Patient preferences in coronary revascularization

BACKGROUND

This study was performed to assess patient preferences for consequences of 3 coronary revascularization procedures: angioplasty, conventional coronary bypass surgery, and minimally invasive coronary bypass surgery.

METHOD

A nationwide sample of 3 types of respondents was recruited: respondents with no heart disease (n = 89), respondents with heart disease who had not undergone cardiac surgery (n = 97), and respondents with heart disease who had undergone cardiac surgery (n = 118).

RESULTS

Sixty-two percent ranked the risk of repeat revascularization as the most important concern, followed by postprocedure pain (22%), time to recovery of physical functioning (8%), time in hospital (4%), and body appearance (4%). Respondents preferred angioplasty to conventional and minimally invasive cardiac surgery if the 3-year risk of repeat revascularization with angioplasty were to decline to less than 28% and 21%, respectively.

CONCLUSION

These data suggest that patient preference should influence individual and policy recommendations when choosing among coronary revascularization procedures.

Tissue oxygen distribution in head and neck cancer patients

BACKGROUND

The importance of hypoxia in limiting the sensitivity of tumor cells to ionizing radiation has long been known.

METHODS

We evaluated the tissue oxygenation status with a polarographic needle electrode system in 37 patients with malignancies of the head and neck and correlated the pO2 of 25 patients with treatment outcome.

RESULTS

Sixteen tumors contained areas of severe hypoxia, defined by pO2 values below 2.5 mm Hg. Tumor oxygenation parameters were not correlated with hemoglobin, age, and history of tobacco use. There were no subcutaneous PO2 values below 10 mm Hg (ie, no areas of moderate or severe hypoxia), whereas this degree of hypoxia was commonly found in the tumors. Though not statistically significant, hypoxic tumors showed trends for poorer treatment outcome.

CONCLUSION

Our data demonstrate a great interindividual variability in the oxygenation of head and neck cancers and appears unassociated with clinical parameters. The method is capable of identifying patients with poorly oxygenated tumors, thereby providing important information for selecting patients who might need customized therapy designed to kill hypoxic tumor cells. Hypoxic tumors show a consistent trend for poor treatment outcome.

An intervention to increase patients' trust in their physicians. Stanford Trust Study Physician Group

PURPOSE

To investigate the effect of a one-day workshop in which physicians were taught trust-building behaviors on their patients' levels of trust and on outcomes of care.

METHOD

In 1994, the study recruited 20 community-based family physicians and enrolled 412 consecutive adult patients from those physicians' practices. Ten of the physicians (the intervention group) were randomly assigned to receive a one-day training course in building and maintaining patients' trust. Outcomes were patients' trust in their physicians, patients' and physicians' satisfaction with the office visit, continuity in the patient-physician relationship, patients' adherence to their treatment plans, and the numbers of diagnostic tests and referrals.

RESULTS

Physicians and patients in the intervention and control groups were similar in demographic and other data. There was no significant difference in any outcome. Although their overall ratings were not statistically significantly different, the patients of physicians in the intervention group reported more positive physician behaviors than did the patients of physicians in the control group.

CONCLUSIONS

The trust-building workshop had no measurable effect on patients' trust or on outcomes hypothesized to be related to trust.

Catheter ablation of accessory pathways, atrioventricular nodal reentrant tachycardia, and the atrioventricular junction: final results of a prospective, multicenter clinical trial. The Atakr Multicenter Investigators Group

BACKGROUND

The purpose of this study was to evaluate the safety and efficacy of a temperature-controlled radiofrequency catheter ablation system.

