Community-level social determinants of health and pregestational and gestational diabetes

BACKGROUND

Individual adverse social determinants of health are associated with increased risk of diabetes in pregnancy, but the relative influence of neighborhood or community-level social determinants of health is unknown.

OBJECTIVE

This study aimed to determine whether living in neighborhoods with greater socioeconomic disadvantage, food deserts, or less walkability was associated with having pregestational diabetes and developing gestational diabetes.

STUDY DESIGN

We conducted a secondary analysis of the prospective Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-To-Be. Home addresses in the first trimester were geocoded at the census tract level. The exposures (modeled separately) were the following 3 neighborhood-level measures of adverse social determinants of health: (1) socioeconomic disadvantage, defined by the Area Deprivation Index and measured in tertiles from the lowest tertile (ie, least disadvantage [T1]) to the highest (ie, most disadvantage [T3]); (2) food desert, defined by the United States Department of Agriculture Food Access Research Atlas (yes/no by low income and low access criteria); and (3) less walkability, defined by the Environmental Protection Agency National Walkability Index (most walkable score [15.26-20.0] vs less walkable score [<15.26]). Multinomial logistic regression was used to model the odds of gestational diabetes or pregestational diabetes relative to no diabetes as the reference, adjusted for age at delivery, chronic hypertension, Medicaid insurance status, and low household income (<130% of the US poverty level).

RESULTS

Among the 9155 assessed individuals, the mean Area Deprivation Index score was 39.0 (interquartile range, 19.0-71.0), 37.0% lived in a food desert, and 41.0% lived in a less walkable neighborhood. The frequency of pregestational and gestational diabetes diagnosis was 1.5% and 4.2%, respectively. Individuals living in a community in the highest tertile of socioeconomic disadvantage had increased odds of entering pregnancy with pregestational diabetes compared with those in the lowest tertile (T3 vs T1: 2.6% vs 0.8%; adjusted odds ratio, 2.52; 95% confidence interval, 1.41-4.48). Individuals living in a food desert (4.8% vs 4.0%; adjusted odds ratio, 1.37; 95% confidence interval, 1.06-1.77) and in a less walkable neighborhood (4.4% vs 3.8%; adjusted odds ratio, 1.33; 95% confidence interval, 1.04-1.71) had increased odds of gestational diabetes. There was no significant association between living in a food desert or a less walkable neighborhood and pregestational diabetes, or between socioeconomic disadvantage and gestational diabetes.

CONCLUSION

Nulliparous individuals living in a neighborhood with higher socioeconomic disadvantage were at increased odds of entering pregnancy with pregestational diabetes, and those living in a food desert or a less walkable neighborhood were at increased odds of developing gestational diabetes, after controlling for known covariates.

Association between glycemic control and group B streptococcus colonization among pregnant individuals with pregestational diabetes

PROBLEM

Pregestational diabetes increases the risk of group B streptococcus (GBS) colonization in pregnancy. Whether glycemic control is associated with differences in this risk is unknown. We examined the association between glycemic control and GBS colonization among pregnant individuals with pregestational diabetes.

METHOD OF STUDY

A retrospective cohort of pregnant individuals with pregestational diabetes at a tertiary care center. The exposure was glycemic control, measured as hemoglobin A1c (A1c) at >20 weeks and assessed categorically at thresholds of <6.5% and <6.0%, and secondarily, as a continuous percentage. The outcome was maternal GBS colonization. Multivariable logistic regression was used and adjusted for age, parity, race, and ethnicity as a social determinant, body mass index, type of diabetes, and gestational age at A1c assessment.

RESULTS

Among 305 individuals (33% Type 1, 67% type 2), 45.0% (n = 140) were colonized with GBS. Individuals with an A1c < 6.5% were half as likely to be colonized with GBS compared with those with a A1c ≥ 6.5% (38.8% vs. 53.9%; adjusted odds ratio, AOR: 0.55; 95% CI: 0.33-0.91). Results were unchanged at an A1c threshold of <6.0% (35.7% vs. 48.5%; AOR: 0.60; 95% CI: 0.36-0.98). Individuals with a higher A1c as a continuous measure (%) were more likely to be colonized (AOR: 1.57 per 1%; 95% CI: 1.25-1.97).

CONCLUSIONS

Pregnant individuals with pregestational diabetes with worse glycemic control were at an increased risk of GBS colonization. Further study is needed to understand if improved glycemic control leads to lower risk of GBS colonization.

