The standard error of measurement is a more appropriate measure of quality for postgraduate medical assessments than is reliability: an analysis of MRCP(UK) examinations

Background  

Cronbach's alpha is widely used as the preferred index of reliability for medical postgraduate examinations. A value of 0.8-0.9 is seen by providers and regulators alike as an adequate demonstration of acceptable reliability for any assessment. Of the other statistical parameters, Standard Error of Measurement (SEM) is mainly seen as useful only in determining the accuracy of a pass mark. However the alpha coefficient depends both on SEM and on the ability range (standard deviation, SD) of candidates taking an exam. This study investigated the extent to which the necessarily narrower ability range in candidates taking the second of the three part MRCP(UK) diploma examinations, biases assessment of reliability and SEM.     

Triterpene trimers from Maytenus scutioides: cycloaddition compounds?

Two novel trimers, triscutins A and B (1 and 2), based on pristimerin triterpene units, were isolated and characterized from Maytenus scutioides. Their structures were determined on the basis of spectroscopic evidence, including 1H-13C heteronuclear correlation (HMQC), long-range correlation with inverse detection (HMBC), and ROESY NMR experiments; and their absolute configurations, by means of CD studies. Compounds 1 and 2 were assayed for antimicrobial and cytotoxic activities, and their possible biosynthetic route is proposed.     

Reference values for lead in blood in urban population in southern Brazil]

OBJECTIVE: To describe the reference values for lead in blood in an urban population in the city of Londrina, in the state of Paraná, Brazil. MATERIALS AND METHODS: The reference population was composed of 520 adult volunteers who were assessed from November 1994 to December 1996. Exclusion criteria were: occupational exposure to lead, exposure through personal habits or practices, smoking more than 10 cigarettes per day, and living near industrial plants or other places that use lead in their production processes. Also excluded were individuals with abnormal clinical or laboratory results or with chronic diseases or cardiovascular disorders. Lead blood levels were determined using air-acetylene flame atomic absorption spectrophotometry. The detectable limit was 1.23 micrograms/dL. After the analyses of lead in blood, the following values were determined: minimum value, first quartile, median, third quartile, and maximum value; geometric mean; 95% confidence interval; experimental interval; and reference value. RESULTS: The reference values for lead in blood ranged from 1.20 micrograms/dL to 13.72 micrograms/dL. The geometric mean was 5.5 micrograms/dL. CONCLUSIONS: In general, the values found in this study are lower than those that have been reported for other countries. Additional data should be gathered from Brazilian populations living in more-industrialized areas.     

Infectious keratitis: correlation between corneal and contact lens cultures.

PURPOSE: This article reports a study of the effectiveness of performing contact lens cultures to identify causative organisms of infectious keratitis in patients using extended-wear soft contact lenses (cosmetic or therapeutic). METHODS: Patients' records from the Ocular Microbiology Laboratory of the Department of Ophthalmology, Paulista School of Medicine, from 1976 to 2000, and data of patients with contact lens-related keratitis in which the contact lens had been cultured were collected and reviewed. RESULTS: One hundred thirteen patients were included. Only soft contact lenses had been cultured and 29.2% of them were therapeutic contact lenses. An overall concordance of 84.0% was found between cultures obtained from corneal scrapings and contact lenses, with a higher rate in fungal keratitis (100%) compared to amebic (80.0%) and bacterial (74.5%) keratitis. In cases of concomitant bacterial growth in cultures of scrapings and contact lenses, the same organism was detected in 97.04%. Most cases of bacterial infection were caused by Pseudomonas spp. Among the discordant cases (16%), a microorganism was more likely to be isolated by contact lens culture (94.4%). CONCLUSION: Contact lens cultures may identify the causative organisms in most cases of contact lens-related keratitis. The clinical relevance of positive contact lens cultures in keratitis with negative corneal cultures needs further investigation.     

