Extracting the normal lung dose-response curve from clinical DVH data: a possible role for low dose hyper-radiosensitivity, increased radioresistance

In conventionally fractionated radiation therapy for lung cancer, radiation pneumonitis' (RP) dependence on the normal lung dose-volume histogram (DVH) is not well understood. Complication models alternatively make RP a function of a summary statistic, such as mean lung dose (MLD). This work searches over damage profiles, which quantify sub-volume damage as a function of dose. Profiles that achieve best RP predictive accuracy on a clinical dataset are hypothesized to approximate DVH dependence.Step function damage rate profiles R(D) are generated, having discrete steps at several dose points. A range of profiles is sampled by varying the step heights and dose point locations. Normal lung damage is the integral of R(D) with the cumulative DVH. Each profile is used in conjunction with a damage cutoff to predict grade 2 plus (G2+) RP for DVHs from a University of Michigan clinical trial dataset consisting of 89 CFRT patients, of which 17 were diagnosed with G2+ RP.Optimal profiles achieve a modest increase in predictive accuracy--erroneous RP predictions are reduced from 11 (using MLD) to 8. A novel result is that optimal profiles have a similar distinctive shape: enhanced damage contribution from low doses (<20 Gy), a flat contribution from doses in the range ~20-40 Gy, then a further enhanced contribution from doses above 40 Gy. These features resemble the hyper-radiosensitivity / increased radioresistance (HRS/IRR) observed in some cell survival curves, which can be modeled using Joiner's induced repair model.A novel search strategy is employed, which has the potential to estimate RP dependence on the normal lung DVH. When applied to a clinical dataset, identified profiles share a characteristic shape, which resembles HRS/IRR. This suggests that normal lung may have enhanced sensitivity to low doses, and that this sensitivity can affect RP risk.

Reliable detection of fluence anomalies in EPID-based IMRT pretreatment quality assurance using pixel intensity deviations

PURPOSE

This work uses repeat images of intensity modulated radiation therapy (IMRT) fields to quantify fluence anomalies (i.e., delivery errors) that can be reliably detected in electronic portal images used for IMRT pretreatment quality assurance.

METHODS

Repeat images of 11 clinical IMRT fields are acquired on a Varian Trilogy linear accelerator at energies of 6 MV and 18 MV. Acquired images are corrected for output variations and registered to minimize the impact of linear accelerator and electronic portal imaging device (EPID) positioning deviations. Detection studies are performed in which rectangular anomalies of various sizes are inserted into the images. The performance of detection strategies based on pixel intensity deviations (PIDs) and gamma indices is evaluated using receiver operating characteristic analysis.

RESULTS

Residual differences between registered images are due to interfraction positional deviations of jaws and multileaf collimator leaves, plus imager noise. Positional deviations produce large intensity differences that degrade anomaly detection. Gradient effects are suppressed in PIDs using gradient scaling. Background noise is suppressed using median filtering. In the majority of images, PID-based detection strategies can reliably detect fluence anomalies of ≥5% in ∼1 mm(2) areas and ≥2% in ∼20 mm(2) areas.

CONCLUSIONS

The ability to detect small dose differences (≤2%) depends strongly on the level of background noise. This in turn depends on the accuracy of image registration, the quality of the reference image, and field properties. The longer term aim of this work is to develop accurate and reliable methods of detecting IMRT delivery errors and variations. The ability to resolve small anomalies will allow the accuracy of advanced treatment techniques, such as image guided, adaptive, and arc therapies, to be quantified.

SU-F-BRCD-06: Multiple Anatomy Optimization of Accumulated Dose

PURPOSE

Multiple anatomy optimization (MAO) utilizing deformable dose accumulation on entire 4DCT data sets is implemented to overcome ambiguity between optimal dose defined on a single anatomy and optimal accumulated dose resulting from dose delivery to moving and deforming anatomy.