METHODS AND RESULTS

The patient population included 1050 patients who had undergone ablation of atrioventricular nodal reentrant tachycardia (AVNRT), an accessory pathway (AP), or the atrioventricular junction (AVJ). Ablation was successful in 996 patients. The probability of success was highest among patients who had undergone ablation of the AVJ, lowest in patients who had undergone ablation of an AP, and in between for patients who had undergone ablation of AVNRT. A major complication occurred in 32 patients. Four variables predicted ablation success (AVJ, AVNRT, or left free wall AP ablation and an experienced center). Four factors predicted arrhythmia recurrence (right free wall, posteroseptal, septal, and multiple APs). Two variables predicted development of a complication (structural heart disease and the presence of multiple targets), and 3 variables predicted an increased risk of death (heart disease, lower ejection fraction, and AVJ ablation).

CONCLUSIONS

These findings may serve as a guide to clinicians considering therapeutic options in patients who are candidates for ablation.

Pretreatment and midtreatment measurement of oxygen tension levels in head and neck cancers

OBJECTIVE

Considerable evidence exists to suggest that tumor hypoxia results in radioresistance. Historically, it has been difficult to assess tumor oxygen tension levels reliably. These levels can now be assessed in head and neck malignancies using the Eppendorf pO2 histograph, which uses a fine-needle electrode and a computerized micromanipulator. This technology was used to compare the pretreatment tumor oxygen tension level in lymph node metastases of patients with head and neck cancer to measurements taken during nonsurgical treatment after a partial response had been achieved.

STUDY DESIGN

Prospective study.

METHODS

Oxygen tension levels were measured in the cervical lymph nodes of 10 patients with biopsy-proven head and neck squamous cell carcinoma and cervical metastases who were being treated with nonsurgical management. These levels were obtained using the Eppendorf pO2 histograph system. Measurements were taken before the start of treatment and were repeated when the size of the cervical metastatic node had decreased by 50%. Normal subcutaneous tissue was measured during the same session. The mean and median pO2 levels, as well as the percentage of measurements with pO2 less than 5 mm Hg were determined.

RESULTS

A mean of 72.6 measurements per session was taken from each lymph node. The median tumor pO2 measurement fell from a mean (+/-SD) of 13.9+/-8.0 mm Hg to 7.3+/-9.9 mm Hg. Even more dramatic, however, was the substantial increase in the percentage of values less than 5 mm Hg, a rise from 29% to 52%.

CONCLUSIONS

While there is variability both in the pretreatment oxygenation of head and neck cervical metastases and in the change in tumor oxygen tension during treatment, there appears to be a decrease in the overall oxygenation of the tumors. The dramatic increase in very low oxygen measurements may reflect selective survival of radioresistant or chemoresistant hypoxic tumor cells. Cells at the very low level would be expected to be radiobiologically hypoxic (resistant to radiation-induced cell kill).

Donor blood monocytes but not T or B cells facilitate long-term allograft survival after total lymphoid irradiation

BACKGROUND

Previous studies showed that a combination of posttransplant total lymphoid irradiation (TLI), rabbit antithymocyte globulin (ATG), and a single donor blood transfusion induced tolerance to ACI heart allografts in Lewis rats. All three modalities were required to achieve tolerance. The objective of the current study was to determine the subset(s) of cells in the donor blood that facilitated long-term allograft survival.

METHODS

Lewis hosts received TLI, ATG, and donor cell infusion after heart transplantation. Graft survival, mixed leukocyte reaction (MLR), and intragraft cytokine mRNA were studied.

RESULTS

The intravenous injection of 25 x 10(6) ACI peripheral blood mononuclear cells (PBMC) significantly prolonged graft survival as compared with that of Lewis hosts given TLI and ATG alone. Injection of highly enriched blood T cells or splenic B cells adjusted for the number contained in 25 x 10(6) PBMC failed to induce significant graft prolongation. Unexpectedly, depletion of monocytes (CD11b+ cells) from PBMC resulted in the loss of graft prolongation activity. Enriched populations of monocytes obtained by plastic adherence were more efficient in prolonging graft survival than PBMC on a per cell basis. Hosts with long-term grafts (>100-day survival) showed evidence of immune deviation, because the MLR to ACI stimulator cells was vigorous, but secretion of interferon-gamma in the MLR was markedly reduced. In situ hybridization studies of long-term grafts showed markedly reduced levels of interferon-gamma mRNA as compared with rejecting grafts.