Challenges in Conducting Therapeutic Trials in Pregnancy: Emphasizing Recent Lessons Learned

Pregnant people have traditionally been excluded from therapeutic research by restrictions intended for fetal protection. Despite a movement toward inclusion, concerns for the feasibility and safety of including pregnant people in studies continue to limit this research. This article reviews the history of research guidelines in pregnancy and illustrates ongoing challenges, as seen in the development of vaccines and therapies during the coronavirus disease 2019 pandemic and investigation of statins for preeclampsia prevention. It explores new approaches that may be used to improve therapeutic research in pregnancy. A major cultural shift is needed to balance potential maternal and/or fetal risks with potential benefits from participation in research, as well as harm from withholding treatment or providing one that is not evidence-based. Finally, it is important to honor maternal autonomy in decision-making regarding participation in clinical trials.

Association of community walkability and glycemic control among pregnant individuals with pregestational diabetes mellitus

BACKGROUND

Neighborhood walkability is a community-level social determinant of health that measures whether people who live in a neighborhood walk as a mode of transportation. Whether neighborhood walkability is associated with glycemic control among pregnant individuals with pregestational diabetes remains to be defined.

OBJECTIVE

This study aimed to evaluate the association between community-level neighborhood walkability and glycemic control as measured by hemoglobin A1c (A1C) among pregnant individuals with pregestational diabetes.

STUDY DESIGN

This was a retrospective analysis of pregnant individuals with pregestational diabetes enrolled in an integrated prenatal and diabetes care program from 2012 to 2016. Participant addresses were geocoded and linked at the census-tract level. The exposure was community walkability, defined by the US Environmental Protection Agency National Walkability Index (score range 1-20), which incorporates intersection density (design), proximity to transit stops (distance), and a mix of employment and household types (diversity). Individuals from neighborhoods that were the most walkable (score, 15.26-20.0) were compared with those from neighborhoods that were less walkable (score <15.26), as defined per national Environmental Protection Agency recommendations. The outcomes were glycemic control, including A1C <6.0% and <6.5%, measured both in early and late pregnancy, and mean change in A1C across pregnancy. Modified Poisson regression and linear regression were used, respectively, and adjusted for maternal age, body mass index at delivery, parity, race and ethnicity as a social determinant of health, insurance status, baseline A1C, gestational age at A1C measurement in early and late pregnancy, and diabetes type.

RESULTS

Among 417 pregnant individuals (33% type 1, 67% type 2 diabetes mellitus), 10% were living in the most walkable communities. All 417 individuals underwent A1C assessment in early pregnancy (median gestational age, 9.7 weeks; interquartile range, 7.4-14.1), and 376 underwent another A1C assessment in late pregnancy (median gestational age, 30.4 weeks; interquartile range, 27.8-33.6). Pregnant individuals living in the most walkable communities were more likely to have an A1C <6.0% in early pregnancy (15% vs 8%; adjusted relative risk, 1.46; 95% confidence interval, 1.00-2.16), and an A1C <6.5% in late pregnancy compared with those living in less walkable communities (13% vs 9%; adjusted relative risk, 1.33; 95% confidence interval, 1.08-1.63). For individuals living in the most walkable communities, the median A1C was 7.5 (interquartile range, 6.0-9.4) in early pregnancy and 5.9 (interquartile range, 5.4-6.4) in late pregnancy. For those living in less walkable communities, the median A1C was 7.3 (interquartile range, 6.2-9.2) in early pregnancy and 6.2 (interquartile range, 5.6-7.1) in late pregnancy. Change in A1C across pregnancy was not associated with walkability.

CONCLUSION

Pregnant individuals with pregestational diabetes mellitus living in more walkable communities had better glycemic control in both early and late pregnancy. Whether community-level interventions to enhance neighborhood walkability can improve glycemic control in pregnancy requires further study.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

Implementation and Initial Construct Validity Evidence of a Tool, myTIPreport, for Interactive Workplace Feedback on ACGME Milestones

OBJECTIVE

To describe implementation of myTIPreport for milestone feedback and to initiate construct validity testing of myTIPreport for milestones.

DESIGN

myTIPreport was used to provide workplace feedback on Accreditation Council for Graduate Medical Education required milestone sets. Performance of senior learners (postgraduate year [PGY]-4s) was compared to that of junior learners (PGY-1s) to begin the process of construct validity testing for myTIPreport.

SETTING

A convenience-based site selection of Obstetrics and Gynecology (OBGYN) residency programs.

PARTICIPANTS

OBGYN residents and faculty.

