Variability between laboratories performing coagulation tests with identical platforms: a nationwide evaluation study.

BACKGROUND While the assessment of analytical precision within medical laboratories has received much attention in scientific enquiry, the degree of as well as the sources causing variation between them remains incompletely understood. In this study, we quantified the variance components when performing coagulation tests with identical analytical platforms in different laboratories and computed intraclass correlations coefficients (ICC) for each coagulation test. METHODS Data from eight laboratories measuring fibrinogen twice in twenty healthy subjects with one out of 3 different platforms and single measurements of prothrombin time (PT), and coagulation factors II, V, VII, VIII, IX, X, XI and XIII were analysed. By platform, the variance components of (i) the subjects, (ii) the laboratory and the technician and (iii) the total variance were obtained for fibrinogen as well as (i) and (iii) for the remaining factors using ANOVA. RESULTS The variability for fibrinogen measurements within a laboratory ranged from 0.02 to 0.04, the variability between laboratories ranged from 0.006 to 0.097. The ICC for fibrinogen ranged from 0.37 to 0.66 and from 0.19 to 0.80 for PT between the platforms. For the remaining factors the ICC's ranged from 0.04 (FII) to 0.93 (FVIII). CONCLUSIONS Variance components that could be attributed to technicians or laboratory procedures were substantial, led to disappointingly low intraclass correlation coefficients for several factors and were pronounced for some of the platforms. Our findings call for sustained efforts to raise the level of standardization of structures and procedures involved in the quantification of coagulation factors.

MODIFICATION AND IMPLEMENTATION OF THE RPC HETEROGENEOUS THORAX PHANTOM FOR VERIFICATION OF PROTON THERAPY TREATMENT PROCEDURES

The Radiological Physics Center (RPC) provides heterogeneous phantoms that are used to evaluate radiation treatment procedures as part of a comprehensive quality assurance program for institutions participating in clinical trials. It was hypothesized that the existing RPC heterogeneous thorax phantom can be modified to assess lung tumor proton beam therapy procedures involving patient simulation, treatment planning, and treatment delivery, and could confirm agreement between the measured dose and calculated dose within 5%/3mm with a reproducibility of 5%. The Hounsfield Units (HU) for lung equivalent materials (balsa wood and cork) was measured using a CT scanner. The relative linear stopping power (RLSP) of these materials was measured. The linear energy transfer (LET) of Gafchromic EBT2 film was analyzed utilizing parallel and perpendicular orientations in a water tank and compared to ion chamber readings. Both parallel and perpendicular orientations displayed a quenching effect underperforming the ion chamber, with the parallel orientation showing an average 31 % difference and the perpendicular showing an average of 15% difference. Two treatment plans were created that delivered the prescribed dose to the target volume, while achieving low entrance doses. Both treatment plans were designed using smeared compensators and expanded apertures, as would be utilized for a patient in the clinic. Plan 1a contained two beams that were set to orthogonal angles and a zero degree couch kick. Plan 1b utilized two beams set to 10 and 80 degrees with a 15 degree couch kick. EBT2 film and TLD were inserted and the phantom was irradiated 3 times for each plan. Both plans passed the criteria for the TLD measurements where the TLD values were within 7% of the dose calculated by Eclipse. Utilizing the 5%/3mm criteria, the 3 trial average of overall pass rate was 71% for Plan 1a. The 3 trial average for the overall pass rate was 76% for Plan 1b. The trials were then analyzed using RPC conventional lung treatment guidelines set forth by the RTOG: 5%/5mm, and an overall pass rate of 85%. Utilizing these criteria, only Plan 1b passed for all 3 trials, with an average overall pass rate of 89%.

The Development and Implementation of an Anthropomorphic Head Phantom for the Assessment of Proton Therapy Treatment Procedures

Proton therapy has become an increasingly more common method of radiation therapy, with the dose sparing to distal tissue making it an appealing option, particularly for treatment of brain tumors. This study sought to develop a head phantom for the Radiological Physics Center (RPC), the first to be used for credentialing of institutions wishing to participate in clinical trials involving brain tumor treatment of proton therapy. It was hypothesized that a head phantom could be created for the evaluation of proton therapy treatment procedures (treatment simulation, planning, and delivery) to assure agreement between the measured dose and calculated dose within ±5%/3mm with a reproducibility of ±3%. The relative stopping power (RSP) and Hounsfield Units (HU) were measured for potential phantom materials and a human skull was cast in tissue-equivalent Alderson material (RLSP 1.00, HU 16) with anatomical airways and a cylindrical hole for imaging and dosimetry inserts drilled into the phantom material. Two treatment plans, proton passive scattering and proton spot scanning, were created. Thermoluminescent dosimeters (TLDs) and film were loaded into the phantom dosimetry insert. Each treatment plan was delivered three separate times. Each treatment plan passed our 5%/3mm criteria, with a reproducibility of ±3%. The hypothesis was accepted and the phantom was found to be suitable for remote audits of proton therapy treatment facilities.

