Updated: Dec 8, 2021
Lateral flow tests
Lateral flow tests (LFT) are increasingly ubiquitous. Less sensitive than the gold-standard PCR swabs, but they provide results in 20-30 minutes rather than a day or more. Together with vaccines, they have been welcomed for their potential to unlock key aspects of our pre-COVID lives that are off-limits for now. However, there are significant concerns over operator error (79% accuracy with trained laboratory scientists vs 58% with track and trace centre staff), false positives and the ability to pick up asymptomatic cases (evidence from prior roll-outs in Liverpool and University of Birmingham). Since the return of all secondary schools in England on 8 March, students have been expected to test themselves at home 2-3 times a week. Is this appropriate and effective? Is lower sensitivity being compounded by problems in collecting the sample or failure to report positive cases because of the consequences? The all-in cost of delivering LFT kits is of the order of £10. Positivity rates from schools according to NHS Test and Trace at the end of February were 0.2% (5k out of 2.2m) Perhaps as many as half of these are likely to be false positives, given the specificity of the kits and prevalence of the virus. This would imply a cost of around £10K for each true positive case, or a running cost across secondary schools of £30 million a week. Every unreported case or poorly carried out swab reduces both the value and the purpose of the whole endeavour.
Optimising vaccine centre operation
The announcement today that over-70s in the UK are to be offered a further vaccination booster in September confirms the reality that vaccination is the new norm, and healthcare delivery needs to be as optimal as possible to conserve resources. National guidance at the start of the vaccination programme was that 2-vaccinator pods should be able to vaccinate 520 people over 12 hours. A joint study by the NHS and University of Bath used an open source R-based discrete event simulation for modelling patient pathways to evaluate optimal throughput through different stages of the vaccination process. Computer modelling was combined with real-life simulation and consideration of threat scenarios. Application of different solutions and monitoring activity at two different sites in South-West England illustrated a variety of learnings and enhancements. Combining clinical assessment and vaccination avoided repetition of information and greetings. Maximising throughput reduced resilience and increased likelihood of excessive and unsafe queues. Bespoke processes and levels of experience at sites can lead to very different activity times with, for example, the clinical assessment/vaccination phase taking 200 seconds at one site (Site A), but 390 seconds at another (Site B). Time spent waiting could be converted to time spent preparing. Capturing data, modelling queuing parameters and implementing sequential improvements could mean that more sites are able to meet and exceed the performance of Site B with a 2-vaccinator pod throughput of 870 people every 12 hours.