Biomedical subjects
S Hahn
Publications and source records attributed to S Hahn.
Evidence of reference standard related bias in studies of plain radiograph reading performance: a meta-regression.
The aim is to determine the effect of reference standard related bias on estimates of plain radiograph reading performance using studies conducted in clinical practice. Data were extracted on study eligibility, clinical and reference standard characteristics and reading performance. The choice of reference standards and the prevalence of bias are presented descriptively. Associations between bias and reading performance are estimated using a regression model that produces relative diagnostic odds ratios (RDOR) with 95% confidence intervals (CIs). Three of the 20 eligible studies addressed all five reference standard related biases; 15 studies addressed three or more. When the reference standard report is influenced by knowledge of an observer's opinion this is associated with a significant overestimation in reading performance (RDOR, 3.7; 95% CI, 1.6 to 8.3; p = 0.01). There is limited evidence that reading performance is inflated when the observer is aware of the reference standard report before commenting on the radiograph (RDOR, 1.7; 95% CI, 0.6 to 5.1) and deflated when a less valid reference standard is used (RDOR, 0.5; 95% CI, 0.1 to 2.5). There is no evidence that reading performance is affected by application of the reference standard depending on an observer's opinion and using different reference standards in the same study. In conclusion we found variation in the choice and application of reference standards in studies of plain radiograph reading performance, but only when reference standards report in the knowledge of an observer's opinion does this contribute to a significant overestimation in reading performance.
Accuracy of radiographers red dot or triage of accident and emergency radiographs in clinical practice: a systematic review.
AIM: To determine the accuracy of radiographers red dot or triage of accident and emergency (A&E) radiographs in clinical practice. MATERIALS AND METHODS: Eligible studies assessed radiographers red dot or triage of A&E radiographs in clinical practice compared with a reference standard and provided accuracy data to construct 2 x 2 tables. Data were extracted on study eligibility and characteristics, quality, and accuracy. Pooled sensitivities and specificities and chi-square tests of heterogeneity were calculated. RESULT: Three red dot and five triage studies were eligible for inclusion. Radiographers' red dot of A&E radiographs in clinical practice compared with a reference standard is 0.87 [95% confidence interval (CI) 0.85-0.89] and 0.92 (0.91-0.93) sensitivity and specificity, respectively. Radiographers' triage of A&E radiographs of the skeleton is 0.90 (0.89-0.92) and 0.94 (0.93-0.94) sensitivity and specificity, respectively; and for chest and abdomen is 0.78 (0.74-0.82) and 0.91 (0.88-0.93). Radiographers' red dot of skeletal A&E radiographs without training is 0.71 (0.62-0.79) and 0.96 (0.93-0.97) sensitivity and specificity, respectively; and with training is 0.81 (0.72-0.87) and 0.95 (0.93-0.97). Pooled sensitivity and specificity for radiographers without training for the triage of skeletal A&E radiographs is 0.89 (0.88-0.91) and 0.93 (0.92-0.94); and with training is 0.91 (0.88-0.94) and 0.95 (0.93-0.96). CONCLUSION: Radiographers red dot or triage of A&E radiographs in clinical practice is affected by body area, but not by training.
[Recent advances in prenatal diagnostics].
During the last years, technical improvements have increased the possibilities in prenatal ultrasound. During the eighties and nineties, fetal malformations were increasingly detected and specified. Since a few years, the measurement of the fetal nuchal translucency between 11 and 14 weeks of gestation has been implemented to calculate the individual risk, in combination with most recent biochemical markers. Today, the sonographic measurement of the nuchal translucency is regarded as a valuable screening tool for chromosomal anomalies in prenatal medicine. Beside standardized examinations, a profound information and counseling of the pregnant women should be emphasized. With the improvement of the specific maternal risk calculation, using the sonographic measurement of the nuchal translucency, the biochemical markers and the maternal age, unnecessary invasive examinations may be prevented and their overall number can significantly be reduced. The same trend is seen in the whole field of prenatal medicine, illustrated by the detection of the fetal rhesus D status from the maternal blood and the use of Doppler ultrasound in the management of fetal anemia.
