On the choice of acceptance radius in free-response observer performance studies

OBJECTIVES

Choosing an acceptance radius or proximity criterion is necessary to analyse free-response receiver operating characteristic (FROC) observer performance data. This is currently subjective, with little guidance in the literature about what is an appropriate acceptance radius. We evaluated varying acceptance radii in a nodule detection task in chest radiography and suggest guidelines for determining an acceptance radius.

METHODS

80 chest radiographs were chosen, half of which contained nodules. We determined each nodule's centre. 21 radiologists read the images. We created acceptance radii bins of <5 pixels, <10 pixels, <20 pixels and onwards up to <200 and 200+ pixels. We counted lesion localisations in each bin and visually compared marks with the borders of nodules.

RESULTS

Most reader marks were tightly clustered around nodule centres, with tighter clustering for smaller than for larger nodules. At least 70% of readers' marks were placed within <10 pixels for small nodules, <20 pixels for medium nodules and <30 pixels for large nodules. Of 72 inspected marks that were less than 50 pixels from the centre of a nodule, only 1 fell outside the border of a nodule.

CONCLUSION

The acceptance radius should be based on the larger nodule sizes. For our data, an acceptance radius of 50 pixels would have captured all but 2 reader marks within the borders of a nodule, while excluding only 1 true-positive mark. The choice of an acceptance radius for FROC analysis of observer performance studies should be based on the size of larger abnormalities.

Quantifying the clinical relevance of a laboratory observer performance paradigm

OBJECTIVE

Laboratory observer performance measurements, receiver operating characteristic (ROC) and free-response ROC (FROC) differ from actual clinical interpretations in several respects, which could compromise their clinical relevance. The objective of this study was to develop a method for quantifying the clinical relevance of a laboratory paradigm and apply it to compare the ROC and FROC paradigms in a nodule detection task.

METHODS

The original prospective interpretations of 80 digital chest radiographs were classified by the truth panel as correct (C=1) or incorrect (C=0), depending on correlation with additional imaging, and the average of C was interpreted as the clinical figure of merit. FROC data were acquired for 21 radiologists and ROC data were inferred using the highest ratings. The areas under the ROC and alternative FROC curves were used as laboratory figures of merit. Bootstrap analysis was conducted to estimate conventional agreement measures between laboratory and clinical figures of merit. Also computed was a pseudovalue-based image-level correctness measure of the laboratory interpretations, whose association with C as measured by the area (rAUC) under an appropriately defined relevance ROC curve, is as a measure of the clinical relevance of a laboratory paradigm.

RESULTS

Low correlations (e.g. κ=0.244) and near chance level rAUC values (e.g. 0.598), attributable to differences between the clinical and laboratory paradigms, were observed. The absolute width of the confidence interval was 0.38 for the interparadigm differences of the conventional measures and 0.14 for the difference of the rAUCs.

CONCLUSION

The rAUC measure was consistent with the traditional measures but was more sensitive to the differences in clinical relevance. A new relevance ROC method for quantifying the clinical relevance of a laboratory paradigm is proposed.

Rodent models of pulmonary hypertension: harmonisation with the world health organisation's categorisation of human PH

The WHO classification of pulmonary hypertension (PH) recognises five distinct groups, all sharing a mean, resting, pulmonary artery pressure (PAP) > 25 mmHg. The aetiology of PH varies by group (1-pulmonary vascular disease, 2-high left heart filling pressures, 3-hypoxia, 4-unresolved pulmonary embolism and 5-miscellaneous). Inclusion in a group reflects shared histological, haemodynamic and pathophysiological features and has therapeutic implications. Advantages of using rodent models to understand the pathophysiology of human PH and to test experimental therapies include the economy, safety and mechanistic certainty they provide. As rodent models are meant to reflect human PH, they should be categorised by a parallel PH classification and limitations in achieving this ideal recognised. Challenges with rodent models include: accurate phenotypic characterisation (haemodynamics, histology and imaging), species and strain variations in the natural history of PH, and poor fidelity to the relevant human PH group. Rat models of group 1 PH include: monocrotaline (± pneumonectomy), chronic hypoxia + SU-5416 (a VEGF receptor inhibitor) and the fawn-hooded rat (FHR). Mouse models of group 1 PH include: transgenic mice overexpressing the serotonin transporter or dominant-negative mutants of bone morphogenetic protein receptor-2. Group 1 PH is also created by infecting S100A4/Mts1 mice with γ-herpesvirus. The histological features of group 1 PH, but not PH itself, are induced by exposure to Schistosoma mansoni or Stachybotrys chartarum. Group 3 PH is modelled by exposure of rats or mice to chronic hypoxia. Rodent models of groups 2, 4 and 5 PH are needed. Comprehensive haemodynamic, histological and molecular phenotyping, coupled with categorisation into WHO PH groups, enhances the utility of rodent models.