The Forensic Reference Phantom-a new tool for quality assurance of attenuation measurements in forensic radiology

Introduction The purpose of this paper is to present the technical specifications of the Forensic Reference Phantom (FRP), to test its behavior relative to organic test materials, and discuss potential applications of the phantom in forensic radiology. Materials and method The FRP prototype is made of synthetic materials designed to simulate the computed tomography (CT) attenuation of water. It has six bore holes that accommodate multiuse containers. These containers were filled with test materials and scanned at 80 kVp, 120 kVp, and 140 kVp. X-ray attenuation was measured by two readers. Intra- and inter-reader reliability was assessed using the intra-class correlation coefficient (ICC). Significance levels between mean CT numbers at 80 kVp, 120 kVp, and 140 kVp were assessed with the Friedman-test. The T-test was used to assess significance levels between the FRP and water. Results Overall mean CT numbers ranged from −3.0–3.7HU for the FRP; −1000.3–−993.5HU for air; −157.7– −108.1HU for oil; 35.5–42.0HU for musle tissue; and 1301.5–2354.8HU for cortical bone. Inter-reader and intra-reader reliability were excellent (ICC>0.994; and ICC=0.999 respectively). CT numbers were significantly different at different energy levels. There was no significant difference between the attenuation of the FRP and water. Conclusions The FRP is a new tool for quality assurance and research in forensic radiology. The mean CT attenuation of the FRP is equivalent to water. The phantom can be scanned during routine post-mortem CT to assess the composition of unidentified objects. In addition, the FRP may be used to investigate new imaging algorithms and scan protocols in forensic radiology.

Orthodontic retention procedures in Switzerland.

OBJECTIVE To survey retention procedures used in orthodontic practices in Switzerland. MATERIAL AND METHODS A questionnaire previously developed by Renkema et al. (2009) was sent to 223 Swiss orthodontists. The questionnaire comprised six parts, mainly containing multiple-choice questions. Information as to background education of the individual orthodontist, retention in general, frequency of different types of removable or bonded retainers that were used, retention pro- tocol, and the type and size of the wire used for bonded retainers was assessed. RESULTS The overall response rate was 65 percent. Most orthodontists placed a bonded retainer in the upper and lower arch, except when the upper arch was expanded during treatment or when extractions were performed in the upper arch, in which case they placed a combination of fixed and removable retainers. Opinions varied with regard to how many hours the removable retainers should be worn and the duration of the retention phase. As far as bonded retainers were concerned, 87 percent of the orthodontists preferred life-long retention. Ninety-three percent of the orthodontists considered that the development of a guide- line on retention procedures would be useful. CONCLUSIONS The choice of retention procedures is mostly based on orthodontists personal preference. A further research into the long-term effectiveness of individual retention protocols is needed.

Technical complications and failures of zirconia-based prostheses supported by implants followed up to 7 years: a case series.

PURPOSE To evaluate technical complications and failures of zirconia-based fixed prostheses supported by implants. MATERIALS AND METHODS Consecutive patients received zirconia-based single crowns (SCs) and fixed dental prostheses (FDPs) on implants in a private clinical setting between 2005 and 2010. One dentist performed all surgical and prosthetic procedures, and one master technician performed and coordinated all laboratory procedures. One-piece computer-aided design/ computer-assisted manufacture technology was used to fabricate abutments and frameworks, which were directly connected at the implant level, where possible. All patients were involved in a recall maintenance program and were finally reviewed in 2012. Data on framework fractures, chipping of veneering ceramics, and other technical complications were recorded. The primary endpoint was failure of the prostheses, ie, the need for a complete remake. A life table analysis was calculated. RESULTS A total of 289 implants supported 193 zirconia-based prostheses (120 SCs and 73 FDPs) in 127 patients (51 men, 76 women; average age: 62.5 ± 13.4 years) who were reviewed in 2012. Twenty-five (13%) prostheses were cemented on 44 zirconia abutments and 168 (87%) prostheses were screw-retained directly at the implant level. Fracture of 3 frameworks (1 SC, 2 FDPs) was recorded, and significant chipping resulted in the remake of 3 prostheses (1 SC, 2 FDPs). The 7-year cumulative survival rate was 96.4% ± 1.99%. Minor complications comprised 5 loose screws (these were retightened), small chips associated with 3 prostheses (these were polished), and dislodgement of 3 prostheses (these were recemented). Overall, 176 prostheses remained free of technical problems. CONCLUSIONS Zirconia-based prostheses screwed directly to implants are clinically successful in the short and medium term.

