Validation study of machine-learning chest radiograph software in primary and emergency medicine.

AIM: To evaluate the performance of a machine learning based algorithm tool for chest radiographs (CXRs), applied to a consecutive cohort of historical clinical cases, in comparison to expert chest radiologists. MATERIALS AND METHODS: The study comprised 1,960 consecutive CXR from primary care referrals and the emergency department (992 and 968 cases respectively), obtained in 2015 at a UK hospital. Two chest radiologists, each with >20 years of experience independently read all studies in consensus to serve as a reference standard. A chest artificial intelligence (AI) algorithm, Lunit INSIGHT CXR, was run on the CXRs, and results were correlated with those by the expert readers. The area under the receiver operating characteristic curve (AUROC) was calculated for the normal and 10 common findings: atelectasis, fibrosis, calcification, consolidation, lung nodules, cardiomegaly, mediastinal widening, pleural effusion, pneumothorax, and pneumoperitoneum. RESULTS: The ground truth annotation identified 398 primary care and 578 emergency department datasets containing pathologies. The AI algorithm showed AUROC of 0.881-0.999 in the emergency department dataset and 0.881-0.998 in the primary care dataset. The AUROC for each of the findings between the primary care and emergency department datasets did not differ, except for pleural effusion (0.954 versus 0.988, p<0.001). CONCLUSIONS: The AI algorithm can accurately and consistently differentiate normal from major thoracic abnormalities in both acute and non-acute settings, and can serve as a triage tool.

Coronary artery calcification is associated with mortality independent of pulmonary embolism severity: a retrospective cohort study.

AIM: To assess coronary artery calcification (CAC) and vascular calcification in patients with pulmonary embolism (PE) and correlate this with mortality. MATERIALS AND METHODS: PE severity was quantified using computed tomography pulmonary angiography (CTPA) in 400 consecutive cases using the modified Miller score (1-5, mild; 6-11, moderate; 12-16, severe). Right ventricle strain was assessed using the right/left ventricle diameter (RV/LV) ratio. CAC score (CACS) was assessed using a four-point scale (CACS mild 1-3, moderate 4-8, severe 9-12) for each vessel and summed to give the total CACS. Follow-up for mortality was obtained at 3 years. RESULTS: PE severity was classified as mild in 48%, moderate in 21%, and severe in 32% of cases. The median modified Miller score was 6 (Interquartile range [IQR] 2, 14) and median total CACS was 2 (IQR 0, 7). All-cause mortality occurred in 128 (32%) patients. Patients with CAC were three times more likely to die than patients without CAC (Hazard ratio [HR] 2.96; 95% CI 1.84, 4.77; p<0.001), and patients with severe CAC were at the highest risk (HR 4.62; 95% CI 2.73, 7.83, p<0.001). Gender, modified Miller score and RV/LV ratio were not predictive of mortality. In multivariate analysis both CACS and age were independent predictors of 3-year all-cause mortality. Of the patients with CAC who died, the presence of coronary artery disease was only documented in 34 (32%). CONCLUSION: CACS is an independent predictor of all-cause mortality in patients with PE, and has important implications for subsequent patient management.

Positron Emission Tomography and Magnetic Resonance Imaging of Cellular Inflammation in Patients with Abdominal Aortic Aneurysms.