The relationship between coping and subclinical psychotic experiences in adolescents from the general population--a longitudinal study

BACKGROUND

Subclinical psychotic experiences during adolescence may represent liability for developing psychotic disorder. Both coping style and the degree of persistence of psychotic experiences may play a role in the progression to clinical psychotic disorder, but little is known about the causal relationship between the two.

METHOD

Path modelling was used to examine longitudinal relationships between subclinical positive psychotic experiences and three styles of coping (task-, emotion- and avoidance-oriented) in an adolescent general population sample (n=813) assessed three times in 3 years. Distinct developmental trajectories of psychotic experiences, identified with growth mixture modelling, were compared on the use of these coping styles.

RESULTS

Over time, emotion-oriented coping in general was bi-directionally related to psychotic experiences. No meaningful results were found for task- or avoidance-oriented coping. Females reported using a wider range of coping styles than males, but the paths between coping and psychotic experiences did not differ by gender. Persistence of psychotic experiences was associated with a greater use of emotion-oriented coping, whereas a decrease in experiences over time was associated with an increased use of task-orientated coping.

CONCLUSIONS

Emotion-oriented coping is the most important coping style in relation to psychotic experiences, as it may contribute to a 'vicious cycle' and is associated with persistence of experiences. In addition, more task-oriented coping may result in a decrease in psychotic experiences. Results suggest that opportunities for intervention may already be present at the level of subclinical psychosis.

Impact of troponin 1 on long-term mortality after emergency orthopaedic surgery in older patients

OBJECTIVES

To determine the association between post-operative troponin rises and longer term (2-year) mortality after emergency orthopaedic surgery in patients over 60 years of age.

METHODS

One hundred and two patients were recruited in 2006 and had inpatient troponin 1 measurements. These patients were followed up by a telephone call annually for complications.

RESULTS

At 2 years, 29.4% (30/102) of patients had died. Twenty-five patients (25/54 or 49.3%) with a troponin rise were dead at 2 years compared with five patients without a troponin rise (5/48 or 10.4%), which was significantly different P < 0.0001. Patients with a higher troponin level (>0.1 µg/L) were more likely to be dead at 2 years compared with those with a lower level of troponin. However, when adjusted for other comorbidities the association between troponin elevation and death at 2 years did not persist. Using Cox regression multivariate analysis, only one factor, sustaining an in-hospital cardiac event odds ratio 4.3 (95% confidence interval 1.8-10.3, P = 0.001), was associated with 2 years all-cause mortality . Furthermore, patients who sustained a symptomatic troponin rise (P < 0.0001) or asymptomatic troponin rise (P = 0.004) were more likely to have died at 2 years compared with those with no troponin rise. Three factors were significantly associated with a cardiac event during the second year: (i) post-operative troponin rise (P = 0.05); (ii) pre-morbid atrial fibrillation (P = 0.04); and (iii) post-operative renal failure (P < 0.001).

CONCLUSION

Elevated post-operative troponin levels are predictive of 1-year but not 2-year mortality in older patients undergoing emergency orthopaedic surgery.

Randomised controlled trial of thermostatic mixer valves in reducing bath hot tap water temperature in families with young children in social housing

OBJECTIVES

To assess the effectiveness of thermostatic mixing valves (TMVs) in reducing bath hot tap water temperature, assess acceptability of TMVs to families and impact on bath time safety practices.

DESIGN

Pragmatic parallel arm randomised controlled trial.

SETTING

A social housing organisation in Glasgow, Scotland, UK.

PARTICIPANTS

124 families with at least one child under 5 years.

INTERVENTION

A TMV fitted by a qualified plumber and educational leaflets before and at the time of TMV fitting.

MAIN OUTCOME MEASURES

Bath hot tap water temperature at 3-month and 12-month post-intervention or randomisation, acceptability, problems with TMVs and bath time safety practices.

RESULTS

Intervention arm families had a significantly lower bath hot water temperature at 3-month and 12-month follow-up than families in the control arm (3 months: intervention arm median 45.0°C, control arm median 56.0°C, difference between medians, -11.0, 95% CI -14.3 to -7.7); 12 months: intervention arm median 46.0°C, control arm median 55.0°C, difference between medians -9.0, 95% CI -11.8 to -6.2) They were significantly more likely to be happy or very happy with their bath hot water temperature (RR 1.43, 95% CI 1.05 to 1.93), significantly less likely to report the temperature as being too hot (RR 0.33, 95% CI 0.16 to 0.68) and significantly less likely to report checking the temperature of every bath (RR 0.84, 95% CI 0.73 to 0.97). Seven (15%) intervention arm families reported problems with their TMV.

CONCLUSIONS

TMVs and accompanying educational leaflets are effective at reducing bath hot tap water temperatures in the short and longer term and are acceptable to families. Housing providers should consider fitting TMVs in their properties and legislators should consider mandating their use in refurbishments as well as in new builds.