RESULTS

Amongst the 12 participating OBGYN residency programs, there were 444 unique learners and 343 unique faculty teachers. A total of 5293 milestone feedback encounters were recorded. Mean PGY-4 performance was rated higher than mean PGY-1 performance on all 25 of the compared milestone sets, with statistically significant differences seen for 19 (76%) of these 25 milestone sets and nonsignificant differences in the predicted direction observed for the other 6 milestone sets.

CONCLUSIONS

myTIPreport detected differences between senior and junior learners for the majority of compared feedback encounters for OBGYN residents. Findings support the emerging construct validity of myTIPreport for milestone feedback.

Predicting changes in the status of patient-reported outcome measures after Birmingham Hip Resurfacing: an observational cohort study with a median follow-up of ten years

AIMS

It is not known whether change in patient-reported outcome measures (PROMs) over time can be predicted by factors present at surgery, or early follow-up. The aim of this study was to identify factors associated with changes in PROM status between two-year evaluation and medium-term follow-up.

PATIENTS AND METHODS

Patients undergoing Birmingham Hip Resurfacing completed the Veteran's Rand 36 (VR-36), modified Harris Hip Score (mHHS), Tegner Activity Score, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at two years and a minimum of three years. A change in score was assessed against minimal clinically important difference (MCID) and patient-acceptable symptom state (PASS) thresholds. Binary logistic regression was used to assess the relationship between patient factors and deterioration in PASS status between follow-ups.

RESULTS

Overall, 18% of patients reported reductions in mHHS total score exceeding MCID, and 21% reported similar reductions for WOMAC function scores. Nonetheless, almost all patients remained above PASS thresholds for WOMAC function (98%) and mHHS (93%). Overall, 66% of patients with mHHS scores < PASS at two years reported scores > PASS at latest follow-up. Conversely, 6% of patients deteriorated from > PASS to < PASS between follow-ups. Multivariable modelling indicated body mass index (BMI) > 27 kg/m², VR-36 Physical Component Score (PCS) < 51, VR-36 Mental Component Score (MCS) > 55, mHHS < 84 at two years, female sex, and bone graft use predicted these deteriorating patients with 79% accuracy and an area under the curve (AUC) of 0.84.

CONCLUSION

Due to largely acceptable results at a later follow-up, extensive monitoring of multiple PROMs is not recommended for Birmingham Hip Resurfacing patients unless they report borderline or unacceptable hip function at two years, are female, are overweight, or received a bone graft during surgery. Cite this article: Bone Joint J 2019;101-B:1431-1437.

The outcome and survival of metal-on-metal hip resurfacing in patients aged less than 50 years

Aims

The aim of this study was to report the implant survival and patient-reported outcome measures (PROMs) in a consecutive series of patients aged less than 50 years at the time of arthroplasty using the Birmingham Hip Resurfacing system (BHR), with a minimum follow-up of ten years.

Patients and Methods

A total of 226 patients with osteoarthritis of the hip, who underwent BHR and presented to a single surgeon, were included in the study. Survival of the implant was confirmed by cross-checking with the Australian Orthopaedic Association National Joint Replacement Registry. Kaplan–Meier survival curves with 95% confidence intervals (CIs) were constructed. Pre- and postoperative PROMs were compared with t-tests, and postoperative scores were compared using anchor analysis with age and gender matched normative data.

Results

At median follow-up of 12 years (interquartile range (IQR) 10 to 13), six BHRs were revised, with a cumulative rate of survival of 96.8% (95% confidence interval (CI) 94.2 to 99.4) at 15 years, and with a significantly lower (p = 0.019) cumulative rate of revision than the national average for the same device at ten years. Most revisions (n = 4) were undertaken early, less than three years postoperatively, and occurred in women. Patient-reported general health (Veteran’s Rand-36), disease state (Western Ontario and McMaster Universities Osteoarthritis Index), function (modified Harris Hip Score) and level of activity (Tegner activity score) maintained significant (p < 0.01 for each) improvements beyond ten years postoperatively and were equal to, or exceeded, age- and gender-matched normative data in more than 80% of the patients.

Conclusion

Longer term PROMs after BHR, from a single surgeon, for patients aged less than 50 years remain under-reported. We found that the outcome after a BHR, at a minimum of ten years postoperatively, remained satisfactory, particularly for self-reported hip function.

Acute toxicity of hypofractionated intensity-modulated radiotherapy for prostate cancer

BACKGROUND

Dose-escalated hypofractionated radiotherapy (hfrt) using intensity-modulated radiotherapy (imrt), with inclusion of the pelvic lymph nodes (plns), plus androgen suppression therapy (ast) in high-risk prostate cancer patients should improve patient outcomes, but acute toxicity could limit its feasibility.