A comparative evaluation of two different approaches to estimating age at adiposity rebound.
OBJECTIVE: To compare different approaches (visual estimation of individual BMI curves with polynomial models) to estimate age at adiposity rebound (AR), as different approaches might lead to different results. AR has been suggested as a critical period between intra-uterine life and early adulthood, and recent data showed that early age at AR is associated with higher body mass later in life. METHODS: Longitudinal anthropometric data from the DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study were used to obtain individual BMI growth curves. We then compared the visual estimation approach to polynomial models in three different scenarios reflected by different data sets: an idealistic, an realistic, and a realistic scenario with imputed values. RESULTS: In all three scenarios, the visual estimation yielded significantly higher estimates than the polynomial models of 2nd or 3rd order. Cross-tabulations of groups of age at AR (early, medium, and late) showed that truly concordant classification was low, ranging only from 51 to 63%. A closer examination of the data indicated that the differences in estimates were mainly due to differences in the underlying definitions: the polynomial models select the nadir in the growth curve as the age at AR, whereas the visual estimation deviates from this concept in those cases where there is plateau in the growth curve. In the latter instance, the turning point of the growth curve before its increase is selected as the age at rebound. CONCLUSIONS: Estimating AR with the visual approach appears to best reflect the physiological basis of the AR, and is also preferable, because it resulted in the lowest number of children with missing estimates for age at AR. Only when the underlying criteria for the estimation of AR with the visual approach were modified, could concordant results between the two approaches be obtained. Considering the underlying physiological basis, it became clear that approaches which determine AR by simply identifying the nadir in the BMI curve do not reflect AR appropriately. This refers to those cases in which the nadir in the growth curve and the turning point at the onset of the adiposity increase are not identical.
The combination of increased ovarian volume and follicle number is associated with more severe hyperandrogenism in German women with polycystic ovary syndrome.
The prevalence and relevance of polycystic ovaries (PCO) in German women with polycystic ovary syndrome has not been evaluated. This retrospective study included 212 PCOS patients (mean age 28 years) diagnosed by the NIH-criteria and consecutively recruited since 2003. Clinical features including anthropometric variables and the degree of hirsutism, family history, menstrual cyclicity as well as endocrine biochemical parameters were recorded. In addition, 3-h oral glucose tolerance testing for indices of insulin resistance and glucose metabolism was performed in each patient. Transvaginal ultrasound was used to detect polcystic ovaries, defined as the presence of at least one ovary > 10 ml or with at least 12 follicles of 2-9 mm diameter. In this German PCOS cohort, PCO were identified in 166 women (78%). Women with PCO (PXO+) had significantly higher LH/FSH ratios (median 2.1 vs. 1.7) and IGF-1 levels (median 182.5 vs. 160.5 ng/ml) compared to patients without PCO (PCO-). In addition, a significantly higher prevalence of acne (50% vs. 33%) and higher hirsutism scores (median 9 vs. 7) were found in PCO+ patients. Testosterone levels and the free androgen index (FAI) correlated significantly with ovarian volume and the number of ovarian follicles. Also, a subgroup of PCO+ women with a combination of increased ovarian volume and follicle number had higher testosterone levels (median 3.1 vs. 2.1 nmol/l) and FAI (median 7.6 vs. 4.5) compared to women with increased follicle count but normal volume. No differences were found in metabolic parameters or insulin resistance indices. PCO are common finding in German PCOS women. PCO appear to be associated with a more pronounced hyperandrogenemia, especially when both ovarian volume and follicle number are increased.
Impact of smoking on the course of Graves' disease after withdrawal of antithyroid drugs.