G-protein beta3 subunit polymorphism and bleeding in the orbofiban in patients with unstable coronary syndromes-thrombolysis in myocardial infarction 16 trial

SUMMARY BACKGROUND

Variability in platelet response to antiplatelet drugs is heritable. A common single base substitution (825C>T) in the G-protein beta polypeptide 3 (GNB3) gene leads to alternative splicing (41-amino-acid deletion) of the human G-protein beta3 (Gbeta3) subunit. This truncated protein carried by GNB3 T allele carriers is linked to coronary artery disease and implicated as a genetic marker of drug response. Large studies of Caucasians associate T allele carriage with lower platelet reactivity.

OBJECTIVES

To evaluate whether the GNB3 genotype would predispose to bleeding in patients treated with a GPIIb/IIIa receptor antagonist.

METHODS

GNB3 genotype distribution was determined in DNA samples from patients in the orbofiban in patients with unstable coronary syndromes-thrombolysis in myocardial infarction (OPUS-TIMI) 16 genetic sub-study. Impact of genotype on the bleeding endpoint and the composite primary endpoint of death, myocardial infarction (MI), re-hospitalization for ischemia and urgent revascularization was estimated in the treatment and placebo arm.

RESULTS

Out of 887 patients, 45.1% carried the GNB3 CC genotype, 44.5% CT and 10.4% TT. Interaction between T allele carriership and treatment for bleeding was significant (P = 0.008). This reflects the fact that GNB3 non-T carriers treated with orbofiban had no bleeding effect compared with placebo (RR = 0.92, 95% CI 0.55-1.55) whereas T carriers did (RR = 2.62, 95% CI 1.58-4.35, P < 0.001). Interaction between T allele carriership and treatment was not significant for the primary endpoint (P = 0.18) or MI (P = 0.69).

CONCLUSION

The GNB3 T allele significantly increased bleeding in patients treated with the platelet antagonist orbofiban. Our findings suggest that risk of bleeding associated with an antiplatelet agent is heritable and may be dissociated from risk of thrombosis.

A heavy heart; A massive right atrial myxoma causing fatigue and shortness of breath

Cardiac myxomas are rare. The clinical diagnosis of an atrial myxoma may occur in an asymptomatic patient but may also present with cardiac failure, syncope, arrythmias, or with vascular evidence of tumour embolisation. The delay in diagnosis from presentation is approximately ten months. We present the case of a 53-year-old woman who attended our Emergency Department with dyspnoea, fatigue and left sided chest pain. Investigations revealed a massive right atrial myxoma. The tumour was resected successfully. Emergency Physicians should be aware of the subtle ways in which an atrial myxoma can present because of the potential for fatal outcomes.

Procedural discourse in intellectual disability and dual diagnosis

BACKGROUND

Knowledge of discourse abilities of adults with intellectual disability (ID) and mental illness is limited. The present study examined the procedural discourse skills of two cohorts of adults with ID - one cohort with (n = 7) and one cohort without (n = 7) a psychiatric diagnosis of psychosis.

METHODS

Participants completed the 'dice game', a procedural discourse elicitation procedure that has been used by previous researchers.

RESULTS

Results revealed that while all participants demonstrated an understanding of the task, participants with ID alone were more able to communicate the key elements of the game than the participants in the dual diagnosis group.

CONCLUSIONS

Results of this investigation suggest that individuals with dual diagnosis have difficulties that may relate to previously identified discourse impairments in people with schizophrenia, and this may relate to a larger difficulty in taking into account the listener's needs.

Characteristics of hormone therapy, cognitive function, and dementia: the prospective 3C Study

OBJECTIVES

To examine the association between hormone therapy (HT) and cognitive performance or dementia, focusing on the duration and type of treatment used, as well as the timing of initiation of HT in relation to the menopause.

METHODS

Women 65 years and older were recruited in France as part of the Three City Study. At baseline and 2- and 4-year follow-up, women were administered a short cognitive test battery and a clinical diagnosis of dementia was made. Detailed information was also gathered relating to current and past HT use. Analysis was adjusted for a number of sociodemographic, behavioral, physical, and mental health variables, as well as APOE epsilon4.

RESULTS

Among 3,130 naturally postmenopausal women, current HT users performed significantly better than never users on verbal fluency, working memory, and psychomotor speed. These associations varied according to the type of treatment and a longer duration of HT appeared to be more beneficial. However, initiation of HT close to the menopause was not associated with better cognition. HT did not significantly reduce dementia risk over 4 years but current treatment diminished the negative effect associated with APOE epsilon4.

CONCLUSIONS

Current hormone therapy (HT) was associated with better performance in certain cognitive domains but these associations are dependent on the duration and type of treatment used. We found no evidence that HT needs to be initiated close to the menopause to have a beneficial effect on cognitive function in later life. Current HT may decrease the risk of dementia associated with the APOE epsilon4 allele.