METHODS

Our single-centre phase ii prospective study enrolled 40 high-risk prostate cancer patients. All patients received hfrt using imrt with daily mega-voltage computed tomography imaging guidance, with 95% of planning target volumes (ptv68 and ptv50) receiving 68 Gy and 50 Gy (respectively) in 25 daily fractions. The boost volume was targeted to the involved plns and the prostate (minus the urethra plus 3 mm and minus 3 mm from adjacent rectal wall) and totalled up to 75 Gy in 25 fractions. Acute toxicity scores were recorded weekly during and 3 months after radiotherapy (rt) administration.

RESULTS

For the 37 patients who completed rt and the 3-month follow-up, median age was 65.5 years (range: 50-76 years). Disease was organ-confined (T1c-T2c) in 23 patients (62.1%), and node-positive in 5 patients (13.5%). All patients received long-term ast. Maximum acute genitourinary (gu) and gastrointestinal (gi) toxicity peaked at grade 2 in 6 of 36 evaluated patients (16.6%) and in 4 of 31 evaluated patients (12.9%) respectively. Diarrhea and urinary frequency were the chief complaints. Dose-volume parameters demonstrated no correlation with toxicity. The ptv treatment objectives were met in 36 of the 37 patients.

CONCLUSIONS

This hfrt dose-escalation trial in high-risk prostate cancer has demonstrated the feasibility of administering 75 Gy in 25 fractions with minimal acute gi and gu toxicities. Further follow-up will report late toxicities and outcomes.

Experimental demonstration of a soft x-ray self-seeded free-electron laser

The Linac Coherent Light Source has added a self-seeding capability to the soft x-ray range using a grating monochromator system. We report the demonstration of soft x-ray self-seeding with a measured resolving power of 2000-5000, wavelength stability of 10(-4), and an increase in peak brightness by a factor of 2-5 across the photon energy range of 500-1000 eV. By avoiding the need for a monochromator at the experimental station, the self-seeded beam can deliver as much as 50-fold higher brightness to users.

Analysis of intraprostatic therapeutic effects in prostate cancer patients using [(11)C]-choline pet/ct after external-beam radiation therapy

PURPOSE

The objective of the present study was to analyze, with relatively high sensitivity and specificity, uptake properties of [(11)C]-choline in prostate cancer patients by means of positron-emission tomography (pet)/computed tomography (ct) imaging using objectively defined pet parameters to test for statistically significant changes before, during, and after external-beam radiation therapy (ebrt) and to identify the time points at which the changes occur.

METHODS

The study enrolled 11 patients with intermediate-risk prostate cancer treated with ebrt, who were followed for up to 12 months after ebrt. The [(11)C]-choline pet scans were performed before treatment (baseline); at weeks 4 and 8 of ebrt; and at 1, 2, 3, 6, and 12 months after ebrt.

RESULTS

Analysis of [(11)C]-choline uptake in prostate tissue before treatment resulted in a maximum standardized uptake value (suvmax) of 4.0 ± 0.4 (n = 11) at 40 minutes after injection. During week 8 of ebrt, the suvmax declined to 2.9 ± 0.1 (n = 10, p < 0.05). At 2 and 12 months after ebrt, suvmax values were 2.3 ± 0.3 (n = 10, p < 0.01) and 2.2 ± 0.2 (n = 11, p < 0.001) respectively, indicating that, after ebrt, maximum radiotracer uptake in the prostate was significantly reduced. Similar effects were observed when analyzing the tumour:muscle ratio (tmr). The tmr declined from 7.4 ± 0.6 (n = 11) before ebrt to 6.1 ± 0.4 (n = 11, nonsignificant) during week 8 of ebrt, to 5.6 ± 0.03 (n = 11, p < 0.05) at 2 months after ebrt, and to 4.4 ± 0.4 (n = 11, p < 0.001) at 12 months after ebrt.

CONCLUSIONS

Our study demonstrated that intraprostatic [(11)C]-choline uptake in the 11 analyzed prostate cancer patients significantly declined during and after ebrt. The pet parameters SUVmax and tmr also declined significantly. These effects can be detected during radiation therapy and up to 1 year after therapy. The prognostic value of these early and statistically significant changes in intraprostatic [(11)C]-choline pet avidity during and after ebrt are not yet established. Future studies are indicated to correlate changes in [(11)C]-choline uptake parameters with long-term biochemical recurrence to further evaluate [(11)C]-choline pet changes as a possible, but currently unproven, biomarker of response.