OBJECTIVES: Inflammation is critical in the pathogenesis of abdominal aortic aneurysm (AAA) disease. Combined (18)F-fludeoxyglucose ((18)F-FDG) positron emission tomography with computed tomography (PET-CT) and ultrasmall superparamagnetic particles of iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) are non-invasive methods of assessing tissue inflammation. The aim of this study was to compare these techniques in patients with AAA. MATERIALS AND METHODS: Fifteen patients with asymptomatic AAA with diameter 46 ± 7 mm underwent PET-CT with (18)F-FDG, and T2*-weighted MRI before and 24 hours after administration of USPIO. The PET-CT and MRI data were then co-registered. Standardised uptake values (SUVs) were calculated to measure (18)F-FDG activity, and USPIO uptake was determined using the change in R2*. Comparisons between the techniques were made using a quadrant analysis and a voxel-by-voxel evaluation. RESULTS: When all areas of the aneurysm were evaluated, there was a modest correlation between the SUV on PET-CT and the change in R2* on USPIO-enhanced MRI (n = 70,345 voxels; r = .30; p < .0001). Although regions of increased (18)F-FDG and USPIO uptake co-localised on occasion, this was infrequent (kappa statistic 0.074; 95% CI 0.026-0.122). (18)F-FDG activity was commonly focused in the shoulder region whereas USPIO uptake was more apparent in the main body of the aneurysm. Maximum SUV was lower in patients with mural USPIO uptake. CONCLUSIONS: Both (18)F-FDG PET-CT and USPIO-MRI uptake identify vascular inflammation associated with AAA. Although they demonstrate a modest correlation, there are distinct differences in the pattern and distribution of uptake, suggesting a differential detection of macrophage glycolytic and phagocytic activity respectively.

Long-term adverse effects associated with isolated below-knee deep-vein thrombosis: a 10-year follow-up study.

AIM: To assess the effect of the presence and locality of symptomatic lower-limb deep vein thrombosis (DVT) on mortality and morbidity following contrast venography (CV), the reference standard for diagnosing below-knee DVT, with a view to determining the prevalence of recurrent episodes of DVT and post-thrombotic syndrome (PTS). MATERIALS AND METHODS: Patients with clinical DVT undergoing investigation using CV were prospectively recorded. By retrospective case note examination and mortality data evaluation, 347 patients with DVT were matched with negative controls for mortality follow-up. Long-term complications were recorded. RESULTS: Fifty-one (14.7%) of the DVT patients were diagnosed with PTS and 43 (12.4%) with possible PTS in the 10 years following presentation. The relative risk for developing definite PTS was 0.544 for below- versus above-knee DVT; 9.9% with below-knee DVT had PTS, and 9% had probable PTS. Recurrent DVT occurred in 23.3% of patients with proximal DVT as opposed to 12.6% of patients with isolated below-knee DVT. CONCLUSIONS: Morbidity is greater in patients with proximal DVT; however, a significant, albeit smaller, proportion of patients with isolated below-knee DVT develop recurrent DVT and PTS. Below-knee DVT carries sufficient morbidity and mortality to warrant vigilance in diagnosis and management of this condition.

Ten years of imaging for pulmonary embolism: too many scans or the tip of an iceberg?

AIM: To examine the number and nature of investigations performed for suspected pulmonary embolism (PE) in a large teaching hospital and the change in incidence and severity of PE over a decade. MATERIALS AND METHODS: In this retrospective study, all patients investigated for suspected PE using computed tomography pulmonary angiography (CTPA) or lung scintigraphy during 10 years to March 2012 were identified and their records reviewed. In the final year, all reportedly positive CTPA cases were reviewed and PE severity calculated, for comparison with similar historical data. RESULTS: From 2002 to 2012, total annual investigations for suspected acute PE increased by 163% (805 to 2121). CTPA increased by 325% (475 to 2019). Detection of PE increased by 121% (193 to 426 per annum), with stable distribution of severity scores. The positive scan rate decreased from 24% to 20%. The mean age of patients being investigated for PE increased from 56 to 63 years. CONCLUSIONS: Increased detection of PE is not due to disproportionate increase in small PEs, but to increased detection of PE of all severities. This finding supports the hypothesis that PE is more common in the general population than previously appreciated, which may represent an iceberg phenomenon of previously undetected disease.

Imaging of cardiovascular risk in patients with Turner's syndrome.

