Tests for Independence in Two-Way Contingency Tables with Small Samples

When testing the null hypothesis of independence in a two-way contingency table, the likelihood ratio test statistic is approximately distributed as Chi-squared d for large sample sizes (N) but may not be for small samples. This paper presents expressions which match the mean of the statistic to Chi-squared d as far as N−1 and N−2, derives a method of estimating the expressions from observed data and evaluates them using Monte Carlo simulations. It is concluded that using appropriate dividing factors, rejection rates after matching are more accurate than for either the unadjusted likelihood ratio statistic or the Pearson approximation which is the main alternative statistic. Minimum cell frequencies necessary for high test accuracy are smaller than those commonly given in textbooks

Gated metabolic myocardial imaging, a surrogate for dual perfusion-metabolism imaging by positron emission tomography

Acknowledgments The authors are grateful for the help from Dr H Ali and Dr A Dawson. Funding: This study was performed using a research grant from the Aberdeen Royal Hospitals Trust's Endowment Fund, with further support from the Department of Medical Physics at the University of Aberdeen, for which the authors express their gratitude.Peer reviewedPublisher PD

GPs' perceptions of advance care planning with frail and older people: a qualitative study.

BACKGROUND: Frail and older people are estimated to account for 40% of deaths. Despite conversations about end-of-life care being an important component of the national End of Life Care Strategy, there is a marked disparity between the majority who would like to discuss advance care plans, and the minority who currently have this opportunity. AIM: To investigate the attitudes of GPs to advance care planning (ACP) discussions with frail and older individuals. DESIGN AND SETTING: Focus group study with GPs in Cambridgeshire between September 2015 and January 2016. METHOD: Five focus groups with 21 GPs were purposively sampled to maximise diversity. Framework analysis was used to analyse transcripts and develop themes. RESULTS: Although some GPs were concerned it might cause distress, the majority felt that raising ACP was important, especially as preparation for future emergencies. Knowing the individuals, introducing the idea as part of ongoing discussions, and public awareness campaigns were all facilitators identified. Several considered that service limitations made it difficult to fulfil patients' wishes and risked raising unrealistic patient expectations. Other barriers identified included uncertainty over prognosis and difficulties ensuring that individuals' wishes were respected. CONCLUSION: Most GPs viewed ACP as important. However, their enthusiasm was tempered by experience. This study highlights the difficulties for GPs of encouraging dialogue and respecting individuals' wishes within the constraints of the existing health and social care system. National publicity campaigns and encouraging patients to prioritise healthcare outcomes could help GPs raise care preferences without causing a detrimental impact on patients or raising unrealistic expectations. Once patients agree their care preferences, they need to be documented, accessible, and reviewed by all relevant health and social care providers to ensure that their wishes are respected, and plans amended as their circumstances change

A rapid, chromatography-free route to substituted acridine–isoalloxazine conjugates under microwave irradiation

Microwave irradiation was applied to a sequence of condensation reactions from readily available 9-chloroacridines to provide a range of novel acridine–isoalloxazine conjugates. The combination of these two moieties, both of biological interest, was achieved by a chromatography free route