METHODS

Six lung cancer patients are planned using two methods of radiotherapy optimization: the internal target volume (ITV) envelope method and MAO, which simultaneously optimizes a single fluence for delivery to all 10 breathing phases such that the accumulated dose satisfies the plan objectives. Target dose is constrained to 70 Gy. The ITV-plan is optimized on a single breathing phase with the planning target volume defined as the ITV; the MAO target is the moving CTV. MAO is compared to single image ITV optimization based on the accumulated dose assuming equal monitor-units to each phase. Dose-volume differences between single image estimations and 10-image accumulation are examined.

RESULTS

Single image optimal dose distributions overestimate target V70 by 4.2%±3.1% (average, one standard deviation) and in five of six cases ipsilateral lung V20 is underestimated (1.4%±0.9%). For these five cases, MAO increases V70 by 2.8%±2.5% (maximum of 6% increase in V70) and reduces ipsilateral lung V20 by up to 3% (average decrease of 1.2%±1.3%). Contralateral lung V20, esophagus V25, and heart V30 are also reduced by up to 5%, 3%, and 3%. For the sixth case, lung tumor motion is on the order of the dose voxel size (3mm), and MAO did not improve upon the ITV plan.

CONCLUSIONS

Dose-volume optimization on a stationary image does not ensure accumulated dose coverage to the moving CTV. Multiple anatomy optimization can remove dose ambiguity and improve plan quality. P01CA11602 and Philips Medical Systems.

The effect of uterine motion and uterine margins on target and normal tissue doses in intensity modulated radiation therapy of cervical cancer

In intensity modulated radiation therapy (IMRT) of cervical cancer, uterine motion can be larger than cervix motion, requiring a larger clinical target volume to planning target volume (CTV-to-PTV) margin around the uterine fundus. This work simulates different motion models and margins to estimate the dosimetric consequences. A virtual study used image sets from ten patients. Plans were created with uniform margins of 1 cm (PTV(A)) and 2.4 cm (PTV(C)), and a margin tapering from 2.4 cm at the fundus to 1 cm at the cervix (PTV(B)). Three inter-fraction motion models (MM) were simulated. In MM1, all structures moved with normally distributed rigid body translations. In MM2, CTV motion was progressively magnified as one moved superiorly from the cervix to the fundus. In MM3, both CTV and normal tissue motion were magnified as in MM2, modeling the scenario where normal tissues move into the void left by the mobile uterus. Plans were evaluated using static and percentile DVHs. For a conventional margin (PTV(A)), quasi-realistic uterine motion (MM3) reduces fundus dose by about 5 Gy and increases normal tissue volumes receiving 30-50 Gy by ∼5%. A tapered CTV-to-PTV margin can restore fundus and CTV doses, but will increase normal tissue volumes receiving 30-50 Gy by a further ∼5%.

Coverage optimized planning: probabilistic treatment planning based on dose coverage histogram criteria

This work (i) proposes a probabilistic treatment planning framework, termed coverage optimized planning (COP), based on dose coverage histogram (DCH) criteria; (ii) describes a concrete proof-of-concept implementation of COP within the PINNACLE treatment planning system; and (iii) for a set of 28 prostate anatomies, compares COP plans generated with this implementation to traditional PTV-based plans generated with planning criteria approximating those in the high dose arm of the Radiation Therapy Oncology Group 0126 protocol. Let Dv denote the dose delivered to fractional volume v of a structure. In conventional intensity modulated radiation therapy planning, Dv has a unique value derived from the static (planned) dose distribution. In the presence of geometric uncertainties (e.g., setup errors) Dv assumes a range of values. The DCH is the complementary cumulative distribution function of D(v+). DCHs are similar to dose volume histograms (DVHs). Whereas a DVH plots volume v versus dose D, a DCH plots coverage probability Q versus D. For a given patient, Q is the probability (i.e., percentage of geometric uncertainties) for which the realized value of Dv exceeds D. PTV-based treatment plans can be converted to COP plans by replacing DVH optimization criteria with corresponding DCH criteria. In this approach, PTVs and planning organ at risk volumes are discarded, and DCH criteria are instead applied directly to clinical target volumes (CTVs) or organs at risk (OARs). Plans are optimized using a similar strategy as for DVH criteria. The specific implementation is described. COP was found to produce better plans than standard PTV-based plans, in the following sense. While target OAR dose tradeoff curves were equivalent to those for PTV-based plans, COP plans were able to exploit slack in OAR doses, i.e., cases where OAR doses were below their optimization limits, to increase target coverage. Specifically, because COP plans were not constrained by a predefined PTV, they were able to provide wider dosimetric margins around the CTV, by pushing OAR doses up to, but not beyond, their optimization limits. COP plans demonstrated improved target coverage when averaged over all 28 prostate anatomies, indicating that the COP approach can provide benefits for many patients. However, the degree to which slack OAR doses can be exploited to increase target coverage will vary according to the individual patient anatomy. The proof-of-concept COP implementation investigated here utilized a probabilistic DCH criteria only for the CTV minimum dose criterion. All other optimization criteria were conventional DVH criteria. In a mature COP implementation, all optimization criteria will be DCH criteria, enabling direct planning control over probabilistic dose distributions. Further research is necessary to determine the benefits of COP planning, in terms of tumor control probability and/or normal tissue complication probabilities.