Turner's syndrome is a disorder defined by an absent or structurally abnormal second X chromosome and affects around 1 in 2000 newborn females. The standardised mortality ratio in Turner's syndrome is around three-times higher than in the general female population, mainly as a result of cardiovascular disorders. Most striking is the early age at which Turner's syndrome patients develop the life-threatening complications of cardiovascular disorders compared to the general population. The cardiovascular risk stratification in Turner's syndrome is challenging and imaging is not systematically used. The aim of this article is to review cardiovascular risks in this group of patients and discuss a systematic imaging approach for early identification of cardiovascular disorders in these patients.

Feasibility of radiation dose reduction using AIDR-3D in dynamic pulmonary CT perfusion.

AIM: To assess the feasibility of radiation dose reduction with adaptive iterative dose reduction (AIDR-6 3D) reconstruction in dynamic pulmonary CT perfusion. MATERIALS AND METHODS: CTP examinations of 10 patients acquired at 100 kVp/50 mAs were reconstructed with filtered back projection (FBP) and AIDR-3D. Artificial noise was added to raw data (pre-reconstruction projection data) to simulate lower tube current scanning. Radiodensity (in Hounsfield units), noise, and perfusion values were compared. RESULTS: There was no significant difference in noise between the full and simulated reduced tube current with AIDR-3D reconstruction (p = 1). There was significantly lower noise in lung tissue with AIDR-3D images when compared to reconstructions without AIDR-3D (p = 0.005) and no significant change in the radiodensity (p = 1; mean difference <6 HU). Mean perfusion values increased significantly at lower tube currents (25 and 12.5 mAs), compared to 50 mAs (p = 0.005). This effect was significantly greater in larger patients compared to thin patients. CONCLUSION: AIDR-3D produced significantly lower noise images than FBP-based algorithms and maintained consistent noise levels in lung at 12.5 mAs, indicating this algorithm is suitable for reduced dose lung perfusion imaging. Iterative reconstruction allows significant radiation dose reduction of up to fourfold in smaller patients, and up to twofold in the medium/large size patients. The increase in perfusion values at 25% simulated tube currents is attributed to attenuation bias.

Aortic stenosis, atherosclerosis, and skeletal bone: is there a common link with calcification and inflammation?

AIMS: The pathophysiology of aortic stenosis shares many similarities with atherosclerosis and skeletal bone formation. Using non-invasive imaging, we compared aortic valve calcification and inflammation activity with that measured in atherosclerosis and bone. METHODS AND RESULTS: Positron emission and computed tomography was performed using 18F-sodium fluoride (18F-NaF, calcification) and 18F-fluorodeoxyglucose (18F-FDG, inflammation) in 101 patients with calcific aortic valve disease (81 aortic stenosis and 20 aortic sclerosis). Calcium scores and positron emission tomography tracer activity (tissue-to-background ratio; TBR) were measured in the aortic valve, coronary arteries, thoracic aorta, and bone. Over 90% of the cohort had coexistent calcific atheroma, yet correlations between calcium scores were weak or absent (valve vs. aorta r(2) = 0.015, P = 0.222; valve vs. coronaries r(2) = 0.039, P = 0.049) as were associations between calcium scores and bone mineral density (BMD vs. valve r(2) = 0.000, P = 0.766; vs. aorta r(2) = 0.052, P = 0.025; vs. coronaries r(2) = 0.016, P = 0.210). 18F-NaF activity in the valve was 28% higher than in the aorta (TBR: 2.66 ± 0.84 vs. 2.11 ± 0.31, respectively, P < 0.001) and correlated more strongly with the severity of aortic stenosis (r(2) = 0.419, P < 0.001) than 18F-NaF activity outwith the valve (valve vs. aorta r(2) = 0.167, P < 0.001; valve vs. coronary arteries r(2) = 0.174, P < 0.001; valve vs. bone r(2) = 0.001, P = 0.806). In contrast, 18F-FDG activity was lower in the aortic valve than the aortic atheroma (TBR: 1.56 ± 0.21 vs. 1.81 ± 0.24, respectively, P < 0.001) and more closely associated with uptake outwith the valve (valve vs. aorta r(2) = 0.327, P < 0.001). CONCLUSION: In patients with aortic stenosis, disease activity appears to be determined by local calcific processes within the valve that are distinct from atherosclerosis and skeletal bone metabolism.

