturing, characterization and controls, report of a UK Regenerative Medicine Platform Pluripotent Stem Cell Platform Workshop, Trinity Hall, Cambridge, 14–15 September 2015

This paper summarizes the proceedings of a workshop held at Trinity Hall, Cambridge to discuss comparability and includes additional information and references to related information added subsequently to the workshop. Comparability is the need to demonstrate equivalence of product after a process change; a recent publication states that this ‘may be difficult for cell-based medicinal products’. Therefore a well-managed change process is required which needs access to good science and regulatory advice and developers are encouraged to seek help early. The workshop shared current thinking and best practice and allowed the definition of key research questions. The intent of this report is to summarize the key issues and the consensus reached on each of these by the expert delegates

Investigation of bovine serum albumin denaturation using ultrasonic spectroscopy

This is the author’s version of a work that was accepted for publication in the journal Food Hydrocolloids. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.foodhyd.2010.11.011The ability of ultrasound spectroscopy to characterise protein denaturation at relatively high concentrations and under conditions found in foods, is examined. Measurement of longitudinal sound velocity against concentration and frequency (20-160 MHz) for the bovine serum albumin monomer at pH 7.0 gave a frequency independent value for molecular compressibility of at 25 °C, corresponding to a sound velocity for the BSA molecule of 1920 ms-1. At 160 MHz, the longitudinal sound attenuation in BSA molecules is ~5200 Npm-1, a factor of 10 higher than in water. The excess attenuation of the solution over water was nearly 90 Npm-1 at the highest measured volume fraction of 0.03 (or 3% v/v). Concentration-dependent ultrasound velocity (20 - 160 MHz) and attenuation (2 - 120 MHz) spectra were obtained over time for heated bovine serum albumin (BSA) solutions up to 40 mg/mL at neutral pH and at 25 °C. An acoustic scattering model was used which considered the solute molecules as scatterers of ultrasound, to determine the molecules' sound velocity, compressibility, and attenuation properties. Mild heat treatment caused the molecule to organise into dimers and trimers, without change in sound velocity; implying that there is little or no change in secondary structure. Changes in attenuation spectra correlated with estimated molecular weight as determined through DLS and SEC measurements. During oligomerisation, the BSA molecules continue to behave acoustically as monomers. Under severe heat treatment, BSA rapidly suffered irreversible denaturation and gelation occurred which affected both ultrasound attenuation spectra and the velocity of sound, consistent with significant molecular conformation changes and/or molecule-molecule interactions

Multicenter Diagnostic Evaluation of OnSite COVID-19 Rapid Test (CTK Biotech) among Symptomatic Individuals in Brazil and the United Kingdom

Evaluating rapid diagnostic tests in diverse populations is essential to improving diagnostic responses as it gives an indication of the accuracy in real-world scenarios. In the case of rapid diagnostic testing within this pandemic, lateral flow tests that meet the minimum requirements for sensitivity and specificity can play a key role in increasing testing capacity, allowing timely clinical management of those infected, and protecting health care systems

Effect of remote ischaemic conditioning on clinical outcomes in patients with acute myocardial infarction (CONDI-2/ERIC-PPCI): a single-blind randomised controlled trial.

BACKGROUND: Remote ischaemic conditioning with transient ischaemia and reperfusion applied to the arm has been shown to reduce myocardial infarct size in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). We investigated whether remote ischaemic conditioning could reduce the incidence of cardiac death and hospitalisation for heart failure at 12 months. METHODS: We did an international investigator-initiated, prospective, single-blind, randomised controlled trial (CONDI-2/ERIC-PPCI) at 33 centres across the UK, Denmark, Spain, and Serbia. Patients (age >18 years) with suspected STEMI and who were eligible for PPCI were randomly allocated (1:1, stratified by centre with a permuted block method) to receive standard treatment (including a sham simulated remote ischaemic conditioning intervention at UK sites only) or remote ischaemic conditioning treatment (intermittent ischaemia and reperfusion applied to the arm through four cycles of 5-min inflation and 5-min deflation of an automated cuff device) before PPCI. Investigators responsible for data collection and outcome assessment were masked to treatment allocation. The primary combined endpoint was cardiac death or hospitalisation for heart failure at 12 months in the intention-to-treat population. This trial is registered with ClinicalTrials.gov (NCT02342522) and is completed. FINDINGS: Between Nov 6, 2013, and March 31, 2018, 5401 patients were randomly allocated to either the control group (n=2701) or the remote ischaemic conditioning group (n=2700). After exclusion of patients upon hospital arrival or loss to follow-up, 2569 patients in the control group and 2546 in the intervention group were included in the intention-to-treat analysis. At 12 months post-PPCI, the Kaplan-Meier-estimated frequencies of cardiac death or hospitalisation for heart failure (the primary endpoint) were 220 (8·6%) patients in the control group and 239 (9·4%) in the remote ischaemic conditioning group (hazard ratio 1·10 [95% CI 0·91-1·32], p=0·32 for intervention versus control). No important unexpected adverse events or side effects of remote ischaemic conditioning were observed. INTERPRETATION: Remote ischaemic conditioning does not improve clinical outcomes (cardiac death or hospitalisation for heart failure) at 12 months in patients with STEMI undergoing PPCI. FUNDING: British Heart Foundation, University College London Hospitals/University College London Biomedical Research Centre, Danish Innovation Foundation, Novo Nordisk Foundation, TrygFonden

Effects of paramagnetic and ferromagnetic particles on magnetic resonance (MR) imaging.

This thesis is not available on this repository until the author agrees to make it public. If you are the author of this thesis and would like to make your work openly available, please contact us: [email protected] Library can supply a digital copy for private research purposes; interested parties should submit the request form here: http://www.lib.cam.ac.uk/collections/departments/digital-content-unit/ordering-imagesPlease note that print copies of theses may be available for consultation in the Cambridge University Library's Manuscript reading room. Admission details are at http://www.lib.cam.ac.uk/collections/departments/manuscripts-university-archive