Coverage-based treatment planning: optimizing the IMRT PTV to meet a CTV coverage criterion

This work demonstrates an iterative approach-referred to as coverage-based treatment planning-designed to produce treatment plans that ensure target coverage for a specified percentage of setup errors. In this approach the clinical target volume to planning target volume (CTV-to-PTV) margin is iteratively adjusted until the specified CTV coverage is achieved. The advantage of this approach is that it automatically compensates for the dosimetric margin around the CTV, i.e., the extra margin that is created when the dose distribution extends beyond the PTV. When applied to 27 prostate plans, this approach reduced the average CTV-to-PTV margin from 5 to 2.8 mm. This reduction in PTV size produced a corresponding decrease in the volume of normal tissue receiving high dose. The total volume of tissue receiving > or =65 Gy was reduced on average by 19.3% or about 48 cc. Individual reductions varied from 8.7% to 28.6%. The volume of bladder receiving > or =60 Gy was reduced on average by 5.6% (reductions for individuals varied from 1.7% to 10.6%), and the volume of periprostatic rectum receiving > or =65 Gy was reduced on average by 4.9% (reductions for individuals varied from 0.9% to 12.3%). The iterative method proposed here represents a step toward a probabilistic treatment planning algorithm which can generate dose distributions (i.e., treated volumes) that closely approximate a specified level of coverage in the presence of geometric uncertainties. The general principles of coverage-based treatment planning are applicable to arbitrary treatment sites and delivery techniques. Importantly, observed deviations between coverage implied by specified CTV-to-PTV margins and coverage achieved by a given treatment plan imply a generic need to perform coverage probability analysis on a per-plan basis to ensure that the desired level of coverage is achieved.