Femtosecond x-ray pulse characterization in free-electron lasers using a cross-correlation technique

We report the first measurements of x-ray single-pulse duration and two-pulse separation at the Linac Coherent Light Source using a cross-correlation technique involving x rays and electrons. An emittance-spoiling foil is adopted as a very simple and effective method to control the output x-ray pulse. A minimum pulse duration of about 3 fs full width at half maximum has been measured together with a controllable pulse separation (delay) between two pulses. This technique provides critical temporal diagnostics for x-ray experiments such as x-ray pump-probe studies.

Porcine urinary bladder matrix: a retrospective study and establishment of protocol

OBJECTIVE

To summarise our experience with porcine urinary bladder matrix extracellular matrix (UBM) for the treatment of diabetic, venous, ischaemic or decubitus ulcerations and to outline appropriate protocol for its application.

METHOD

A retrospective review was also conducted on all patients who received UBM (MatriStem; A Cell, Inc.) from January to December 201 I. Information regarding patient demographics, wound aetiology and location, as well as any prior treatments and follow-up data,were collected and reviewed from patients' medical records.

RESULTS

Thirty-four patients were evaluated for this study. Mean patient age was 62.4 + 13.4 years (range 29-88 years) and 76% (n = 26) were male.The most common comorbidities were peripheral neuropathy (n = 20), diabetes mellitus type 2 (n = 19) and hypertension (n= 13). Mean wound duration prior to UBM application was 25.5 43.5 weeks, and mean time to healing following initial application was 9.8 9.3 weeks. All patients treated with UBM progressed to full healing.

CONCLUSION

After addressing modifiable risk factors, our study suggests UBM is effective in the treatment of acute and recalcitrant diabetic or venous ulcerations when applied correctly with an appropriate dressing.

DECLARATION OF INTEREST

There were no external sources of funding for this study.The authors have no conflicts of interest to declare.

Search for a new gauge boson in electron-nucleus fixed-target scattering by the APEX experiment

We present a search at the Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling α' to electrons. Such a particle A' can be produced in electron-nucleus fixed-target scattering and then decay to an e + e- pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175-250 MeV, found no evidence for an A'→ e+ e- reaction, and set an upper limit of α'/α ~/= 10(-6). Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.

Estimates of length of neonatal stay for very premature babies in the UK

OBJECTIVE

To describe simple estimates of likely duration of stay for very premature babies born in the UK and discharged home.

DESIGN

Statistical modelling of data from thirty neonatal units in a geographically defined region of the UK.

PARTICIPANTS

All babies born at 23 to 32 completed weeks of gestation in 2005, 2006 and 2007 who were discharged home with the expectation that they would survive.

MAIN OUTCOME MEASURE

Total duration of stay in the neonatal service.

RESULTS

5528 babies were initially identified. 558 (10.1%) who died or who did not follow a normal care pathway were excluded. In a further 27, data were either missing or inadequate, leaving a study population of 4702 babies. As expected, gestation and birthweight exhibited strong influence on length of stay. Of the other variables tested, initial reason for admission (need for early respiratory support) showed the most consistent association. These factors were combined to produce predictive tables. The predictive performance of the tables was found to fit the data well for various groups, with the exception of multiple births who tended to have longer stays. However, when tested against individual units, much greater variation was seen independent of unit size and case mix.

CONCLUSION

The prediction tables should permit parents to make sensible estimates about the duration of their baby's stay in the neonatal service; however, there appear to be important differences between units. The variation noted in length of stay between otherwise similar units merits further investigation.

Environmental controls on stomatal conductance in a shrub of the humid tropics

Leaves of Piper hispidum, a shrub native to the lowland tropics of Mexico, have a strong stomatal response to humidity that results in similar rates of water loss under a wide range of leaf-to-air water-vapor concentration gradients. Stomatal conductance of these leaves is insensitive to CO(2) concentration and increases in response to high humidity even in the dark.

