Dipyridamole is superior to dobutamine for thallium stress imaging: a randomised crossover study.

OBJECTIVE--To assess the value of dobutamine over dipyridamole as a pharmacological stressing agent in myocardial perfusion imaging with thallium-201. DESIGN--Stress and redistribution tomographic images were taken in a group of patients in a randomised crossover study of both agents. The scans were scored to give a value for the stress and redistribution images and a reversibility score (redistribution--stress). All patients had coronary angiography that was also scored. Differences between the two agents were compared by a paired t test. PATIENTS--30 patients aged 51-70 years with chest pain thought to be caused by myocardial ischaemia. 11 had had previously myocardial infarction. RESULTS--Dipyridamole caused adverse symptoms in six patients whereas dobutamine caused symptoms in 21 patients (chi 2 = 15.15, p < 0.0001). Dobutamine stress took considerably longer than dipyridamole (31 v 6 minutes) and cost more (17 pounds v 1.50 pounds). There were no significant differences between the agents in terms of total stress or redistribution scores, but regional analysis showed that dipyridamole showed significantly more defects during stress at the apex and lateral wall (p < 0.05), with no significant difference at redistribution. Dipyridamole stress also caused significantly more reversible defects at the apex (p < 0.05) and gave a better correlation than dobutamine with coronary score (dipyridamole r = 0.80, p < 0.001 v dobutamine r = 0.64, p < 0.001). In six patients who had continued to take beta blockers the results of dobutamine stress did not correlate with coronary score, r = 0.34 (NS), whereas dipyridamole studies were not affected. CONCLUSION--Compared with dobutamine, dipyridamole was as effective in producing overall perfusion defects and more effective in provoking defects at the apex and lateral segment. The dipyridamole study correlated better with coronary score and was not affected by concurrent beta blocker treatment. It was also better tolerated by the patients, was less time consuming, and was much cheaper.     

Biological variation of urinary N-acetyl-beta-D-glucosaminidase: practical and clinical implications

The analytical, within-subject, and between-subject components of variation of N-acetyl-beta-D-glucosaminidase (NAG) were estimated from duplicate assays of 10 timed first morning and 10 untimed urine specimens collected from each of 15 ostensibly healthy individuals. Results were expressed in terms of activity, NAG/creatinine ratio, and excretion rate. Current analytical methods can achieve desirable performance standards. NAG has little individuality, and conventional population-based reference intervals are therefore useful. In view of the practicability and relatively low within-subject variation, for routine clinical purposes we prefer assay of NAG in first morning urine, expressing the results in terms of activity. Using the results of assays of different specimens, we found that the correlation between urinary albumin and NAG varied considerably, owing to the large intrinsic variability of both analytes; this might explain previous conflicting results.     

The effect of conceptual and contextual familiarity on transfer performance

Applying a previously learned concept to a novel problem is an important but difficult process called transfer. It is suggested that a commonsense analogy aids in transfer by linking novel concepts to familiar ones. How the context of practice affects transfer when learning using analogies is still unclear. This study investigated the effect of a commonsense analogy and context familiarity for transfer of physiological concepts. First year psychology students (n = 24) learned three concepts: Starling's law, Laplace's law, and laminar-turbulent flow. The control group saw standard explanations while the intervention group saw an additional commonsense analogy. The context of learning was the organ system used for two practice clinical cases which differed for all concepts. Testing consisted of 12 new clinical cases. Starling's law cases used the organ system from practice while the other concepts presented in both novel and familiar organ systems. Half of the sample repeated testing after 1 week delay. The outcome was ratings of explanations of cases on a 0-3 scale. The effect of analogy was significant (Mean = 1.24 with, 0.86 without, F(1,22) = 4.26, p < 0.05) but not after delay (means of 1.08 and 0.75 respectively, F = (1,10), p = 0.06) There was significant effect for familiar context (Same = 1.23 (Starling), different = 0.68 (Laplace) and 0.73 (laminar-turbulent flow) (F(2,44) = 5.14, p < 0.01). Laplace's law and laminar turbulent flow cases in the familiar organ system had means of 1.65 and 1.77 respectively compared to novel cases with means of 0.74 and 0.68 (F(1,22) = 35.64, p < 0.0001). Similar effects were observed after delay. There was significant decay in performance after delay for all participants (immediate = 1.17, delayed = 0.91, F = 11.9 (1,10) p < 0.01). Common analogies aid conceptual understanding necessary for transfer. Despite conceptual aids, solving transfer problems is difficult.     