Evaluation of dosimetric margins in prostate IMRT treatment plans

This work introduces a new concept--the dosimetric margin distribution (DMD)--and uses it to explain the sensitivity of a group of prostate IMRT treatment plans to patient setup errors. Prior work simulated the effect of setup errors on 27 prostate IMRT treatment plans and found the plans could tolerate larger setup errors than predicted by the van Herk margin formula. The conjectured reason for this disagreement was a breakdown in van Herk's assumption that the planned dose distribution conforms perfectly to target structures. To resolve the disagreement, this work employed the same 27 plans to evaluate the actual margin distributions that exist between: (i) the clinical target volume (CTV) and planning target volume (PTV) and (ii) the CTV and PTV minimum dose isodose surface. These distributions were evaluated for both prostate and nodal targets. Distribution (ii) is the DMD. The dosimetric margin in a given direction determines the probability that the CTV will be underdosed due to setup errors in that direction. Averaging over 4 pi sr gives the overall probability of CTV coverage. Minimum doses for prostate and nodal PTVs were obtained from dose volume histograms. Corresponding isodose surfaces were created and converted to regions of interest (ROIs). CTV, PTV, and isodose ROIs were saved as mesh files and then imported into a computational geometry application which calculated distances between meshes (i.e., margins) in 614 discrete directions covering 4 pi sr in 10 deg increments. Measured prostate CTV-to-PTV margins were close to the nominal value of 0.5 cm specified in the treatment planning protocol. However, depending on direction, prostate dosimetric margins ranged from 0.5 to 3 cm, reflecting the imperfect conformance of the planned dose distribution to the prostate PTV. For the nodal CTV, the nominal CTV-to-PTV margin employed in treatment planning was again 0.5 cm. However, due to the planning protocol, the nodal PTV follows the surface of the nodal CTV in several places, ensuring that there is no room for rigid body motion of the nodal CTV inside the nodal PTV. Measured nodal CTV-to-PTV margins were therefore zero, while nodal dosimetric margins ranged from 0.2 to 2.8 cm. Prostate and nodal target coverage were found to be well correlated with the measured DMDs, thereby resolving the apparent disagreement with our prior results. The principal conclusion is that target coverage in the presence of setup errors should be evaluated using the DMD, rather than the CTV-to-PTV margin distribution. The DMD is a useful planning metric, which generalizes the ICRU conformity index. DMDs could vary with number of beams, beam arrangements, TPS, and treatment site.

Convolution method and CTV-to-PTV margins for finite fractions and small systematic errors

The van Herk margin formula (VHMF) relies on the accuracy of the convolution method (CM) to determine clinical target volume (CTV) to planning target volume (PTV) margins. This work (1) evaluates the accuracy of the CM and VHMF as a function of the number of fractions N and other parameters, and (2) proposes an alternative margin algorithm which ensures target coverage for a wider range of parameter values. Dose coverage was evaluated for a spherical target with uniform margin, using the same simplified dose model and CTV coverage criterion as were used in development of the VHMF. Systematic and random setup errors were assumed to be normally distributed with standard deviations Sigma and sigma. For clinically relevant combinations of sigma, Sigma and N, margins were determined by requiring that 90% of treatment course simulations have a CTV minimum dose greater than or equal to the static PTV minimum dose. Simulation results were compared with the VHMF and the alternative margin algorithm. The CM and VHMF were found to be accurate for parameter values satisfying the approximate criterion: sigma[1 - gammaN/25] < 0.2, where gamma = Sigma/sigma. They were found to be inaccurate for sigma[1 - gammaN/25] > 0.2, because they failed to account for the non-negligible dose variability associated with random setup errors. These criteria are applicable when sigma greater than or approximately egual sigma(P), where sigma(P) = 0.32 cm is the standard deviation of the normal dose penumbra. (Qualitative behaviour of the CM and VHMF will remain the same, though the criteria might vary if sigma(P) takes values other than 0.32 cm.) When sigma << sigma(P), dose variability due to random setup errors becomes negligible, and the CM and VHMF are valid regardless of the values of Sigma and N. When sigma greater than or approximately egual sigma(P), consistent with the above criteria, it was found that the VHMF can underestimate margins for large sigma, small Sigma and small N. A potential consequence of this underestimate is that the CTV minimum dose can fall below its planned value in more than the prescribed 10% of treatments. The proposed alternative margin algorithm provides better margin estimates and CTV coverage over the parameter ranges examined here. This algorithm is not amenable to expression as a simple formula (e.g., as a linear combination of Sigma and sigma). However, it can be easily calculated. For 0.1 cm < or = sigma < or = 0.75 cm, 0 < or = gamma < or = 1 and 5 < or = N < or = 30, the VHMF underestimates margins by as much as 33%. With the alternative margin algorithm, the maximum underestimate is 7%. These results suggest that the VHMF should be used with caution for hypofractionated treatment and in adaptive therapy.