A highly sensitive and specific chemiluminescent enzyme-linked immunosorbent assay for diagnosis of active Trypanosoma cruzi infection

BACKGROUND: Chagas' disease is transmitted to man either by the bite of insects harboring Trypanosoma cruzi or by the transfusion of blood from infected donors. The conventional serologic testing as presently used in blood banks in South America is unsatisfactory, because of a high number of inconclusive and false-positive results. Other methods such as polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA) with recombinant antigens have been proposed, but inherent difficulties have so far precluded their adoption in the large-scale screening required by blood banks. STUDY DESIGN AND METHODS: A highly sensitive and specific chemiluminescent ELISA using a purified trypomastigote glycoconjugate antigen and a complex epimastigote antigen was devised for the diagnosis of active T. cruzi infection. RESULTS: Chemiluminescent ELISA was 100-percent sensitive in the diagnosis of 100 cases of confirmed Chagas' disease. Inconclusive results and false-positive reactions were eliminated in a panel of 115 sera.The specificity of the chemiluminescent ELISA was 100 percent with a purified trypomastigote glycoconjugate antigen and 99.7 percent with a complex epimastigote antigen when applied to 1000 normal human sera and 288 heterologous sera from patients with other infections, including leishmaniasis, and vaccinated individuals. CONCLUSION: The chemiluminescent ELISAs provide a test that is highly sensitive (purified trypomastigote glycoconjugate and complex epimastigote antigens) and specific (purified trypomastigote glycoconjugate antigen) for Chagas' disease diagnosis. It can be used in blood bank screening and to monitor the treatment of patients undergoing chemotherapy.     

Comparison of Pulmonary Artery Pressure Measurements in the Supine and 60° Lateral Positions Leanne is continuing this research in her doctoral studies

Pulmonary artery pressure monitoring, with the patient in both the supine and lateral positions, is an essential element in the assessment of critically ill patients. Previous work offers conflicting results regarding the accuracy of measurements obtained with the patient in the lateral position. The purpose of this study was to determine if accurate pulmonary artery pressure measurements can be obtained in the cardiac surgical patient. Thirty-five patients underwent repositioning between the supine and both the left and right 60° lateral position while being mechanically ventilated and then breathing spontaneously. Pulmonary artery pressure measurements were recorded prior to, two minutes following and ten minutes following repositioning. Despite some variation in results the pulmonary capillary wedge pressure measurement was reliable ten minutes after repositioning in both the spontaneously breathing and mechanically ventilated patient. Other pulmonary artery pressure measurements were not so reliable in the lateral position. This study concludes that clinical practitioners can obtain accurate pulmonary capillary wedge pressure measurements in post-operative cardiac surgical patients positioned in either the left or right 60° lateral position. Further research is however required, with larger numbers from all sub-groups of the critical care population. Physiological and pathophysiological characteristics which preclude reliable pulmonary artery pressure measurements need to be identified.     

Electrical interference from an abdominal muscle stimulator unit on an implantable cardioverter defibrillator: report of two consecutive cases

Two consecutive cases are presented of patients with ICDs in whom the use of commercial units for muscle stimulation for abdominal training caused interference with the device, mimicked cardiac signals, and resulted in inappropriate treatment shock delivery.     

Trichinella infection and clinical disease

Trichinellosis is caused by ingestion of insufficiently cooked meat contaminated with infective larvae of <it>Trichinella</it> species. The clinical course is highly variable, ranging from no apparent infection to severe and even fatal disease. We report two illustrative cases of trichinellosis. Returning to Denmark a few days after having eaten roasted pork in the Republic of Serbia, a female patient suffered from severe vomiting, epigastric pain, diarrhoea, and later myalgia, generalized oedema, and prostration. A biopsy showed heavy infestation with <it>Trichinella spiralis</it>, 2000 larvae/g of muscle. Life-threatening cardiopulmonary, renal and central nervous system complications developed. The patient recovered after several months. Her husband, who also ate the pork, did not have clinical symptoms, but an increased eosinophil count and a single larva in a muscle biopsy confirmed infection. The epidemiology, clinical manifestations, diagnosis, treatment and prevention of trichinellosis are reviewed.