Cigarette smoking has been reported to alter relapse rate in patients with Graves' disease (GD). However, the predictive effect of smoking in GD patients after withdrawal of antithyroid drug treatment (ATDT) is still controversial. A prospective multicenter trial has previously identified smoking as an independent risk factor for relapse. Based on this study, the present paper gives a more detailed analysis of the impact of smoking on the long-term course of GD after ATDT withdrawal. To this end, 86 smokers and 177 non-smokers were followed during two years after ATDT cessation. At the end of ATDT (visit 1) and four weeks later (visit 2) smokers had significant higher TSH receptor antibody (TRAb) levels than non-smokers (10.0 IU/L+/-1.6; mean+/-SEM vs. 6.4 IU/L+/-0.9; 11.0 IU/L+/-1.8 vs. 6.8 IU/L+/-0.8, p < 0.01, respectively). During follow-up, Kaplan Meier analysis showed a significantly higher relapse rate in smokers than non-smokers. A subset of GD patients with TRAb levels >10 IU/L had the highest risk to develop relapse during follow-up. Among them, smokers more often relapsed than non-smokers irrespective of TRAb levels, p < 0.01. Thus, in smokers with TRAb levels > or =10 IU/L the predictive values of a positive and negative test for relapse was 68% and 73%, respectively (specificity 95%). In conclusion, we identified two effects by which smoking alters the course of GD. First, smoking is implicated to elevate TRAb levels and therefore increase the risk for relapse during follow-up. Second, smoking is an independent risk factor to worsen the clinical course of both, GD patients with low and high immunological risk to experience relapse after a successful outcome of ATDT. Thus, our data suggest that smoking has modifying immunological consequences and an adverse impact on the course of GD after withdrawal of ATDT. Therefore, patients should be encouraged to stop smoking.
Gadolinium as an alternative contrast agent during cardiac catheterization in patient with iodine-induced hyperthyroidism.
We report the first case of a male patient with iodine-induced hyperthyroidism and unstable angina pectoris in whom a diagnostic cardiac catheterization with gadolinium as contrast agent was chosen. The patient was hospitalized with an iodine-induced hyperthyroidism after angioplasty using an iodinated contrast agent. He presented with a continuous arrhythmia and unstable angina pectoris. A repeated cardiac catheterization using iodinated contrast agent was contraindicated. This case report shows that gadolinium is a useful alternative contrast agent for cardiac intervention in patients with iodine-induced hyperthyroidism.
Low serum 25-hydroxyvitamin D concentrations are associated with insulin resistance and obesity in women with polycystic ovary syndrome.
Insulin resistance (IR) and central obesity are common features of the polycystic ovary syndrome (PCOS). Vitamin D is thought to play a role in the pathogenesis of type 2 diabetes by affecting insulin metabolism. The aim of our study was to investigate the effect of 25-hydroxyvitamin D (25-OH-VD) on metabolic parameters and IR in PCOS. In 120 untreated PCOS patients (median age 28 years) levels of 25-OH-VD (radioimmunoassay method provided by DiaSorin), calcium and anorganic phosphate were measured. In addition, endocrine and metabolic variables were evaluated and a glucose tolerance test was performed to assess indices of IR. In the entire PCOS cohort, 25-OH-VD concentrations were negatively correlated with body mass index (r=-0.2765), body fat (r=-0.2490), HOMA-IR (r=-0.1947), hyperinsulinemia (r=-0.1892) and leptin levels (r=-0.2834), and positively correlated with HDL cholesterol (r=0.2630) (all p<0.05). Subgroup analysis of lean, overweight and obese women revealed significant higher 25-OH-VD levels in lean women. Differences remained significant when women were divided according to their 25-OH-VD levels. Women with hypovitaminosis D (<9 ng/ml) had higher mean BMI, indices of IR and leptin levels compared to women with normal serum levels (all p<0.05). Analysis of vitamin D and biochemical endocrine PCOS features revealed a significant correlation only between 25-OH-VD and sex hormone-binding globulin as well as the free androgen index. In conclusion, in PCOS women, low 25-OH-VD levels are associated with obesity and insulin resistance but not with PCOS per se.
The effect of a training course on mental health nurses' attitudes on the reasons of patient aggression and its management.