Evaluation of clinical margins via simulation of patient setup errors in prostate IMRT treatment plans

This work evaluates: (i) the size of random and systematic setup errors that can be absorbed by 5 mm clinical target volume (CTV) to planning target volume (PTV) margins in prostate intensity modulated radiation therapy (IMRT); (ii) agreement between simulation results and published margin recipes; and (iii) whether shifting contours with respect to a static dose distribution accurately predicts dose coverage due to setup errors. In 27 IMRT treatment plans created with 5 mm CTV-to-PTV margins, random setup errors with standard deviations (SDs) of 1.5, 3, 5 and 10 mm were simulated by fluence convolution. Systematic errors with identical SDs were simulated using two methods: (a) shifting the isocenter and recomputing dose (isocenter shift), and (b) shifting patient contours with respect to the static dose distribution (contour shift). Maximum tolerated setup errors were evaluated such that 90% of plans had target coverage equal to the planned PTV coverage. For coverage criteria consistent with published margin formulas, plans with 5 mm margins were found to absorb combined random and systematic SDs = 3 mm. Published recipes require margins of 8-10 mm for 3 mm SDs. For the prostate IMRT cases presented here a 5 mm margin would suffice, indicating that published recipes may be pessimistic. We found significant errors in individual plan doses given by the contour shift method. However, dose population plots (DPPs) given by the contour shift method agreed with the isocenter shift method for all structures except the nodal CTV and small bowel. For the nodal CTV, contour shift DPP differences were due to the structure moving outside the patient. Small bowel DPP errors were an artifact of large relative differences at low doses. Estimating individual plan doses by shifting contours with respect to a static dose distribution is not recommended. However, approximating DPPs is acceptable, provided care is taken with structures such as the nodal CTV which lie close to the surface.

Improved prediction of bacterial transcription start sites

MOTIVATION

Identifying bacterial promoters is an important step towards understanding gene regulation. In this paper, we address the problem of predicting the location of promoters and their transcription start sites (TSSs) in Escherichia coli. The accepted method for this problem is to use position weight matrices (PWMs), which define conserved motifs at the sigma-factor binding site. However this method is known to result in large numbers of false positive predictions.

RESULTS

Our approaches to TSS prediction are based upon an ensemble of support vector machines (SVMs) employing a variant of the mismatch string kernel. This classifier is subsequently combined with a PWM and a model based on distribution of distances from TSS to gene start. We investigate the effect of different scoring techniques and quantify performance using area under a detection-error tradeoff curve. When tested on a biologically realistic task, our method provides performance comparable with or superior to the best reported for this task. False positives are significantly reduced, an improvement of great significance to biologists.

AVAILABILITY

The trained ensemble-SVM model with instructions on usage can be downloaded from http://eresearch.fit.qut.edu.au/downloads

Prior academic background and student performance in assessment in a graduate entry programme

OBJECTIVES

This study aims to identify whether non-science graduates perform as well as science graduates in Basic and Clinical Sciences (B & CS) assessments during Years 1-3 of a four-year graduate-entry programme at the University of Sydney (the 'USydMP').

METHODS

Students were grouped into five categories: Health Professions (HP), Biomedical Sciences (BMS), Other Biology (BIOL), Physical Sciences (PHYS) or Non-Science (NONS). We examined the performance rank of students in each of the five groups for single best answer (SBA) and modified essay (MEQ) assessments separately, and also calculated the relative risk of failure in the summative assessments in Years 2 and 3.

RESULTS

Students with science-based prior degrees performed better in the SBA assessments. The same occurred initially in the MEQs, but the effect diminished with time. The HP students performed consistently better but converged with other groups over time, particularly in the MEQs. Relative performance by the NONS students improved with time in both assessment formats. Overall, differences between the highest and lowest groups were small and very few students failed to meet the overall standard for the summative assessments. HP and BMS students had the lowest failure rate. NONS students were more likely to fail the assessments in Year 2 and 3, but their pass rates were still high. Female students performed significantly better overall at the end of Year 2 and in Year 3. There were only minor differences between Australian resident and International students.

CONCLUSION

While there are small differences in performance in B & CS early in the programme, these lessen with time. The study results will inform decisions regarding timing of summative assessments, selection policy and for providing additional support to students who need it to minimize their risk of failure. Readers should note that this paper refers to student performance in only one of the four curriculum themes, where health professional and science graduates would be expected to have a significant advantage.