CONCLUSION

Infusion of donor monocytes facilitated graft prolongation via immune deviation.

Prediction of postoperative knee flexion in Insall-Burstein II total knee arthroplasty

Postoperative knee flexion in patients undergoing Insall-Burstein-II total knee arthroplasty at 2 years was evaluated regarding two basic questions: what groups of patients gain or lose the most flexion and what groups of patients have the best or worst postoperative flexion. Thirteen preoperative variables (maximum flexion, flexion arc, tibiofemoral angle, quadriceps strength, extensor lag, Knee Society score, Knee Society patient assessment, gender, age, height, weight, diagnosis, and surgeon) and four postoperative variable (leg length change, tibiofemoral angle, distance from patella to the joint line, and the tibial prosthesis anteroposterior translation on a lateral radiograph) were used in an attempt to explain postoperative flexion. The analysis was performed on 164 consecutive Insall-Burstein-II total knees in which the data were gathered prospectively on a time oriented medical record database. A regression tree analysis was used to identify several groups of patients, characterized by preoperative factor values, who had markedly above average performance on postoperative flexion. The preoperative factors identified include preoperative flexion, flexion arc, tibiofemoral angle, extensor lag, diagnosis, and age. The only postoperative variable of significance was tibiofemoral angle. Among the potential determinants of postoperative flexion that failed to appear predictive were the Knee Society scores and surgeon. Preoperative flexion is known to be a critical determinant of postoperative flexion in total knee replacement. However, in the current study, preoperative flexion accounted for only half of the difference between the best (122 degrees) and the worst (88 degrees) group, as determined with regression tree analysis.

Rheumatoid arthritis in the Pima Indians: the intersection of epidemiologic, demographic, and genealogic data

OBJECTIVE

To describe the clinical features and familial distribution of rheumatoid arthritis (RA) in the Pima Indians.

METHODS

From 1965 through 1990, all cases of RA as defined by the American College of Rheumatology (formerly, the American Rheumatism Association) 1987 criteria or all cases of seropositive, erosive disease as defined by the Rome criteria were identified in individuals who were age 20 years and older and were of 50% or more Pima/Tohono-O'odham heritage. Radiographs were reviewed by 2 musculoskeletal radiologists who were blinded to case status. Kinship coefficients were used to evaluate familial aggregation.

RESULTS

Eighty-eight RA cases were identified from this population-based sample. Over 66% of the cases had seropositive disease, over 60% had erosive disease, and over 40% had subcutaneous nodules. Of the 88 RA cases, 40 were members of families with more than 1 RA case. The remainder were simplex cases.

CONCLUSION

In this population, clinical markers of severe RA were present in a majority of cases. The presence of familial aggregation for RA in the Pima Indians suggests underlying genetic factors in disease pathogenesis.

A simple method of sample size calculation for linear and logistic regression

A sample size calculation for logistic regression involves complicated formulae. This paper suggests use of sample size formulae for comparing means or for comparing proportions in order to calculate the required sample size for a simple logistic regression model. One can then adjust the required sample size for a multiple logistic regression model by a variance inflation factor. This method requires no assumption of low response probability in the logistic model as in a previous publication. One can similarly calculate the sample size for linear regression models. This paper also compares the accuracy of some existing sample-size software for logistic regression with computer power simulations. An example illustrates the methods.

Postural balance measurements for children and adolescents

Measurements of standing balance were determined for 92 children and adolescents, 5-18 years old, while they stood on a force plate with eyes open or eyes closed. The measurements included center-of-pressure calculations for path length per second, average radial displacement, anterior-posterior and mediolateral amplitudes, area per second, mean frequency of sway, Brownian random motion measure of short-term diffusion coefficient, and long-term scaling exponent. All balance parameters improved from youngest to oldest subjects, and the parameters improved when measured with the subjects' eyes open compared with closed. The mean values for data from three trials varied by only 5% when compared with the mean values from 10 trials. Data from this study suggest that force-plate center-of-pressure data can be used to determine differences in standing balance between children and adolescents of different ages and those with movement and balance abnormalities.