Aggression in healthcare systems poses a major problem for nurses because they are the most susceptible to suffer violence. Studies demonstrate that attitudes of nurses influence their behaviour regarding aggression and violence. Training programmes can positively change nurses' attitudes. This quasi-experimental study aimed to examine the effects of a systematic training course in aggression management on mental health nurses' attitudes about the reasons for patients' aggression and on its management. Sixty-three nurses (29 in the intervention and 34 in the control group) participated in this quasi-experimental pre-test and post-test study. The attitude of the participants of a training course was recorded by the German version of the Management of Aggression and Violence Attitude Scale (MAVAS). No significant attitude changes occurred in the intervention group at post-test. It is concluded that trainings intending to influence attitudes regarding the reason for patient aggression should consider the impact of the pedagogical quality of the training course, organizational support, and the user's perception. Moreover, it remains questionable to what extent a single instrument of measurement can record attitude changes.
Aberrations of early trophoblast differentiation predispose to pregnancy failure: lessons from the anti-phospholipid syndrome.
OBJECTIVES: The epithelium of the human placenta comprises an inner cytotrophoblast (CT) which proliferates and fuses with the outer differentiated syncytiotrophoblast (ST). Turnover has been studied focussing on second and third trimester placentas but with a paucity of data describing the normal first trimester trophoblast. The aim of this study was to compare the nuclear CT:ST ratio in normal and pathological pregnancy and thus establish the relationship between cytotrophoblast and syncytiotrophoblast nuclear number during early gestation. METHODS: Archival first trimester material from placentas from healthy pregnancy and recurrent miscarriage (anti-phospholipid syndrome) was stained with H&E, cytokeratin-7 and Mib-1. The area of trophoblast as a fraction of total villous area was calculated and the number of sectioned cytotrophoblast and syncytiotrophoblast nuclei as well as the number of proliferating cytotrophoblast was evaluated. RESULTS: Normal features of trophoblast development during the first trimester (rise in trophoblast area, increase in number of syncytiotrophoblast nuclei, increase in number of proliferating cytotrophoblast, decrease in the nuclear CT:ST ratio) are absent/reversed in tissues from recurrent miscarriage (decreasing trophoblast area, constant number of syncytiotrophoblast nuclei, decreasing number of proliferating trophoblast, constant nuclear CT:ST ratio). CONCLUSIONS: Proliferation of cytotrophoblast in early gestation provides a pool of trophoblast stem cells critical for ongoing placental development. Premature cytotrophoblast differentiation in favour of syncytial fusion results in deficiencies of cytotrophoblast and rarification of villous trophoblast. Abnormal trophoblast differentiation in early gestation may be due to a premature onset of maternal perfusion of the placenta and may be a likely antecedent for conditions associated with failure of placentation such as recurrent miscarriage.
The use of unequal randomisation ratios in clinical trials: a review.
OBJECTIVE: To examine reasons given for the use of unequal randomisation in randomised controlled trials (RCTs). MAIN MEASURES: Setting of the trial; intervention being tested; randomisation ratio; sample size calculation; reason given for randomisation. METHODS: Review of trials using unequal randomisation. DATABASES AND SOURCES: Cochrane library, Medline, Pub Med and Science Citation Index. RESULTS: A total of 65 trials were identified; 56 were two-armed trials and nine trials had more than two arms. Of the two-arm trials, 50 trials recruited patients in favour of the experimental group. Various reasons for the use of unequal randomisation were given. Six studies stated that they used unequal randomisation to reduce the cost of the trial, with one screening trial limited by the availability of the intervention. Other reasons for using unequal allocation were: avoiding loss of power from drop-out or cross-over, ethics and the gaining of additional information on the treatment. Thirty seven trials papers (57%) did not state why they had used unequal randomisation and only 14 trials (22%) appeared to have taken the unequal randomisation into account in their sample size calculation. CONCLUSION: Although unequal randomisation offers a number of advantages to trials the method is rarely used and is especially under-utilised to reduce trial costs. Unequal randomisation should be considered more in trial design especially where there are large differences between treatment costs.
Usefulness of the carina as a radiographic landmark for central venous catheter placement in paediatric patients.