Benzodiazepine prescribing by GP registrars. A trial of educational outreach

BACKGROUND

Despite ongoing concern about adverse effects and dependence on benzodiazepines, approximately 2% of Australians are still taking them on a regular basis. The aim of this study was to evaluate the effectiveness of an educational outreach or 'academic detailing' program about prescribing of benzodiazepines.

METHOD

In this randomised trial general practice registrars (n = 157) in New South Wales were allocated to an intervention group (n = 79), which received a 20 minute educational outreach visit; or a control group (n = 78) which received an intervention on an unrelated topic. Prescribing behaviour was monitored by a pre-intervention and two post-intervention practice activity surveys.

MAIN OUTCOME MEASURES

These were the rate of benzodiazepine prescribing for all indications, for anxiety and for sleep disorders.

RESULTS

Overall benzodiazepine prescribing by the intervention group declined from 2.3 to 1.7 per 100 encounters, while the control group also declined from 2.2 to 1.6 per 100 encounters. Analysis of variance showed this was a significant drop over time (P = 0.042) but there was no difference between groups (P = 0.99). The prescribing decrease observed was in continuing rather than initial prescriptions.

CONCLUSIONS

A marked decrease in benzodiazepine prescribing was seen over the course of the study in both intervention and control groups but no differential effect due to the educational outreach visit was found.

Evaluation of an educational program in rational prescribing for GP trainees

Education on rational prescribing is receiving increased emphasis but the effectiveness of this education is not well researched. This study used a randomised trial to evaluate a seminar for general practice trainees on rational prescribing of antibiotics and benzodiazepines, two important areas of general practice prescribing. Results show a decrease in prescribing of antibiotics by the group of trainees attending the seminar but no effect on an already low level of benzodiazepine prescribing. The study provides evidence that group educational approaches to influencing prescribing behaviour can be effective.

Clinical competence of interns. Programme Evaluation Committee (PEC)

A clinical supervisors rating form addressing 13 competencies was used to assess the clinical competence of graduates one year after qualification in New South Wales (NSW), Australia. Data from 485 interns (97.2%) showed that graduates from the problem-based medical school were rated significantly better than their peers with respect to their interpersonal relationships, 'reliability' and 'self-directed learning'. Interns from one of the two traditional NSW medical schools had significantly higher ratings on 'teaching', 'diagnostic skills' and 'understanding of basic mechanisms'. Graduates from international medical schools performed worse than their peers on all competencies. These results were adjusted for age and gender. Additionally, women graduates and younger interns tended to have better ratings. Junior doctors have differing educational and other background experiences and their performance should be monitored.

Mental health care practices and educational needs of general practitioners

OBJECTIVES

To describe current mental health care practices of general practitioners and to identify their educational priorities and training preferences.

METHOD

Self-administered questionnaire to a stratified random sample of New South Wales general practitioners.

SUBJECTS

721 full-time general practitioners, of whom 534 (74%) responded.

RESULTS

Mental health problems recognised by general practitioners at least once per week were psychosomatic (93%), emotional (89%), addiction (79%), social/economic (71%) and family (69%). At least two-thirds recognised sexual problems, sexual abuse and major psychiatric problems less frequently than once per week. Sixty-four per cent of general practitioners reported that patients felt uncomfortable about being referred to psychiatrists; 53% that referral service waiting lists were too long; 51% that there were insufficient local mental health services; and 25% that communication difficulties between referring general practitioners and mental health specialists obstructed optimal care. Educational priorities were diagnostic and counselling skills, with particular emphasis on crisis, family, individual and marital counselling and strategies to prevent general practitioner burn-out.

CONCLUSIONS

General practitioners are interested in improving their mental health counselling and diagnostic skills but barriers remain. Both structural and educational initiatives are essential to enhance the quality of mental health care in general practice.

Antibiotic and benzodiazepine prescribing by general practice trainees

OBJECTIVE

To study the prescribing of antibiotics and benzodiazepines by a group of general practice trainees.