Recursive partitioning for the identification of disease risk subgroups: a case-control study of subarachnoid hemorrhage

Recursive partitioning is a nonparametric technique that produces a classification tree in which subjects are assigned to mutually exclusive subsets according to a set of predictor variables. We examined the utility of recursive partitioning as a supplement to logistic regression for the multivariable analysis of data from case-control studies, demonstrating the technique using data from women enrolled in a population-based study of subarachnoid hemorrhage. The classification tree produced by recursive partitioning consisted of three main risk subgroups: (1) elderly women who had long-standing hypertension and who were not smokers, (2) middle-aged women who were cigarette smokers and frequent binge drinkers, and (3) women in whom risk variables indicate relative estrogen deficiency (i.e., postmenopausal status, no recent exposure to hormone replacement therapy, cigarette smoking). As a supplemental method, recursive partitioning not only identifies subgroups with varying risks, but also may uncover interactions between variables that may be overlooked in the traditional application of logistic regression to case-control data.

The relationship of running to osteoarthritis of the knee and hip and bone mineral density of the lumbar spine: a 9 year longitudinal study

OBJECTIVE

To determine the associations between running and radiographic hip osteoarthritis (OA), the progression of radiographic knee OA, and changes in bone mineral density (BMD) after 9 year followup in 28 members of a running club now aged 60-77 years and 27 nonrunner controls.

METHODS

Running subjects and nonrunning controls were matched for age (+/- 2 years), years of education, and occupation. All subjects underwent rheumatologic examination, completed annual questionnaires, and had radiographs taken of the knees in 1984, 1986, 1989, and 1993 and of the hips in 1993. BMD of the first lumbar spine vertebrae was obtained in 36 subjects by quantitative computed tomography (QCT) in 1984, 1986, 1989, and 1993. In 1993, knee radiographs were assessed in pairs (1984 and 1993), and hip radiographs were scored by 2 readers individually without knowledge of running status.

RESULTS

Nine year radiographic results for both runners and nonrunners for the knees showed significant within-group progression of both osteophytes and total knee radiographic scores (p = 0.01 for runners and p = 0.05 for nonrunners) and joint space narrowing in nonrunners (p = 0.01). Runners tended to have higher radiographic scores, but no significant differences in between-group differences were seen in 1984 or 1993. Radiographic OA of the hip was not different between the groups. QCT of the first lumbar vertebrae for BMD in 1984, 1986, 1989, and 1993 was greater in runners than nonrunners (p = 0.01), but rates of change in QCT values were similar between the 2 groups (p < 0.001).

CONCLUSION

The presence of radiographic hip OA and the progression of radiographic knee OA was similar for older runners and nonrunners. Lumbar spine BMD remained higher in runners, but changes in lumbar BMD were similar for runners and nonrunners over a 9 year period.

Hip osteoarthritis prevalence estimates by three radiographic scoring systems

OBJECTIVE

To estimate and compare the age- and sex-specific prevalence of radiographic hip osteoarthritis (RHOA) in a population-based study of the Pima Indians, using 3 atlas-based methods for assessing features of RHOA.

METHODS

Pelvic radiographs from 755 Pima Indians age > or = 45 years enrolled in a population-based study were read using the Kellgren/Lawrence (K/L) grading scale (grade 0-4) and 2 validated individual-radiographic-features (IRF) scales (grades 0-3 for narrowing and osteophytes).

RESULTS

The age- and sex-specific prevalence of RHOA among Pima Indians assessed using the K/L scale was < 10% in all age and sex groups. The prevalence of grade > or = 2 osteophytes assessed using the 2 IRF scales were similar to each other in all age and sex groups. However, differences between the 2 IRF scoring systems were found for the prevalence of grade > or = 2 joint space narrowing.