Iterative reconstruction and individualized automatic tube current selection reduce radiation dose while maintaining image quality in 320-multidetector computed tomography coronary angiography.

AIM: To assess the effect of two iterative reconstruction algorithms (AIDR and AIDR3D) and individualized automatic tube current selection on radiation dose and image quality in computed tomography coronary angiography (CTCA). MATERIALS AND METHODS: In a single-centre cohort study, 942 patients underwent electrocardiogram-gated CTCA using a 320-multidetector CT system. Images from group 1 (n = 228) were reconstructed with a filtered back projection algorithm (Quantum Denoising Software, QDS+). Iterative reconstruction was used for group 2 (AIDR, n = 379) and group 3 (AIDR3D, n = 335). Tube current was selected based on body mass index (BMI) for groups 1 and 2, and selected automatically based on scout image attenuation for group 3. Subjective image quality was graded on a four-point scale (1 = excellent, 4 = non-diagnostic). RESULTS: There were no differences in age (p = 0.975), body mass index (p = 0.435), or heart rate (p = 0.746) between the groups. Image quality improved with iterative reconstruction and automatic tube current selection [1.3 (95% confidence intervals (CI): 1.2-1.4), 1.2 (1.1-1.2) and 1.1 (1-1.2) respectively; p < 0.001] and radiation dose decreased [274 (260-290), 242 (230-253) and 168 (156-180) mGy cm, respectively; p < 0.001]. CONCLUSION: The application of the latest iterative reconstruction algorithm and individualized automatic tube current selection can substantially reduce radiation dose whilst improving image quality in CTCA.

Hyperpolarised 3He MRI versus HRCT in COPD and normal volunteers: PHIL trial.

The aim of the present study was to apply hyperpolarised (HP) (3)He magnetic resonance imaging (MRI) to identify patients with chronic obstructive pulmonary disease (COPD) and alpha(1)-antitrypsin deficiency (alpha(1)-ATD) from healthy volunteers and compare HP (3)He MRI findings with high-resolution computed tomography (HRCT) in a multicentre study. Quantitative measurements of HP (3)He MRI (apparent diffusion coefficient (ADC)) and HRCT (mean lung density (MLD)) were correlated with pulmonary function tests. A prospective three centre study enrolled 122 subjects with COPD (either acquired or genetic) and age-matched never-smokers. All diagnostic studies were completed in 94 subjects (52 with COPD; 13 with alpha(1)-ATD; 29 healthy subjects; 63 males; and 31 females; median age 62 yrs). The consensus assessment of radiologists, blinded for other test results, estimated nonventilated lung volume (HP (3)He MRI) and percentage diseased lung (HRCT). Quantitative evaluation of all data for each centre consisted of ADC (HP (3)He MRI) and MLD measurements (HRCT), and correlation with forced expiratory volume in 1 s (FEV(1))/forced vital capacity (FVC) indicating airway obstruction, and the diffusing capacity of the lung for carbon monoxide (D(L,CO)) indicating alveolar destruction. Using lung function tests as a reference, regional analysis of HP (3)He MRI and HRCT correctly categorised normal volunteers in 100% and 97%, COPD in 42% and 69% and alpha(1)-ATD in 69% and 85% of cases, respectively. Direct comparison of HP (3)He MRI and CT revealed 23% of subjects with moderate/severe structural abnormalities had only mild ventilation defects. In comparison with lung function tests, ADC was more effective in separating COPD patients from healthy subjects than MLD (p<0.001 versus 0.038). ADC measurements showed better correlation with D(L,CO) than MLD (r = 0.59 versus 0.29). Hyperpolarised (3)He MRI correctly categorised patients with COPD and normal volunteers. It offers additional functional information, without the use of ionising radiation whereas HRCT gives better morphological information. We showed the feasibility of a multicentre study using different magnetic resonance systems.

