Clinical trial designs--made to order

At times, clinical trial design presents difficult problems for the consulting statistician. The nature of the disease under study or the inadequacies of standard methodology often suggest alternative strategies for the development of useful clinical trial designs. This paper examines two case of novel clinical trial designs that are "made-to-order" for the problem at hand. Both address disease-specific issues. The first case considers the use of adaptive allocation of treatments to patients in a trial in major depressive disorder. The second case reviews the design of a novel efficacy parameter in advanced pancreatic cancer.     

Microvascular transplantation in the salvage of lower extremity trauma in the elderly

In the cadaver of an 86 year old man the inferior segment of the azygos vein could not be found. Furthermore, a normally developed hemiazygos vein drained the right and left intercostal veins from T 10 to T 6. This vessel finally curved towards the right to reach the superior vena cava after having drained the right superior intercostal veins. The left superior intercostal vein ended in a short vessel draining into the left brachiocephalic vein. This condition may be represented in a standard chest radiograph by the so-called "aortic nipple". Agenesis of the azygos vein, suspected because of the presence of this radiological sign, should be confirmed in the living by means of computerized tomography. This can clarify the anatomy of the mediastinal vessels precisely. Embryological pattern of the azygos system accounting for its possible defects is discussed.     

A novel method for replacement of the dislodged tracheostomy tube: the nasogastric tube "guidewire" technique

The ready access to blood (plasma and formed cellular elements) makes it unusually susceptible to the deleterious effects of pollutants whose origins may be in the air. The red blood cells' hemoglobin may be rendered useless for oxygen transport by combination with carbon monoxide or conversion to methemoglobin or sulfhemoglobin. Lead and arsine can damage the erythrocytes' membranes, resulting in anemia. Metabolites of benzene and other volatile polycyclic hydrocarbons are implicated in the causation of leukemias. The extensive use of pesticides and herbicides may be associated with the development of Hodgkin's disease, non-Hodgkin's lymphoma, and aplastic anemia. The carcinogenic risks from ionizing radiation, especially for leukemia, are well known. More information is needed concerning the epidemiology of environmental factors responsible for damage to blood. Enhanced knowledge about the molecular biology of toxins' effects on the hematopoietic system and improved detection and prevention technologies are needed to answer environmentally related health questions.     

Epithelial marker genes are expressed in cultured embryonic rat lung and in vivo with similar spatial and temporal patterns

Explants of embryonic lung are often used to characterize lung growth, bronchial tree pattern, and cell differentiation. Most investigators culture lungs for 3-7 days in defined media lacking, e.g., added growth factors or hormones. If growth and differentiation are comparable to that in vivo, these cultures show considerable promise for identifying developmental regulatory molecules and target genes, and for elucidating molecular responses. We used in situ hybridization and RT-PCR to compare times and sites of expression of mRNAs of six epithelial genes in cultured and uncultured fetal rat lungs. These genes, expressed in distal lung of adult rats, are surfactant proteins (SP) A, B, and C; LAR, a receptor-type tyrosine phosphatase; Clara cell secretory protein (CC10, CCSP); and T1alpha. SP-A, SF-B, LAR, and CC10 are expressed by both Clara and Type II cells in adult animals. SP-C and T1alpha are unique markers for Type II and Type I cells, respectively. SP-C, LAR, and T1alpha are expressed before the lung is explanted (Day 13.5); SP-A, -B, and CC10 mRNAs are first detected later. The onset of expression is similar in vivo and in vitro. Although the patterns of expression differ for each mRNA, their sites of expression in culture match those in vivo relative to the bronchial tree. The explanted embryonic lung appears to be an excellent experimental model.     

Persistent thrombin generation in humans during specific thrombin inhibition with hirudin

BACKGROUND: The degree to which antithrombotic drugs suppress thrombin generation is unknown. Because hirudin, unlike antithrombin III, binds intravascular thrombin rapidly and selectively to yield a circulating inactive complex of 3- to 4-hour half-life, we used intravenous hirudin in humans to investigate the course of thrombin generation during and early after anticoagulation with this potent, direct antithrombin. METHODS AND RESULTS: Intravascular thrombin was measured with an ELISA for the thrombin-hirudin complex formed during and for 18 hours after stopping a 6-hour infusion of hirudin at 0.1, 0.2, and 0.3 mg.kg-1.h-1 in three groups of six patients each. With free hirudin in 20- to 10,000-fold molar excess of thrombin and peak activated partial thromboplastin times of 2.3 to 3.0 times baseline, mean plasma thrombin-hirudin complex increased from 794 +/- 85 pg/mL (mean +/- SEM) 15 minutes after the start of the infusion to 1617 +/- 151 pg/mL at 6 hours of infusion to 2667 +/- 654 pg/mL at 24 hours. During the 24-hour observation period, plasma concentration of fragment 1.2 (the peptide released during conversion of prothrombin to thrombin) never fell below baseline but rather increased transiently during the hirudin infusion. Plasma concentrations of thrombin-antithrombin III complex (in ng/mL) decreased from 4.34 +/- 0.40 at baseline to 1.64 +/- 0.13 at 6 hours (P < .001) and gradually increased after stopping the infusion to 5.7 +/- 0.87 at 24 hours (nonsignificant compared with baseline). CONCLUSIONS: Measurement of thrombin-hirudin complex may be used as a marker of thrombin generation in humans. Persistent accumulation of thrombin-hirudin complex and generation of fragment 1.2 during and after completion of potent anticoagulation with hirudin suggest thrombin generation is not blocked by high-affinity thrombin inhibition. The persistent formation of thrombin during declining plasma levels of hirudin may contribute to the pathogenesis of rethrombosis early after antithrombin therapy or during inadequate anticoagulation.     