CONCLUSION

Pima Indians have an age- and sex-specific prevalence of RHOA similar to that found in the US population. Our finding of different joint space narrowing prevalence by the 2 IRF grading scales supports the use of the same atlas-based case definitions for determining disease prevalence for comparative studies.

Temperature dependence of the electrogenic reaction in the QB site of the Rhodobacter sphaeroides photosynthetic reaction center: the QA-QB --> QAQB- transition

The temperature dependencies for the kinetics and relative amplitudes of electrogenic reaction(s) coupled with the first reduction of the secondary quinone acceptor QB were measured with dark-adapted chromatophores of Rhodobacter sphaeroides. The kinetics, while acceptably fitted by a single exponent at room temperature, clearly split into two components below 15 degrees C (rise times, 25 micros and 300 micros at pH 7.0 and 10 degrees C) with the slow phase ousting the fast one at pH > 9.0. The activation energies of the fast and slow phases were estimated at pH 7.0 as < 10 kJ/mol and 60-70 kJ/mol, respectively. To explain the kinetic heterogeneity of the QB --> QB- transition, we suggest two possible conformations for the neutral oxidized ubiquinone at the QB site: one with a hydrogen bond between the side chain carboxyl of Glu-L212 and the methoxy oxygen at C3 of the QB ring (QB-H-Glu centers) and the other one, without this bond (QB:Glu- centers). The fast phase is attributed to QA- QB-H-Glu --> QA QB-H-Glu transition, whereas the slow one to the QA- QB:Glu- --> QA- QB-H-Glu --> QA QB(-)-H-Glu transition.

Children's thinking in the wake of Challenger

OBJECTIVE

The Challenger spacecraft explosion in 1986 offered an opportunity to study the thinking of normal children after a sudden and distant disaster, differences in thinking among children of different levels of emotional concern and different ages, and changes in their thinking over time.

METHOD

The authors studied six thinking patterns known to characterize childhood posttraumatic stress disorder and four additional hypothesized patterns in 153 randomly selected children of Concord, N.H. (who watched the explosion on television) and Porterville, Calif. (who heard about it later). They compared the structured-interview responses of the more involved (East Coast) and less involved (West Coast) children, of the latency-age children and the adolescents, and of the children initially (5-7 weeks after the explosion) and 14 months later.

RESULTS

The children exhibited the 10 predictable thinking patterns. They initially defended themselves, denying the reality of the explosion. They later fantasized about it. They tried to cope by seeking additional information on their own, at home, and at school. Most children talked about Challenger, but a minority of the latency-age youngsters avoided related talk and thoughts. The adolescents experienced more paranormal thinking, philosophical changes, and negative attitudes. Over the year, omens, paranormal experiences, and Challenger-based fantasies tended to disappear, but negative views about institutions and the world's future held steady or increased.

CONCLUSIONS

The children's thinking followed predictable patterns. A higher degree of emotional involvement (East Coast children) was strongly linked to these thinking patterns, as was being an adolescent. Distant disasters appear to set up commonalities of thought that might come to characterize certain generations of children.

Identifying hospitalized older patients at varying risk for physical performance decline: a new approach

OBJECTIVE

A classification tree analysis identifies patient groups at varying risk for decline in physical performance 1 year after hospitalization.

DESIGN

Prospective cohort study.

SETTING

Tertiary care VAMC.

PARTICIPANTS

A total of 507 acutely ill hospitalized male veterans aged 65 years and older.

MEASUREMENTS

Eighteen admission characteristics were considered as potential predictors: demographic data, medical diagnoses, functional status (e.g., ADL and IADL), geriatric conditions (e.g., incontinence, vision impairment, weight change), mental status, depression, and physical functioning (measured by self-report (MOS-PFR) and the Physical Performance and Mobility Examination (PPME)). Outcome measure was change in PPME status at 12-months post-admission.