PET scan in clinically suspected paraneoplastic neurological syndromes: a 6-year prospective study in a regional neuroscience unit.

BACKGROUND: The role of PET in the diagnosis of paraneoplastic neurological syndromes (PNS) has previously been reported in retrospective studies, from specialized neuro-oncology units, often selecting patients with positive paraneoplastic antibodies. OBJECTIVES: To prospectively assess the usefulness of PET in detecting malignancy in patients clinically suspected of having PNS. METHODS: PET was performed in patients suspected of PNS within 4 weeks of the normal CT body scan. All patients were followed up. RESULTS: Eighty patients suspected of having PNS underwent PET. 18/80 (23%) were abnormal and suspicious of malignancy. The total number of definite and probable PNS with abnormal PET was 11/18 (61%). The total number of definite and probable PNS with a normal PET was 3/62 (5%). Only 50% of patients with biopsy-proven malignancy were positive for paraneoplastic antibodies. The prevalence of abnormal PET in patients presenting with classical PNS was 41% as opposed to 21% in patients with non-classical PNS. The sensitivity and specificity of PET in diagnosing PNS was 75% and 87% respectively. CONCLUSIONS: PET is a valuable tool in clinically suspected PNS. Its use should not be restricted to specialized neuro-oncology units or in patients with positive paraneoplastic antibodies. Positive yield is the highest amongst patients with classical PNS.

Multimodality quantitative assessments of myocardial perfusion using dynamic contrast enhanced magnetic resonance and 15O-labelled water positron emission tomography imaging.

Kinetic modelling of myocardial perfusion imaging data allows the absolute quantification of myocardial blood flow (MBF) and can improve the diagnosis and clinical assessment of coronary artery disease (CAD). Positron emission tomography (PET) imaging is considered the reference standard technique for absolute quantification, whilst oxygen-15 (15O)-water has been extensively implemented for MBF quantification. Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) has also been used for MBF quantification and showed comparable diagnostic performance against (15O)-water PET studies. We investigated for the first time the diagnostic performance of two different PET MBF analysis softwares PMOD and Carimas, for obstructive CAD detection against invasive clinical standard methods in 20 patients with known or suspected CAD. Fermi and distributed parameter modelling-derived MBF quantification from DCE-MRI was also compared against (15O)-water PET, in a subgroup of 6 patients. The sensitivity and specificity for PMOD was significantly superior for obstructive CAD detection in both per vessel (0.83, 0.90) and per patient (0.86, 0.75) analysis, against Carimas (0.75, 0.65), (0.81, 0.70), respectively. We showed strong, significant correlations between MR and PET MBF quantifications (r=0.83-0.92). However, DP and PMOD analysis demonstrated comparable and higher haemodynamic differences between obstructive versus (no, minor or non)-obstructive CAD, against Fermi and Carimas analysis. Our MR method assessments against the optimum PET reference standard technique for perfusion analysis showed promising results in per segment level and can support further multi-modality assessments in larger patient cohorts. Further MR against PET assessments may help to determine their comparative diagnostic performance for obstructive CAD detection.

Efficacy and safety of gadodiamide (Gd-DTPA-BMA) in renal 3D-magnetic resonance angiography (MRA): a phase II study.