METHODS

Forty-six trainees in their general practice term with the Royal Australian College of General Practitioners Training Program and 495 experienced general practitioners were compared with regard to patients managed, prescribing of antibiotics for respiratory tract infections and prescribing of benzodiazepines for anxiety, sleep disorders and depression.

RESULTS

Trainees saw more young patients and patients with acute respiratory infections, and fewer patients with psychological problems, than the experienced practitioners. Trainees prescribed antibiotics less often for undifferentiated upper respiratory tract infection and their prescribing for tonsillitis was more frequently in agreement with prescribing guidelines. Trainees were less likely to prescribe a benzodiazepine for anxiety or sleep problems.

CONCLUSIONS

General practice trainees were relatively conservative prescribers of antibiotics and benzodiazepines. At times both groups did not prescribe in accordance with antibiotic prescribing guidelines and an appreciable number of patients continue to be prescribed benzodiazepines on a long term basis.

Interns' performances with simulated patients at the beginning and the end of the intern year

OBJECTIVE

To determine whether interns' performances of technical, preventive, and communication aspects of patient care improve during the intern year.

DESIGN

A descriptive study. At the beginning and end of the intern year, interns' consultations with three simulated (standardized) patients were videotaped and scored according to explicit criteria set by an expert panel. Problems simulated were urinary tract infection, bronchitis, and tension headache.

SETTING

The casualty outpatient department in a general teaching hospital in New South Wales, Australia.

PARTICIPANTS

Twenty-eight interns rotated to the casualty department.

RESULTS

Little improvement over the intern year in technical competence or preventive care was observed, even though initial levels of compliance with criteria were quite low for some items. Greater improvement was apparent in the area of communication skills.

CONCLUSIONS

The results suggest that the internship should be restructured to more adequately teach the skills required for primary care.

The effects of gender on diagnosis of psychological disturbance

This research examines the effect of patient gender on the detection of psychological disturbance. In Study 1, primary-care patients were requested to complete the General Health Questionnaire (GHQ), a measure of nonpsychiatric psychological disturbance, prior to their consultation. The patient's GHQ score was compared with physician judgments about the level of disturbance in that patient (N = 1913). Although there were a similar number of GHQ high scorers among males and females, the physicians classified significantly more females than males as disturbed. The doctors classified as disturbed a larger proportion of nondisturbed women than nondisturbed men. In order to explore the behavior of recent medical graduates, Study 2 examined the detection behavior of interns in an outpatient department with 384 of their patients. The interns behaved in a similar manner to the primary-care physicians.

Group C streptococcal bacteremia: analysis of 88 cases

Eighty-eight cases of group C streptococcal bacteremia were reviewed retrospectively. Most patients had underlying diseases (72.7%), predominantly cardiovascular disease (20.5%) or malignancy (20.5%). The infection originated most often from the upper respiratory tract (20.5%), the gastrointestinal tract (18.2%), or the skin (17.1%). Prior exposure to animals or animal products was reported in 23.9% of cases. The most common clinical manifestations of group C streptococcal bacteremia were endocarditis (27.3%), primary bacteremia (22.7%), and meningitis (10.2%). Of streptococcal isolates, 61.4% were not speciated, 19.3% were Streptococcus equisimilis, 17.1% were Streptococcus zooepidemicus, and two (2.3%) were Streptococcus equi. The isolates were sensitive to most antibiotics, and most patients were treated with beta-lactam agents. Mortality was high (25.0%), especially among older patients and patients with endocarditis, meningitis, and disseminated infection. Group C streptococcal bacteremia does not differ from bloodstream infection caused by other beta-hemolytic streptococci with regard to clinical presentation, treatment, or outcome.