RESULTS

Patients with the greatest risk for decline had both high baseline physical performance (PPME > or = 9) and at least moderate self-report limitations on physical functioning (MOS-PFR < or = 36, mean = 30.8). Patients with the lowest risk of decline had impaired baseline physical performance (PPME < or = 8) but fewer self-report limitations on physical functioning (MOS-PFR > or = 31, mean = 37.4) and two or less geriatric conditions.

CONCLUSIONS

The predictive role of self-report functioning suggests that perception of the impact of health on one's own physical functioning is associated with future performance. The number of geriatric conditions is also an important predictor of physical performance change. By identifying patient risk groups based on geriatric conditions, physical performance, and self-report physical functioning, future targeting strategies may improve physical performance outcomes for hospitalized older adults.

Analysis of estrogen receptor messenger RNA in breast carcinomas from archival specimens is predictive of tumor biology

As the size of breast tumors continues to decrease, it has become more difficult to obtain adequate tumor tissue for molecular studies. We have used the estrogen receptor (ER) gene as a model to study the ability to perform a quantitative analysis of ER mRNA extracted from archival breast carcinoma specimens using reverse transcriptase polymerase chain reaction. Based upon ER mRNA abundance, tumors were characterized as having low, medium, or high ER mRNA expression. These data were compared with ER and progesterone receptor (PR) status determined by enzyme immunoassay, tumor histology, and Bloom-Richardson grade. Comparing the low and high ER mRNA groups, there were statistically significant differences in ER-positive status (10% versus 95%; P = 0.0001), PR-positive status (10% versus 90%; P = 0.0001), and tumor grade (2.67 +/- 0.12 versus 2.09 +/- 0.14; P = 0.0025). Of the 28 tumors in the high ER mRNA group, 5 (18%) were invasive lobular carcinomas whereas all 24 tumors with low ER mRNA were invasive ductal carcinomas. These data demonstrate that archival breast tumor specimens can be characterized for ER mRNA abundance. In addition, we conclude that the mechanisms regulating ER gene transcription influence the phenotype of breast carcinomas. These results also suggest that this technique can be designed to provide a quantitative analysis of gene expression for any gene of interest utilizing archival tumor specimens.

The relationship of clinical knowledge to months of clinical training among medical students

PURPOSE

To assess the correlation of the number of months of clinical training with clinical knowledge, as measured by the United States Medical Licensing Examination (USMLE) Step 2.

METHOD

The total number of months of clinical training and percentile scores on USMLE Step 2 were determined for 217 Stanford. University School of Medicine graduates from 1992 through 1994. Percentile scores on each subsection of the Medical College Admission Test (MCAT) and the National Board of Medical Examiners Part 1 or USMLE Step 1 (Part 1/Step 1) for the graduates were also determined. For some analyses the graduates were separated into three groups according to the duration of clinical training. The Pearson product-moment correlation coefficient was used to quantify and define the significance of correlations. The Jorickheere-Terpstra nonparametric test was used to assess trends across the three groups. A multiple linear regression model was used to test the effects of confounding variables.

RESULTS

The total numbers of clerkship months ranged from 12 to 23; the median was 18. A highly significant correlation was found between increasing months of clinical training and increasing scores on Step 2 (p = .002); a weaker significant correlation was found with scores on Part 1/Step 1 (p = .03). The correlation for Step 2 scores did not diminish appreciably (p = .004) when scores for Part 1/Step 1 and each MCAT subsection were introduced into the regression model.

CONCLUSION

A highly significant correlation was found between the amount of clinical training and the acquisition and utilization of clinical knowledge. In the current climate of concerns about the rising costs of medical education, the impulse to solve these concerns by decreasing the amount of medical students' clinical training should be approached with caution.

Comparing two diagnostic tests against the same "gold standard" in the same sample

Methods are proposed for comparing two diagnostic tests for the same data where a threshold for positive for each test is specified. One method contrasts the diagnostic tests' estimated risks. A second method compares the two tests' kappa coefficients. When thresholds for positive test results are specified a priori, maximum likelihood estimators and their asymptotic variances are derived and test statistics are presented for both case-control and naturalistic methods of sampling. The bootstrap is proposed as a method to assess differences in risk estimators when thresholds for positive test results are chosen by scanning the data. Examples are given to illustrate the methods.