BACKGROUND: Several reports have proposed radiographic landmarks for the proper positioning of central venous catheters (CVC). The carina is one of the proposed landmarks in adults. Here, we evaluate the possibility of using the carina as a radiographic landmark for the identification of proper positioning of the CVC tip in paediatric patients. METHODS: We studied 57 right internal jugular vein catheterizations in infants and children undergoing surgery for the treatment of congenital heart disease. After placing the CVC tip at the junction of the superior vena cava and the right atrium (SVC-RA junction) via intraoperative transoesophageal echocardiography, and by taking postoperative anterior-posterior chest radiographs, we measured the longitudinal distance from the carina to the SVC-RA junction, using the Picture Archiving and Communicating System. RESULTS: The average distance between the carina and the SVC-RA junction was 1.5 cm (95% CI 1.3-1.8 cm). No catheter tip was above the carina. Although there was no particular relationship between this distance and the patient's age, height, or weight, the distance between the carina and the SVC-RA junction tended to be more variable in younger and smaller children. CONCLUSIONS: The carina can be used as a radiographic landmark for the proper CVC tip placement in paediatric patients. If the tip of the CVC is not distal to the carina the chances are minute that it is in the right atrium.
Anticipation in familial pancreatic cancer.
BACKGROUND: Previous studies of anticipation in familial pancreatic cancer have been small and subject to ascertainment bias. Our aim was to determine evidence for anticipation in a large number of European families. PATIENTS AND METHODS: A total of 1223 individuals at risk from 106 families (264 affected individuals) were investigated. Generation G3 was defined as the latest generation that included any individual aged over 39 years; preceding generations were then defined as G2 and G1. RESULTS: With 80 affected child-parent pairs, the children died a median (interquartile range) of 10 (7, 14) years earlier. The median (interquartile range) age of death from pancreatic cancer was 70 (59, 77), 64 (57, 69), and 49 (44, 56) years for G1, G2, and G3, respectively. These indications of anticipation could be the result of bias. Truncation of Kaplan-Meier analysis to a 60 year period to correct for follow up time bias and a matched test statistic indicated significant anticipation (p=0.002 and p<0.001). To minimise bias further, an iterative analysis to predict cancer numbers was developed. No single risk category could be applied that accurately predicted cancer cases in every generation. Using three risk categories (low with no pancreatic cancer in earlier generations, high with a single earlier generation, and very high where two preceding generations were affected), incidence was estimated without significant error. Anticipation was independent of smoking. CONCLUSION: This study provides the first strong evidence for anticipation in familial pancreatic cancer and must be considered in genetic counselling and the commencement of secondary screening for pancreatic cancer.
Accuracy of radiographer plain radiograph reporting in clinical practice: a meta-analysis.
AIM: To determine the accuracy of radiographer plain radiograph reporting in clinical practice. MATERIALS AND METHODS: Studies were identified from electronic sources and by hand searching journals, personal communication and checking reference lists. Eligible studies assessed radiographers' plain radiograph reporting in clinical practice compared with a reference standard, and provided accuracy data to construct 2 x 2 contingency tables. Data were extracted on study eligibility and characteristics, quality and accuracy. Summary estimates of sensitivity and specificity and receiver operating characteristic curves were used to pool the accuracy data. RESULTS: Radiographers compared with a reference standard, report plain radiographs in clinical practice at 92.6% (95% CI: 92.0-93.2) and 97.7% (95% CI: 97.5-97.9) sensitivity and specificity, respectively. Studies that compared selectively trained radiographers and radiologists of varying seniority against a reference standard showed no evidence of a difference between radiographer and radiologist reporting accuracy of accident and emergency plain radiographs. Selectively trained radiographers were also found to report such radiographs as accurately as those not solely from accident and emergency, although some variation in reporting accuracy was found for different body areas. Training radiographers improved their accuracy when reporting normal radiographs. CONCLUSION: This study systematically synthesizes the literature to provide an evidence-base showing that radiographers can accurately report plain radiographs in clinical practice.
Radiographers and radiologists reporting plain radiograph requests from accident and emergency and general practice.
