Should we reconsider blocking the thyroid for 123 I-Ioflupane studies in elderly patients: quantifying radiation dose to the unblocked thyroid and implications for clinical practice.

OBJECTIVES: To measure the absorbed dose to the thyroid in patients injected with 123 I-Ioflupane where the thyroid was not blocked with prophylaxis to investigate whether thyroid blocking should be limited to younger patients. This risk from the additional absorbed dose to the thyroid was then compared to the risk from iodine overdose through ingestion of the iodide prophylaxis, resulting in iodine-induced hyper/hypothyroidism (IIH). METHODS: A cohort of patients (n = 30) who did not receive thyroid prophylaxis underwent static thyroid imaging 3 h after 123 I-Ioflupane administration. The measured thyroidal uptake of free 123 I was then extrapolated to peak uptake time (24 h post-administration). This value was used to calculate cumulated activity in the thyroid and thus thyroid-thyroid absorbed dose D(rthy←rthy ) using the relevant S-value in the MIRD method. RESULTS: Mean D(rthy←rthy ) was found to be 13.6 mGy with an SD of 8.8 mGy; this would contribute an additional 0.5 mSv to the effective dose. CONCLUSION: ARSAC recommends in its Notes for Guidance prophylactic thyroid blocking if the absorbed dose to the thyroid is >50 mGy; the maximum thyroid dose in this study cohort was 36.3 mGy. With risk from IIH and its associated cardiac complications increasing with age, this study suggests that iodide prophylaxis with 123 I-Ioflupane should be reconsidered for elderly patient.

Modeling Overdispersed Dengue Data via Poisson Inverse Gaussian Regression Model: A Case Study in the City of Campo Grande, MS, Brazil.

Dengue fever is a tropical disease transmitted mainly by the female Aedes aegypti mosquito that affects millions of people every year. As there is still no safe and effective vaccine, currently the best way to prevent the disease is to control the proliferation of the transmitting mosquito. Since the proliferation and life cycle of the mosquito depend on environmental variables such as temperature and water availability, among others, statistical models are needed to understand the existing relationships between environmental variables and the recorded number of dengue cases and predict the number of cases for some future time interval. This prediction is of paramount importance for the establishment of control policies. In general, dengue-fever datasets contain the number of cases recorded periodically (in days, weeks, months or years). Since many dengue-fever datasets tend to be of the overdispersed, long-tail type, some common models like the Poisson regression model or negative binomial regression model are not adequate to model it. For this reason, in this paper we propose modeling a dengue-fever dataset by using a Poisson-inverse-Gaussian regression model. The main advantage of this model is that it adequately models overdispersed long-tailed data because it has a wider skewness range than the negative binomial distribution. We illustrate the application of this model in a real dataset and compare its performance to that of a negative binomial regression model.

Improving Abdominal Aortic Aneurysm (AAA) Screening Uptake through Patient Engagement-Analysis and Outcomes of Strategies to Improve Uptake at a Regional Program Level.

BACKGROUND: To identify areas of health inequality that adversely affect patient engagement at a regional level within the National Abdominal Aortic Aneurysm Screening Program (NAAASP). Patient-reported improvements to services were implemented and analysis of subsequent uptake undertaken. METHODS: A prospective study of 390 men who failed to attend their AAA screening invitation. Nonattendees were contacted by post and telephone. Patients were analyzed as per ethnicity, working status, and Index of Multiple Deprivation quintile. Patient-suggested improvements to the service were recorded, analyzed, and implemented. Uptake data were then collected for the subsequent two years. RESULTS: The Screening Management and Referral Tracking system used by NAAASP is 97% accurate in holding patient contact details, and nonattenders are four times more likely to respond to telephone contact. Reasons for failing to attend screening invitations include factors that can be addressed at a regional level such as: inconvenient timings/locations of screening clinics and a lack of awareness or understanding of what AAA screening means as well as language/literacy barriers. The incidence of AAAs in the nonattendee group was almost 3 times that of our general (attending) population. Afro-Caribbean men were disproportionately less likely to attend for screening. After implementing patient-suggested improvements to the service, screening uptake increased from 75.2% (2015-16 screening year) to 81.3% (2017-2018). CONCLUSIONS: To date, no other studies have gone on to assess the effectiveness of interventions targeted at reducing inequalities in NAAASP attendance, but we show an increase in local screening uptake of 6% in a 2-year period after implementing improvement strategies. This article adds to existing literature by confirming external factors such as social deprivation adversely influence screening uptake and that AAAs are more prevalent in socially deprived groups. It reinforces the importance of regional attempts to contact and engage nonattenders as they may be most at risk of developing AAAs.