6-Ketocholestanol is a recoupler for mitochondria, chromatophores and cytochrome oxidase proteoliposomes

The effect of 6-ketocholestanol (kCh) on various natural and reconstituted membrane systems has been studied. 6-ketocholestanol (5 alpha-Cholestan-3 beta-ol-6-one), a compound increasing the membrane dipole potential, completely prevents or reverses the uncoupling action of low concentrations of the most potent artificial protonophore SF6847. This effect can be shown in the rat liver and heart muscle mitochondria, in the intact lymphocytes, in the Rhodobacter sphaeroides chromatophores, and in proteoliposomes with the heart muscle or Rh. sphaeroides cytochrome oxidase. The recoupling effect of kCh disappears within a few minutes after the kCh addition and cannot be observed at all at high SF6847 concentrations. Almost complete recoupling is also shown with FCCP, CCCP, CCP and platanetin. With 2,4-dinitrophenol, fatty acids and gramicidin, kCh is ineffective. With TTFB, PCP, dicoumarol, and zearalenone, low kCh concentrations are ineffective, whereas its high concentrations recouple but partially. The kCh recoupling is more pronounced in mitochondria, lymphocytes and proteoliposomes than in chromatophores. On the other hand, mitochondria, lymphocytes and proteoliposomes are much more sensitive to SF6847 than chromatophores. A measurable lowering of the electric resistance of a planar bilayer phospholipid membrane (BLM) are shown to occur at SF6847 concentrations which are even higher than in chromatophores. In BLMs, kCh not only fails to reverse the effect of SF6847, but even enhances the conductivity increase caused by this uncoupler. It is assumed that action of low concentrations of the SF6847-like uncouplers on coupling membranes involves cytochrome oxidase and perhaps some other membrane protein(s) as well. This involvement is inhibited by the asymmetric increase in the membrane dipole potential, caused by incorporation of kCh to the outer leaflet of the membrane.

An index for assessing blindness in a multi-centre clinical trial: disulfiram for alcohol cessation--a VA cooperative study

This paper considers an index to assess the success of blinding with application to a clinical trial of disulfiram. The index increases as the success of blinding increases, accounts for uncertain responses, and is scaled to an interval of 0.0 to 1.0, 0.0 being complete lack of blinding and 1.0 being complete blinding.

Optimization of thoracic spiral CT: effects of iodinated contrast medium concentration

PURPOSE

To determine the effect of varying iodine concentration on arterial enhancement and perivenous artifact during thoracic spiral computed tomographic (CT) scanning.

MATERIALS AND METHODS

One hundred thirty-eight outpatients received 15.0 g (n = 76) or 22.5 g (n = 62) of iodine (300 mg/mL iodine) while undergoing thoracic spiral CT. Patients received either undiluted contrast medium, 1:1 normal saline dilution, or 3:1 normal saline dilution. Contrast medium was injected at a flow rate determined to deliver the entire iodine dose within 40 seconds. Attenuation was measured within arteries and veins. Three blinded thoracic radiologists independently graded perivenous artifact and arterial enhancement.

RESULTS

Perivenous artifacts were statistically significantly reduced with successive iodine dilution (P < .002). Arterial enhancement was statistically significantly better with 15.0 g of iodine diluted 1:1 when compared with the same iodine dose undiluted or diluted 3:1 (P < .01). Arterial enhancement achieved with 15.0 g of iodine diluted 1:1 was not statistically significantly lower than that achieved with 22.5 g of iodine diluted 1:1 (P > .31); however, venous artifact was greater with 22.5 g of iodine (P < .004).

CONCLUSION

Reduced iodine concentration appears to diminish perivenous artifact and to result in improved arterial enhancement during thoracic spiral CT.