Sample size recalculation based on the prevalence in a randomized test-treatment study

Sample size recalculation based on the overall success rate in a randomized test-treatment trial with restricting randomization to discordant pairs

BACKGROUND

Randomized test-treatment studies are performed to evaluate the clinical effectiveness of diagnostic tests by assessing patient-relevant outcomes. The assumptions for a sample size calculation for such studies are often uncertain.

METHODS

An adaptive design with a blinded sample size recalculation based on the overall success rate in a randomized test-treatment trial with restricting randomization to discordant pairs is proposed and evaluated by a simulation study. The results of the adaptive design are compared to those of the fixed design.

RESULTS

The empirical type I error rate is sufficiently controlled in the adaptive design as well as in the fixed design and the estimates are unbiased. The adaptive design achieves the desired theoretical power, whereas the fixed design tends to be over- or under-powered.

CONCLUSIONS

It may be advisable to consider blinded recalculation of sample size in a randomized test-treatment study with restriction of randomization to discordant pairs in order to improve the conduct of the study. However, there are a number of study-related limitations that affect the implementation of the method which need to be considered.

Point-of-care tests in the emergency medical services: a scoping review

BACKGROUND

This scoping review aimed to summarize existing research on point-of-care tests (POCTs) within emergency medical services (EMS). There is a lack of comprehensive reviews covering the breadth and scope of application of POCTs in EMS despite growing interest and potential benefits in this setting. A review of the research will inform how we target future research efforts to support effective implementation and avoid duplication.

METHODS

We searched three databases to April 2023 using comprehensive terms for POCTs. One author screened titles and abstracts, full-text papers and extracted data with a second author checking the data. A scoping review framework was used to categorise studies according to demographics, study design, medical conditions, biomarkers and test devices.

RESULTS

We found 141 papers that included 158 reports of 9 study designs, 155 reports of 40 combinations of biomarker and condition and 161 reports of 41 test-devices. The majority of research was done in the UK (19%), US (17%), and the Netherlands (16%), mostly in land-based EMS (82%). Most frequently assessed were troponin for acute coronary syndromes (26%), lactate for sepsis (14%) or lactate for trauma/critical illness (13%). The majority of research designs investigated the accuracy of the tests (43%). Few studies were of a design to inform guidelines to change patient pathways and the associated outcomes, including, randomised controlled trials (RCTs) (4%), non-randomised studies able to assess causality (6%), economic analyses (1%) or qualitative work on acceptability (3%). In those few cases where RCTs were done there were long delays between initial test-accuracy research and publication of the first RCT, for example 11 years delay for troponin for acute coronary syndromes.

CONCLUSIONS

We identified a thriving base of research on POCT in the EMS, however most studies established the diagnostic accuracy of the tests with few RCTs, economic analyses or qualitative research on acceptability. The time-lag from diagnostic accuracy to developing an RCT is considerable. Investment in funding and infrastructure is needed to support the research pathway for potential POCTs beyond diagnostic accuracy to designs able to assess clinical effectiveness, acceptability and economic effectiveness.

A unified framework for diagnostic test development and evaluation during outbreaks of emerging infections

Evaluating diagnostic test accuracy during epidemics is difficult due to an urgent need for test availability, changing disease prevalence and pathogen characteristics, and constantly evolving testing aims and applications. Based on lessons learned during the SARS-CoV-2 pandemic, we introduce a framework for rapid diagnostic test development, evaluation, and validation during outbreaks of emerging infections. The framework is based on the feedback loop between test accuracy evaluation, modelling studies for public health decision-making, and impact of public health interventions. We suggest that building on this feedback loop can help future diagnostic test evaluation platforms better address the requirements of both patient care and public health.

A diagnostic phase III/IV seamless design to investigate the diagnostic accuracy and clinical effectiveness using the example of HEDOS and HEDOS II

The development process of medical devices can be streamlined by combining different study phases. Here, for a diagnostic medical device, we present the combination of confirmation of diagnostic accuracy (phase III) and evaluation of clinical effectiveness regarding patient-relevant endpoints (phase IV) using a seamless design. This approach is used in the Thyroid HEmorrhage DetectOr Study (HEDOS & HEDOS II) investigating a post-operative hemorrhage detector named ISAR-M THYRO® in patients after thyroid surgery. Data from the phase III trial are reused as external controls in the control group of the phase IV trial. An unblinded interim analysis is planned between the two study stages which includes a recalculation of the sample size for the phase IV part after completion of the first stage of the seamless design. The study concept presented here is the first seamless design proposed in the field of diagnostic studies. Hence, the aim of this work is to emphasize the statistical methodology as well as feasibility of the proposed design in relation to the planning and implementation of the seamless design. Seamless designs can accelerate the overall trial duration and increase its efficiency in terms of sample size and recruitment. However, careful planning addressing numerous methodological and procedural challenges is necessary for successful implementation as well as agreement with regulatory bodies.