AIM: To assess selectively trained radiographers and consultant radiologists reporting plain radiographs for the Accident and Emergency Department (A&E) and general practitioners (GPs) within a typical hospital setting. METHODS: Two radiographers, a group of eight consultant radiologists, and a reference standard radiologist independently reported under controlled conditions a retrospectively selected, random, stratified sample of 400 A&E and 400 GP plain radiographs. An independent consultant radiologist judged whether the radiographer and radiologist reports agreed with the reference standard report. Clinicians then assessed whether radiographer and radiologist incorrect reports affected confidence in their diagnosis and treatment plans, and patient outcome. RESULTS: For A&E and GP plain radiographs, respectively, there was a 1% (95% confidence interval (CI) -2 to 5) and 4% (95% CI -1 to 8) difference in reporting accuracy between the two professional groups. For both A&E and GP cases there was an 8% difference in the clinicians' confidence in their diagnosis based on radiographer or radiologist incorrect reports. For A&E and GP cases, respectively, there was a 2% and 8% difference in the clinicians' confidence in their management plans based on radiographer or radiologist incorrect reports. For A&E and GP cases, respectively, there was a 1% and 11% difference in effect on patient outcome of radiographer or radiologist incorrect reports. CONCLUSION: There is the potential to extend the reporting role of selectively trained radiographers to include plain radiographs for all A&E and GP patients. Further research conducted during clinical practice at a number of sites is recommended.
A comparative study of the effect of three different syncytiotrophoblast micro-particles preparations on endothelial cells.
Pre-eclampsia is a pregnancy-associated multi-system disorder of unknown etiology, characterized by damage to the maternal endothelium. The latter facet has been suggested to be mediated in part by elevated shedding of inflammatory placental syncytiotrophoblast micro-particles (STBM) into the maternal circulation. In this study, we have examined STBM prepared by three different methods: mechanical dissection, in vitro placental explant culture and perfusion of placental cotyledons. All three preparations yielded morphologically similar STBM, as confirmed by scanning electron microscopy, and all contained syncytiotrophoblast-specific proteins as determined by the presence of placental alkaline phosphatase. The functional properties of the three STBM preparations were examined on human umbilical vein endothelial cells (HUVEC), where the mechanically prepared particles were found to inhibit proliferation to the greatest extent. Furthermore, only mechanically prepared STBM lead to the detachment and apoptosis of HUVEC cells. Our study, therefore, suggests that STBM prepared from placental perfusion or in vitro explant culture are biologically different from mechanically prepared ones, and may provide a better approximation of physiologically produced placental micro-particles.
Differences between recumbent length and stature measurement in groups of 2- and 3-y-old children and its relevance for the use of European body mass index references.
OBJECTIVE: To compare length and stature measurements of young children and to examine the relevance of any difference for comparison with body mass index (BMI) references designed for use from birth to adulthood. SUBJECTS: A total of 426 2-y-old and 525 3-y-old children included in the Dortmund Nutritional and Anthropometrical Longitudinally Designed (DONALD) Study. DATA ANALYSIS: Length and stature were measured to the nearest millimetre using a stadiometre. Agreement between both measurements at age 2 and 3 y, respectively, was determined by mean differences and by comparison with the German BMI reference. RESULTS: The average length of 2-y-old girls and boys was 88.3 (3.1) and 89.9 (3.2) cm, mean differences (stature minus length) were -0.47 (0.65) and -0.45 (0.64) cm. The corresponding BMI values were 16.18 (1.3) and 16.46 (1.2) kg/m2, with mean differences of +0.17 (0.24) and +0.16 (0.23). According to stature, 9.4% of the girls and 10.8% of the boys were overweight (>90th percentile), while length classified 7.1 and 9.4% as overweight. Similar mean differences between length and stature were observed at age 3 y: -0.53 (0.62) and -0.47 (0.65) cm in height and +0.17 (0.20) and +0.14 (0.20) kg/m2 in the BMI of girls and boys, respectively. According to stature, 7.6 and 7.3% were overweight as opposed to 5.4 and 4.8% using length. The observed differences increased with higher BMI levels. CONCLUSION: Changing measurements from length to stature results in an upward shift of BMI, not reflected in current European BMI references. This small but systematic error may result in misinterpretation of individual BMI levels or trend observations.