Comparative fatigue strengths and stabilities of metacarpal internal fixation techniques

To study quantitative differences in the fatigue strength and stability obtained with 5 types of internal fixation of metacarpal fractures, 105 preserved human metacarpals were cyclically tested in bending, torsion, and axial loading after oblique osteotomies of the metacarpal and internal fixation. The dorsal plate with lag screw was superior in all modes, followed by the two dorsal lag screws, crossed Kirschner wire tension banding, and intramedullary Kirschner wire fixation. The five intramedullary and the paired intramedullary Kirschner wire fixations were not statistically different. The fatigue life of the plate fixation was significantly larger in bending (1.5 times), torsion (1.6 times), and axial loading (2.5 times) than the second strongest fixation, two dorsal lag screws. Its initial rigidity was significantly higher in axial loading (1.5 times) but was not statistically different in bending and torsion.     

Impact of pediatric nurses' uniforms on perceptions of nurse professionalism

This study examined the impact of nursing pants uniform color and style on perceptions of professionalism. Pediatric patients 7 to 17 years of age and their adult visitors were surveyed at two midwestern health care centers. Participants viewed eight photographs of the same RN in different uniforms. Adult participants rated each photograph for 10 image traits using a modified nurse image scale (MNIS). Pediatric participants rated each photograph for five image traits using the nurse image scale for children (NISC). Pediatric participant median sum scores for the eight uniforms were similar, despite clear preferences for boldly printed top and pressed blue or white-pant uniforms (22% each). Adult participant median sum scores were similar for six of the eight uniforms, but two had significantly lower scores (p < 0.001). Pediatric patients' and visitors' uniform preferences are not related to perceptions of professionalism.     

Increased proximal tubular reabsorption of sodium in childhood diabetes mellitus

Type 1 diabetes mellitus is associated with an increase in total exchangeable body sodium. To delineate a site of possible altered sodium handling, proximal tubular sodium reabsorption (PTRNa) was measured in 30 diabetic children, age 12.0 (range 7-16) yr, duration of diabetes 4.5 (range 0.2-12) yr, and compared with 10 non-diabetic children, age 10.0 (range 8.6-12.5) yr. PTRNa was calculated from the fractional clearance of lithium, which was determined from a single blood sample and a random untimed urine sample, taken between 0700 and 0830 h at home, fasting, before insulin therapy. PTRNa was significantly increased in the diabetic children compared with the non-diabetic children (81.6(SE 1.0) vs 74.2(2.6)%, p = 0.014). There was no relationship of PTRNa with age, duration of diabetes, metabolic control (glycosylated haemoglobin, plasma and urinary glucose, plasma lactate), or urinary protein excretion (albumin, N-acetyl-beta-D-glucosaminidase). Elevated sodium reabsorption in the proximal renal tubule may account for the high total exchangeable body sodium found in Type 1 diabetic patients.     

Reflecting on Diagnostic Errors: Taking a Second Look is Not Enough

BACKGROUND

An experimenter controlled form of reflection has been shown to improve the detection and correction of diagnostic errors in some situations; however, the benefits of participant-controlled reflection have not been assessed.

OBJECTIVE

The goal of the current study is to examine how experience and a self-directed decision to reflect affect the accuracy of revised diagnoses.

DESIGN

Medical residents diagnosed 16 medical cases (pass 1). Participants were then given the opportunity to reflect on each case and revise their diagnoses (pass 2).

PARTICIPANTS

Forty-seven medical Residents in post-graduate year (PGY) 1, 2 and 3 were recruited from Hamilton Health Care Centres.

MAIN MEASURES

Diagnoses were scored as 0 (incorrect), 1 (partially correct) and 2 (correct). Accuracies and response times in pass 1 were analyzed using an ANOVA with three factors—PGY, Decision to revise yes/no, and Case 1–16, averaged across residents. The extent to which additional reflection affected accuracy was examined by analyzing only those cases that were revised, using a repeated measures ANOVA, with pass 1 or 2 as a within subject factor, and PGY and Case or Resident as a between-subject factor.

KEY RESULTS

The mean score at pass 1 for each level was PGY1, 1.17 (SE 0.50); PGY2, 1.35 (SE 0.67) and PGY3, 1.27 (SE 0.94). While there was a trend for increased accuracy with level, this did not achieve significance. The number of residents at each level who revised at least one diagnosis was 12/19 PGY1 (63 %), 9/11 PGY2 (82 %) and 8/17 PGY3 (47 %). Only 8 % of diagnoses were revised resulting in a small but significant increase in scores from Pass 1 to 2, from 1.20/2 to 1.22 /2 (t = 2.15, p = 0.03).

CONCLUSIONS

Participants did engage in self-directed reflection for incorrect diagnoses; however, this strategy provided minimal benefits compared to knowing the correct answer. Education strategies should be directed at improving formal and experiential knowledge.

Electronic supplementary material

The online version of this article (doi:10.1007/s11606-015-3369-4) contains supplementary material, which is available to authorized users.KEY WORDS: clinical reasoning, diagnostic error, reflection