Evaluating interns' performance using simulated patients in a casualty department

An observational study examined the care that was provided by 61 interns for three simulated (standardized) patients in a casualty department within a large teaching hospital. The consultations were recorded on videotape and were scored by reference to explicit criteria that were set by an expert panel. The criteria described standards of clinical competence, communication skills and preventive care for each of the three cases. An additional list of the general opportunities for preventive advice that were suggested by the patients' case histories also was compared with the interns' actual behaviour. Clinical competence was not demonstrated uniformly across the three cases. The problem of urinary-tract infection was managed best; 19% of the interns complied with all criteria, and 93% of the interns complied with 75% of the criteria. For tension headache, only 3% of the interns complied with all the criteria but 67% of interns complied with 75% of the criteria. In the case of bronchitis, only 3% of interns complied with all the criteria but 58% of interns met 75% of the criteria. The quality of preventive care also varied from case to case, being best for the patient with bronchitis and worst for the patient with tension headache. Over all, only three of the 13 criteria were met by more than half the interns. The communication-skills criteria identified three behaviours which the interns were most likely to omit: the interns summarized the patients' problems in only 73 of the 173 consultations; they explained the aetiology of the problems in only 127 of the 173 consultations; and they ensured that the patients understood their plan of management in only 21 of the 173 consultations.

Interns' identification of patients' health risks in a casualty department

This study examined whether the interns who staffed a hospital casualty department identified correctly four common health risks among their patients. When compared with patients who were attending general practitioners, patients who attended the casualty department were more likely to be cigarette smokers. They were also more likely to be heavy drinkers of alcohol and to score highly on a standardized measure of psychological disturbance. Women were less likely to have undergone a Papanicolaou smear-examination within the previous two years. The interns, who were the subjects in this study, failed to identify 56% of the smokers, 84% of the heavy drinkers, 35% of the psychologically-disturbed patients and 95% of the women who had not undergone a Papanicolaou smear-test in the last two years. The findings were in contrast with the interns' own opinions on what would constitute good-quality care in this setting. The subjects were just beginning their internship at the time of the study. Their failure to integrate important questions about common health risks suggests that their undergraduate training has been deficient in this area. The internship is the last formal opportunity to correct this deficiency before these doctors are registered for independent medical practice.

Response bias in a study of general practice

Response bias in quality of care research is an important, but largely neglected concern. Differences between health care professionals who consent to participate in research and those who do not may distort the conclusions and prevent the results being generalizable. This is particularly likely when response rates are low, as they often are in studies evaluating primary health care. The present study outlines a method for examining this important area. Fifty-six general practitioners who consented to participate in an observational study of general practice were compared with 52 doctors who declined to participate in the research. Comparisons were made of general characteristics including age, sex, practice size and postgraduate qualifications, as well as attitudes toward their role. This last analysis was deemed particularly important, as the attitudes expressed may have affected the behaviour of the doctor in the consultation, and therefore outcomes such as accurate diagnosis, compliance and satisfaction. Such outcomes are often the object of study in quality of care research. The only significant difference to emerge in the present study was that non-consenters were more strongly in favour of a medical system based on free enterprise and fee for service (t83 = 2.3P less than 0.05). No systematic differences were found on other general characteristics or attitudes relating to patient care. Response bias using the stated variables was therefore considered to be minimal. The results are discussed in terms of strategies aimed at increasing response rates in quality of care research.

Meningitis due to Staphylococcus aureus

A retrospective analysis of 10 adult patients with community-acquired Staphylococcus aureus meningitis was performed in order to elucidate the characteristics and treatment of this lethal disease. In all patients, a focus of infection outside the central nervous system was apparent at presentation. A poor prognosis was associated with severe underlying disease, greater degree of hyponatremia at presentation, development of seizures, failure of nuchal rigidity to develop, persistent or recurrent bacteremia, and the presence of concurrent S. aureus bronchopneumonia. Degree of deterioration in mental status and cerebrospinal fluid pleocytosis, protein levels, and glucose levels did not appear to have any prognostic significance. Therapy with rifampin and a semisynthetic penicillin effected a cure in all six patients treated with this regimen. In contrast, three of four patients treated with other antibiotic combinations died. On the basis of this experience, it is concluded that further trials with rifampin in combination with another anti-staphylococcal antibiotic for the treatment of S. aureus meningitis are warranted.