Epilepsy in very preterm infants: neonatal cranial ultrasound reveals a high-risk subcategory

Osteoporotic fractures, and in particular, hip fractures result in significant morbidity and mortality. Low bone mass is the main risk factor of enhanced bone fragility, resulting in an increased risk for hip fracture. Bone density of osteoporotic women with and without hip fractures show a considerable overlap. Therefore, other bone-independent factors also play an important role for the development of hip- and other osteoporotic fractures. One other important factor is falling. In 90% of hip fractures falling was involved [10-15], but only 5% or less of these falls resulted in a subsequent fracture. The view that adequate exercise is beneficial for skeletal health of children and for prevention and treatment of osteoporosis in adults is supported primarily by two lines of evidence: longitudinal and cross-sectional trials in children and young adult athletes showing a significant increase of muscle- and bone mass after strenuous (children) or chronic exercise (athletes) as compared to normally active (children) or sedentary control subjects. What are the potential benefits and limits of specific exercise programs with respect to bone mass, prevention of falls and fractures? In this review these questions are discussed and a specific exercise program in osteoporotic patients with fractures is delineated.     

Effect of various lipid-bile salt mixed micelles on the intestinal absorption of amphotericin-B in rat

We investigated the effect of the somatosensory functions to the outcomes of motor functions in 28 patients with thalamic hemorrhage. The disturbance of the pyramidal tracts was assessed by the destruction of the internal capsule found in computed tomography (CT). The disturbance of the somatosensory function was analyzed by the N20 component of short-latency somatosensory evoked potentials (SSEP). The outcomes of motor function was evaluated after 3 months of ictus. Correlations between the outcomes of motor function, disturbance of the pyramidal tract, and disturbance of the somatosensory function were discussed. The result indicated that functional outcomes statistically correlated with neither disturbance of the internal capsule alone nor disturbance of N20 alone. But, there was statistically significant between functional outcomes and the combination of disturbance of the internal capsule with disturbance of N20 (p < 0.05, Wilcoxon signed-rank). There was not statistical difference in hematoma volume or consciousness. The implications of these results suggest that somatosensory function may affect the recovery of motor functions.     

One world, one hope: the cost of providing antiretroviral therapy to all nations

OBJECTIVE: To estimate the potential direct cost of making triple combination antiretroviral therapy widely available to HIV-positive adults and children living in countries throughout the world. METHODS: For each country, antiretroviral costs were obtained by multiplying the annual cost of triple antiretroviral therapy by the estimated number of HIV-positive persons accessing therapy. Per capita antiretroviral costs were computed by dividing the antiretroviral costs by the country's total population. The potential economic burden was calculated by dividing per capita antiretroviral costs by the gross national product (GNP) per capita. All values are expressed in 1997 US dollars. RESULTS: The potential cost of making triple combination antiretroviral therapy available to HIV-positive individuals throughout the world was estimated to be over US$ 65.8 billion. By far the greatest financial burden was on sub-Saharan Africa. The highest per capita drug cost in this region would be incurred in the subregions of Southern Africa (US$ 149) followed by East Africa (US$ 116), Middle Africa (US$ 44), and West Africa (US$ 42). In the Americas, subregional data indicated the highest per capita drug cost would be in the Latin Caribbean (US$ 22), followed by the Caribbean (US$ 17), Andean Area (US$ 7), the Southern Cone (US$ 6), North America (US$ 6), and Central American Isthmus (US$ 5). In Asia and Europe the percentage of the GNP necessary to finance drug therapy was less than 1% in most countries examined. CONCLUSION: Our results demonstrate that the cost of making combination antiretroviral therapy available worldwide would be exceedingly high, especially in countries with limited financial resources.     

The Dental Subscale of the Children's Fear Survey Schedule: a factor analytic study in The Netherlands

The Dental Subscale of the Children's Fear Survey Schedule (CFSS-DS) is a well-known instrument for assessing dental fear in children. Previous studies have shown that the scale has acceptable reliability and validity. Factor analysis using scores of a group of Finnish schoolchildren resulted in three factors. No other data on the factor structure have been published. In order to report on the factor structure of the Dutch parental version of the CFSS-DS, the present study was undertaken. Factor analysis using scores from a group of Dutch children (n= 150) demonstrated a factor pattern fairly similar to the results found in the Finnish study. Three factors were found: 1) fear of highly invasive dental procedures, 2) fear of less invasive aspects of treatment and 3) fear of medical aspects. Considering that almost all items load substantially (> or =0.20) on more than one factor, it seems that one primary underlying dimension exists: fear of invasive treatment aspects. The CFSS-DS is proposed as a reliable, one-dimensional measure of dental fear.