Relative biological damage and electron fluence in and out of a 6 MV photon field

Scattered radiation in the penumbra of a megavoltage radiation therapy beam can deposit a non-negligible dose in the healthy tissue around a target volume. The lower energy of the radiation in this region suggests that its biological effectiveness might not be the same as that of the open beam. In this work, we determined the relative biological damage in normal human fibroblasts after megavoltage irradiation in two geometries. The first was an open-beam irradiation and the second was a blocked configuration in which only scattered radiation could reach the target cells. The biological damage was evaluated by the gamma-H2AX immunofluorescence assay, which is capable of detecting DNA double-strand breaks in individual cells. We report that the scattered radiation is more effective at producing biological damage than the open beam radiation. We found a 27% enhancement in the net mean nuclear gamma-H2AX fluorescence intensity at 2 Gy and a 48% enhancement at 4 Gy. These findings are of interest due to the increased doses of penumbral radiation close to target volumes both in dose escalation studies and in IMRT treatment deliveries where high dose gradients exist for the purpose of conformal avoidance of healthy tissues.

Estimation of renal function -- what is appropriate in cancer patients?

AIMS

To compare the accuracy of renal assessment in patients with cancer using radioisotope glomerular filtration rate (GFR), urine collection for creatinine clearance, Cockroft-Gault, Modification of Diet in Renal Disease (MDRD) and Wright formulae.

MATERIALS AND METHODS

Measurements of isotope GFR from 367 patients were compared with estimates from the described methods (Cockroft-Gault, MDRD, Wright). An analysis including a further 252 patients with an isotope GFR < or = 50 ml/min was also carried out.

RESULTS

The Wright formula was the most accurate form of estimating renal function for the first study group. The formulae were similar in accuracy in the second study group.

CONCLUSIONS

The Wright formula is the most accurate form of estimation of renal function in comparison with the isotope GFR for cancer patients. When there is a large proportion of patients with a low isotope GFR (< or = 50 ml/min), the formulae have similar accuracy.

A Monte Carlo study of the variation of electron fluence in water from a 6 MV photon beam outside of the field

Existing studies have suggested some debate on whether the quality of radiation that delivers dose outside of the primary field of a radiotherapy photon beam can be considered the same as that inside the primary field. We used a Monte Carlo approach to simulate the electron fluence differential in energy inside a water phantom in response to irradiation by a 6 MV photon beam. The goal was to quantify how significantly the electron fluence changes when moving from a volume exposed to the primary field to one outside of the primary field, and understand any potential biological implications. We scored the electron fluence outwards in annular volumes in response to a 5 cm radius 6 MV beam and at the central axis in response to a rectangular 6 MV beam partially blocked by an MLC. The resulting fluence spectra were compared to different low-LET sources for which biological response in the form of chromosomal aberrations has been published. Our results show a significant increase in the low energy component of the fluence spectra outside of the primary field, which increases the mean LET to values similar to that seen in response to a 137Cs photon source. In turn, it is shown that this has the potential to increase the RBE.

Longitudinal variable selection by cross-validation in the case of many covariates

Longitudinal models are commonly used for studying data collected on individuals repeatedly through time. While there are now a variety of such models available (marginal models, mixed effects models, etc.), far fewer options exist for the closely related issue of variable selection. In addition, longitudinal data typically derive from medical or other large-scale studies where often large numbers of potential explanatory variables and hence even larger numbers of candidate models must be considered. Cross-validation is a popular method for variable selection based on the predictive ability of the model. Here, we propose a cross-validation Markov chain Monte Carlo procedure as a general variable selection tool which avoids the need to visit all candidate models. Inclusion of a 'one-standard error' rule provides users with a collection of good models as is often desired. We demonstrate the effectiveness of our procedure both in a simulation setting and in a real application.

Evolution of sensory complexity recorded in a myxobacterial genome

Myxobacteria are single-celled, but social, eubacterial predators. Upon starvation they build multicellular fruiting bodies using a developmental program that progressively changes the pattern of cell movement and the repertoire of genes expressed. Development terminates with spore differentiation and is coordinated by both diffusible and cell-bound signals. The growth and development of Myxococcus xanthus is regulated by the integration of multiple signals from outside the cells with physiological signals from within. A collection of M. xanthus cells behaves, in many respects, like a multicellular organism. For these reasons M. xanthus offers unparalleled access to a regulatory network that controls development and that organizes cell movement on surfaces. The genome of M. xanthus is large (9.14 Mb), considerably larger than the other sequenced delta-proteobacteria. We suggest that gene duplication and divergence were major contributors to genomic expansion from its progenitor. More than 1,500 duplications specific to the myxobacterial lineage were identified, representing >15% of the total genes. Genes were not duplicated at random; rather, genes for cell-cell signaling, small molecule sensing, and integrative transcription control were amplified selectively. Families of genes encoding the production of secondary metabolites are overrepresented in the genome but may have been received by horizontal gene transfer and are likely to be important for predation.