PURPOSE: To determine the most efficacious dose of gadodiamide for three-dimensional (3D) contrast-enhanced (CE) magnetic resonance angiography (MRA) of the renal arteries on a patient level based on the sensitivity in detecting the main hemodynamically relevant (> or =50% or occlusion) renal artery stenosis (RAS) using intra-arterial digital subtraction angiography (IA DSA) as the gold standard. MATERIALS AND METHODS: This prospective, randomized, double-blind, parallel-group, multicenter study included 273 patients referred to IA DSA for suspected RAS. Patients underwent 3D CE MRA after injection of 0.01, 0.05, 0.1, or 0.2mmol/kg of body weight gadodiamide (0.5mmol/ml). The images were assessed for location and degree of RAS by independent blinded readers (MRA: three readers, IA DSA: one reader). Hypothesis testing for a significant trend in sensitivity across dose groups was based on the one-sided Cochran-Armitage style trend test for each independent MRA reader. RESULTS: The lowest dose group (0.01mmol/kg) proved non-efficacious in detecting hemodynamically relevant (i.e., > or =50% or occlusion) RAS. A statistically significant dose trend (p<0.001) was shown for each of the three independent readers. Depending on reader, the sensitivity obtained with 0.05, 0.1, and 0.2mmol/kg was 63.9-86.1%, 75.8-91.4% and 80.6-90.6%, the specificity was 66.7-73.9%, 59.3-75.0%, and 59.3-75.0% and accuracy was 67.8-78.9%, 75.4-77.4%, and 76.3-81.0%, for the three dose groups, respectively. There were eight non-severe adverse events (AEs). Three serious AEs occurring in one patient were judged not related to gadodiamide by the on-site investigator. CONCLUSION: A significant dose trend between the four doses examined was observed. The lowest dose (0.01mmol/kg) differed significantly from those of the other three doses. Based on the analysis of the primary and secondary endpoints, 0.1mmol/kg gadodiamide appears to be the most suitable dose in diagnosing hemodynamically relevant RAS. The present study also demonstrated gadodiamide to be safe and well tolerated.

Cost-effectiveness analysis of various strategies in the diagnostic management of pulmonary embolism.

BACKGROUND: Since the clinical diagnosis of pulmonary embolism is unreliable, various objective diagnostic methods (or combinations thereof) are advocated. Pulmonary angiography is the accepted reference method but is considered less suitable for initial screening due to its invasive nature. Therefore, at least nine different diagnostic management strategies employing invasive and noninvasive diagnostic tests are used in clinical practice. We assessed the cost-effectiveness of these strategies to help identify the optimal approach. METHODS: Based on assumptions derived from published data, we calculated mortality, morbidity, adequacy for the indication of anticoagulant therapy, and associated diagnostic and therapeutic costs using a decision analytic model. Additionally, a cost-effectiveness analysis was performed using incremental costs per additional life saved. RESULTS: The analysis identified three separate categories of diagnostic management strategies: (1) Treatment of all patients (or of those with an abnormal perfusion scan) results in the lowest mortality and morbidity rates but the highest costs due to inappropriate treatment of 55% to 70% of patients. (2) Pulmonary angiography strategies with or without prior perfusion-ventilation lung scintigraphy and ultrasonography of the legs have comparable low mortality and morbidity rates, costs savings of approximately 40%, and inappropriate treatment in fewer than 5% of patients. (3) Use of perfusion-ventilation scintigraphy with or without ultrasonography results in unacceptably high mortality rates. CONCLUSIONS: At present, the optimal diagnostic management strategy should include pulmonary angiography. Use of perfusion-ventilation lung scintigraphy and ultrasonography results in a 40% to 50% reduction in the number of patients requiring pulmonary angiography and is cost-effective.

The clinical course of patients with suspected pulmonary embolism.