Hospital trends of admissions and procedures for acute leg ischaemia in England, 2000-2011.

INTRODUCTION Acute leg ischaemia (ALI) is a common vascular emergency for which new minimally invasive treatment options were introduced in the 1990s. The aim of this study was to determine recent hospital trends for ALI in England and to assess whether the introduction of the new treatment modalities had affected management. METHODS Routine hospital data covering ALI were provided by Hospital Episode Statistics for the years 2000 to 2011 and mortality data were obtained from the Office for National Statistics. All data were age standardised, reported per 100,000 of the population, and stratified by age band (60-74 years and ≥75 years) and sex. RESULTS Hospital admissions have risen significantly from 60.3 to 94.3 per 100,000 of the population, with an average annual increase of 6.2% since 2003 (p<0.001). The rise was greater in the older age group (from 79.9 to 134.4 vs 49.3 to 73.0) and yet procedures for ALI have shown a significant decrease since 2000 from 14.3 to 12.4 per 100,000 (p=0.013), independent of age and sex. Open embolectomy of the femoral artery remains the most common procedure and the proportion of endovascular interventions showed only a small increase. Only a few deaths were attributed to ALI (range: 95-150 deaths per year). CONCLUSIONS Hospital workload for ALI has increased, particularly since 2003, but this trend does not appear to have translated into increased endovascular or surgical activity.

Aortic valve replacement and concomitant procedures with the Perceval valve: results of European trials.

BACKGROUND The Perceval (Sorin Group, Milan, Italy) is a self-anchoring sutureless aortic valve prosthesis. We report the short- to midterm results of combined aortic valve replacement (AVR) with concomitant procedures in elderly patients undergoing operation as part of 3 consecutive prospective multicenter European studies. METHODS From April 2007 to February 2013, 243 patients (mean age, 79.7 ± 5.1 years; female patients, 61%; median EuroSCORE, 9%) underwent AVR with concomitant procedures. The concomitant procedures were coronary artery bypass grafting (CABG) (182 cases), septal myectomy (21 cases), CABG + other procedures (18 cases), and 22 other procedures. Primary and secondary end points included implant feasibility and safety (for mortality and morbidity) and efficacy (New York Heart Association [NYHA] class improvement and hemodynamic results) of the prosthesis at the different follow-up periods. Data were expressed as mean ± standard deviation. Kaplan-Meier analysis was performed for survival analysis. RESULTS Mean aortic cross-clamp and extracorporeal circulation (ECC) times were 50.7 ± 22.8 minutes and 78.9 ± 32.3 minutes, respectively. Thirty-day mortality was 2.1%. Mean postoperative gradient and effective orifice area were 10.1 ± 4.7 mm Hg and 1.5 ± 0.4 cm(2) and 8.9 ± 5.6 mm Hg and 1.6 ± 0.4 cm(2), respectively, at 1 year. There were early explantations, 4 of which resulted from paravalvular leaks. One additional valve explantation resulted from aortic root bleeding, probably caused by excessively extensive decalcification. In the late period, there was 1 mild paravalvular leak and no intravalvular insufficiency. No migration, dislodgement, or degeneration of the valve occurred during follow-up. Median follow-up was 444 days. CONCLUSIONS These trials confirm the safety and efficacy of the Perceval sutureless aortic valve, especially in elderly patients requiring AVR + concomitant procedures. In this patient group, sutureless valves may be advantageous compared to transcatheter valve implantations as concomitant procedures other than percutaneous coronary artery angioplasty are not always possible in the latter.