Optimized robust plasma sampling for glomerular filtration rate studies.

In the presence of abnormal fluid collection (e.g. ascites), the measurement of glomerular filtration rate (GFR) based on a small number (1-4) of plasma samples fails. This study investigated how a few samples will allow adequate characterization of plasma clearance to give a robust and accurate GFR measurement. A total of 68 nine-sample GFR tests (from 45 oncology patients) with abnormal clearance of a glomerular tracer were audited to develop a Monte Carlo model. This was used to generate 20 000 synthetic but clinically realistic clearance curves, which were sampled at the 10 time points suggested by the British Nuclear Medicine Society. All combinations comprising between four and 10 samples were then used to estimate the area under the clearance curve by nonlinear regression. The audited clinical plasma curves were all well represented pragmatically as biexponential curves. The area under the curve can be well estimated using as few as five judiciously timed samples (5, 10, 15, 90 and 180 min). Several seven-sample schedules (e.g. 5, 10, 15, 60, 90, 180 and 240 min) are tolerant to any one sample being discounted without significant loss of accuracy or precision. A research tool has been developed that can be used to estimate the accuracy and precision of any pattern of plasma sampling in the presence of 'third-space' kinetics. This could also be used clinically to estimate the accuracy and precision of GFR calculated from mistimed or incomplete sets of samples. It has been used to identify optimized plasma sampling schedules for GFR measurement.

Totally implantable venous access devices - 20 years' experience of implantation in cystic fibrosis patients.

INTRODUCTION: Totally implantable venous access devices (TIVADs) are widely used to provide long-term, central venous access for antibiotic delivery in cystic fibrosis patients. However, few studies have demonstrated long-term follow-up with large cohorts. PATIENTS AND METHODS: This is a retrospective review of TIVADs implanted in cystic fibrosis patients by vascular surgeons at a tertiary referral centre, using an open venous cut-down technique, from March 1986 to July 2006. The cephalic vein was preferentially chosen for line placement, in the deltopectoral groove, under fluoroscopic control. TIVAD performance (life-span or survival) and complications were evaluated. Data were extracted by review of a local database (data collated prospectively since 1986), with supplementation from electronic patient records and medical notes. RESULTS: In total 165 TIVADs in 109 patients (34 males, 75 females) were reviewed. Median survival was 1441 days (range, 6-4440 days). Cumulative patency was 146,072 catheter-days. No immediate intrathoracic complications (pneumothorax, haemothorax, nerve injury) occurred. There were 3 early and 82 late complications, namely: occlusion (33 TIVADs; median age 510 days), infection (23 TIVADs; median 376 days), leakage (16; median 283 days), pain or discomfort (6), venous thrombosis (5), extravasation/skin necrosis (1), vegetation in right atrium (1). Overall incidence of complications was 0.58 per 1000 catheter-days. CONCLUSIONS: This study concurs with others that TIVADs are safe and effective, with a favourable life-span in cystic fibrosis patients if well looked after in a specialist centre. Complications of infection, leakage and occlusion do occur. Using an open, venous cut-down technique with fluoroscopic control avoids any immediate intrathoracic complications.