BACKGROUND: The outcome of patients with suspected pulmonary embolism is known to a limited extent only. OBJECTIVE: To address this limited knowledge in a cohort in whom pulmonary embolism was proved or ruled out. METHODS: Consecutive patients with clinically suspected pulmonary embolism underwent lung scintigraphy and angiography if required. Pulmonary embolism was excluded by normal results of a lung scan or angiogram, and, if so, anticoagulant therapy was withheld. Pulmonary embolism was proved with a high-probability perfusion-ventilation lung scan or a confirmatory angiogram if a nondiagnostic lung scan was obtained. These patients were treated with heparin intravenously and anticoagulants orally on a long-term basis. All patients were followed up for 6 months, with a special focus on recurrent thromboembolism, bleeding complications, and mortality. RESULTS: A total of 487 consecutive inpatients and outpatients were included. Pulmonary embolism was excluded or proved in 243 and 193 patients, respectively. In 51 patients a definite diagnosis could not be established. The overall prevalence of pulmonary embolism was 39%. In patients in whom pulmonary embolism was proved, excluded, or uncertain, recurrent venous thromboembolism was observed in 2.6%, 0.9%, and 2%, respectively. Serious bleeding complications occurred in 7 patients (3.3%; 95% confidence interval [CI], 1.8%-6.3%), 2 cases of which were fatal. The total mortality after 6 months in patients with proved or excluded pulmonary embolism was 17% (95% CI, 12%-23%) and 11% (95% CI, 7%-15%), respectively. Death was related to (recurrent) pulmonary embolism in 5% and 0% of these cases, respectively. CONCLUSIONS: During a 6-month period, recurrent pulmonary embolism occurred in approximately 5 patients (2.5%) who were treated for a previous episode. Fatal bleeding complications attributable to the use of anticoagulants were encountered in 1%. The mortality among patients with suspected pulmonary embolism was considerable. However, most deaths were unrelated to pulmonary embolism, but were the result of serious underlying illnesses.

'Presenting CXR phenotype of H1N1' flu compared with contemporaneous non-H1N1, community acquired pneumonia, during pandemic and post-pandemic outbreaks'.

AIMS: To review, phenotype and assess potential prognostic value of initial chest X-ray findings in patients with H1N1 influenza during seasonal outbreaks of 2009 and 2010, in comparison with non-H1N1, community acquired pneumonia (CAP). METHODS: We retrospectively identified 72 patients admitted to hospital with pneumonia during the seasons of 2009 and 2010. H1N1 cases were confirmed by virology PCR. Presenting chest X-rays were jointly read by 2 radiologists, who were 'blinded' to further patient details and divided into 6 zones. Total number of opacified zones, the pattern and distribution of changes and length of hospital stay were recorded. RESULTS: Patients with H1N1 demonstrated more opacified zones (mean of 2.9 compared with 2.0; p=0.006), which were bilateral in two-thirds compared with a quarter of those with non-H1N1 CAP (p=0.001). H1N1 radiographs were more likely to be 'patchy' versus 'confluent' changes of non-H1N1 CAP (p=0.03) and more often demonstrated peripheral distribution (p=0.01). H1N1 patients tended to stay in hospital longer (not significant; p=0.08). A positive correlation existed between number of affected zones and length of inpatient stay, which was statistically significant for the cohorts combined (p=0.02). The findings were the same for the two evaluated seasons. CONCLUSION: H1N1 patients demonstrated more extensive disease, which was more likely bilateral, 'patchy', and peripheral in distribution. With increasing global cases of H1N1, knowledge of the typical findings of the H1N1 presenting chest X-ray may assist with early triage of patients, particularly where rapid viral testing is not available.

Choosing a strategy for the diagnostic management of suspected scaphoid fracture: a cost-effectiveness analysis.

UNLABELLED: To assess the cost-effectiveness of various strategies for the diagnostic management of clinically suspected scaphoid fracture, a decision-analytic model was built to evaluate three strategies and to compare them with a (clairvoyant) reference diagnostic management strategy. METHODS: Evaluated strategies were: (A) repeated radiography up to 2 wk; (B) repeat radiography up to 6 wk; and (C) radiography, followed by bone scintigraphy in patients with negative initial radiographs. Therapy consisted of 12 wk of immobilization for a radiographically or scintigraphically proven fracture. Diagnostic costs, therapeutic costs, period of immobilization and nonunion rate were calculated for all three strategies. Estimates were derived from a descriptive management study using bone scintigraphy and available literature. Sensitivity analyses were performed. RESULTS: Overall costs were 273.7, 317.7 and 316.1 European Currency Units (ECU) for Strategies A, B and C, respectively (1 ECU = 1.15 U.S. dollar). Strategy B led to the longest average period of immobilization (8.6 wk), while Strategy A resulted in the highest nonunion rate (4.7%). The costs per nonunion saved for the additional use of bone scintigraphy (Strategy C) was ECU 2618 when compared to Strategy A. CONCLUSION: The use of bone scintigraphy in the diagnostic management of scaphoid fractures is accurate, convenient for patients and cost-effective.

Observer and biological variation of a rapid whole blood D-dimer test.

In consecutive patients with suspected venous thromboembolism the interobserver variability of the SimpliRED D-dimer test was evaluated by two observers who independently scored one plate, the between assay variation was performed simultaneously by a third independent observer, who assessed a second plate. The biological variation was studied, 1-4 hours later by an independent evaluation. A total of 155 patients entered the study, venous thromboembolism was present in 42 patients (28%). The interobserver variability was 2/83 samples, with a kappa of 0.95 (95% confidence interval 0.88-1.0). The between assay variation was 2/98, with a kappa value of 0.96 (95% confidence interval 0.90-1.0). When testing the biological variation the observers disagreed in 2 of 69 patients (3%). The SimpliRED D-dimer assay has a good to excellent interobserver variability, between assay variation and reproducibility.

Reliable rapid blood test for the exclusion of venous thromboembolism in symptomatic outpatients.

UNLABELLED: In this study we assessed the reliability of a rapid bed-side whole blood D-dimer assay prospectively in patients with clinically suspected venous thromboembolism, referred to the Academic Medical Centre, Amsterdam. In consecutive outpatients with clinically suspected deep vein thrombosis or pulmonary embolism we measured the sensitivity, specificity and negative predictive value of the assay compared to the outcome of standard diagnostic tests and 3-month follow-up. A total of 234 patients were included; the prevalence of venous thromboembolism was 29%. A sensitivity, specificity and negative predictive value of 100% (95% CI: 95% - 100%), 58% (95% CI: 50%-65%) and 100% (95% CI:96% - 100%), respectively, were obtained. The exclusion rate was 41% of all referred patients. CONCLUSION: The SimpliRED whole blood D-dimer assay appears to be a simple and reliable method for the exclusion of venous thromboembolism in symptomatic outpatients.

Rapid ELISA assay for plasma D-dimer in the diagnosis of segmental and subsegmental pulmonary embolism. A comparison with pulmonary angiography.

STUDY OBJECTIVE: To assess the accuracy of a rapid ELISA D-dimer assay for the exclusion of pulmonary embolism (PE) in patients suspected of PE, using pulmonary angiography alone as reference method rather than a diagnostic strategy including lung scintigraphy and leg vein ultrasonography. METHODS: In 342 patients who were examined by pulmonary angiography to diagnose or exclude PE, the accuracy of the quantitative rapid VIDAS D-dimer test for the exclusion of PE was evaluated retrospectively. D-dimer levels were assayed in frozen samples collected during the diagnostic work-up at the time of pulmonary angiography while on treatment with unfractionated heparin for 1-2 days. RESULTS: Mean plasma D-dimer concentrations were increased in patients with angiographic evidence of PE (P <0.0001). The sensitivity of D-dimer for segmental PE was 98%, its accuracy in excluding segmental PE was 99%, higher than the respective figures for subsegmental PE (76% and 94%; P <0.01, both). For both forms of PE combined the sensitivity was 90% and the negative predictive value 94%. DISCUSSION: The sensitivity and negative predictive values reported here, are low compared with previous studies using the same rapid ELISA D-dimer assay. This probably reflects an overlooking of mild cases of subsegmental PE in previous studies, although a reduction of D-dimer levels by the heparin pretreatment may have contributed to part of the discrepancy. Prospective studies are needed to clarify this issue.