Generalizing boundaries for triangular designs, and efficacy estimation at extended follow-ups

Background

Visceral leishmaniasis (VL) is a parasitic disease transmitted by sandflies and is fatal if left untreated. Phase II trials of new treatment regimens for VL are primarily carried out to evaluate safety and efficacy, while pharmacokinetic data are also important to inform future combination treatment regimens. The efficacy of VL treatments is evaluated at two time points, initial cure, when treatment is completed and definitive cure, commonly 6 months post end of treatment, to allow for slow response to treatment and detection of relapses.

This paper investigates a generalization of the triangular design to impose a minimum sample size for pharmacokinetic or other analyses, and methods to estimate efficacy at extended follow-up accounting for the sequential design and changes in cure status during extended follow-up.

Methods

We provided R functions that generalize the triangular design to impose a minimum sample size before allowing stopping for efficacy. For estimation of efficacy at a second, extended, follow-up time, the performance of a shrinkage estimator (SHE), a probability tree estimator (PTE) and the maximum likelihood estimator (MLE) for estimation was assessed by simulation.

Results

The SHE and PTE are viable approaches to estimate an extended follow-up although the SHE performed better than the PTE: the bias and root mean square error were lower and coverage probabilities higher.

Conclusions

Generalization of the triangular design is simple to implement for adaptations to meet requirements for pharmacokinetic analyses. Using the simple MLE approach to estimate efficacy at extended follow-up will lead to biased results, generally over-estimating treatment success. The SHE is recommended in trials of two or more treatments. The PTE is an acceptable alternative for one-arm trials or where use of the SHE is not possible due to computational complexity.

Trial registration

NCT01067443, February 2010.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-015-1018-1) contains supplementary material, which is available to authorized users.

Nix H, R. Margules C, F. Hutchinson M, A. Walker P, West J, L. Stein J, L. Kesteven J, Allison A, Natera G. The BioRap Biodiversity Assessment and Planning Study for Papua New Guinea

Papua New Guinea (PNG) has an incredible variety of land and marine ecosystems, including many components of biodiversity that are unique in the world. PNG's land mass constitutes less than one percent of the world's land area, yet estimates suggest that the country has more than 5% of the world's biodiversity. PNG has been recognized therefore as an important region for biodiversity conservation (see Alcorn 1993; Beehler 1993 and references within). Recently, Conservation International (CI) has recognized PNG as one of the small number of critical tropical forest areas for conservation efforts. That priority reflects not just PNG's unique biodiversity but also the fact that sustainable use of PNG's natural resources has become an important issue, particularly relating to its large mineral deposits, oil and natural gas reserves, agricultural potential, and forestry production potential. CI's perspective highlights important principles of conservation priority. PNG, like the other tropical wilderness areas on its priority list, is regarded as an opportunity for effective conservation at relatively low cost, given that these wilderness regions are still largely intact and have low human population density. In our view, realizing such opportunities requires good planning. Biodiversity conservation in PNG can imply low realized opportunity costs or quite high realized opportunity costs, depending on whether biodiversity planning is used to find a balance among society's competing needs through tradeoffs. PNG is a region worthy of urgent conservation planning attention because potential high net benefits for society may be needlessly foreclosed through inefficient planning that does not address conflicts among various needs of society. The risk of losing those potential net benefits is a strong argument for conservation investment in PNG.

Tensions in sharing client confidences while respecting autonomy: implications for interprofessional practice

This article aims to explore the ethical issues arising from the sharing of information in the context of interprofessional collaboration. The increased emphasis on interprofessional working has highlighted the need for greater collaboration and sharing of client information. Through the medium of a case study, we identify a number of tensions that arise from collaborative relationships, which are not conducive to supporting interprofessional working in an ethically sound manner. Within this article, it is argued that the way forward within these collaborative relationships is to set clear parameters to the professional-client relationship, paying full regard to the autonomy of both the clients and the professionals involved. We conclude that this approach to working will place the client at the centre of care provision and arguments used for not collaborating that are based on breaches of confidentiality will be negated. Using the approach offered, collaborative working will be not only possible but desirable.

Shared learning for primary health care teams: a success story

This paper sets out an educational model for shared learning for professionals working in primary health care teams (PHCTs). It presents an outline of an experiential educational programme using a simulated learning exercise based on a genogram. Multidisciplinary programmes are inherently problematic and tend to be ad hoc in their choice of educational theory. It was therefore our intention to discover the educational principles and theory that underpinned our innovative educational experience and to offer some fundamental criteria for the planning of future shared learning sessions in PHCTs. The process chosen to make the theory explicit was, 'reflecting on a critical incident' (Reed & Proctor 1993, Tripp 1993).

Effect of eight weeks of treatment with salmeterol on bronchoalveolar lavage inflammatory indices in asthmatics

Using BAL, we studied the effects of 8 wk of treatment with salmeterol on airway inflammation in nine asthmatic subjects in a double-blind crossover placebo-controlled protocol. The study patients were all receiving regular inhaled corticosteroid therapy (400 to 1,000 micrograms beclomethasone dipropionate per day) and inhaled albuterol for symptomatic relief, i.e., subjects who might be considered suitable for treatment with salmeterol. The asthmatic group had significant differences in numbers of epithelial cells and eosinophils in BAL compared with a group of 15 normal control subjects (p < 0.01). During salmeterol treatment mean morning and evening peak flow rates were increased (p < 0.05). There was no significant change in BAL cell profile and no change in percentages of CD4 and CD8 lymphocytes or proportion of lymphocytes expressing HLA-DR after salmeterol. In conclusion, we were unable to demonstrate any significant anti-inflammatory effect of regular salmeterol therapy on airway inflammation using BAL in these asthmatic patients. At the same time, there was equally no evidence of a deterioration in the underlying inflammatory disease process.

Dementia in acute units: the issues

To coincide with World Alzheimer's Day, Nursing Standard this week launches a major new series which looks in detail at one of the most pressing nursing problems of the age--coping with the behaviours of people with dementia who are admitted to acute care units. The series, which consists of seven articles, presented at monthly intervals, takes a very practical look at how nurses in such units can cope with patients who display behaviours such as wandering, aggression, sexual disinhibition and agitation--behaviours which nurses have difficulty understanding and managing.(ABSTRACT TRUNCATED AT 250 WORDS)

Pleuropulmonary abnormalities in primary Sjögren's syndrome

Sixteen patients with primary Sjögren's syndrome (1 degree SS) who complained of dyspnea were investigated with high resolution computerized tomography of the thorax, bronchoalveolar lavage, and transbronchial biopsy. Six patients had evidence of interstitial fibrosis, 5 had a peribronchiolar lymphocytic infiltration and 3 had pleural thickening. We conclude that significant pulmonary disease is not uncommon in patients with 1 degree SS.

Insulin-like growth factor expression in breast cancer epithelium and stroma

The insulin-like growth factors (IGFs) are mitogens for many cancer cell types. In breast cancer cells, IGF-I and IGF-II have both been shown to stimulate cell proliferation. However, IGF-I mRNA has not been found in human breast cancer cell lines, making it unlikely that IGF-I is commonly expressed as an autocrine growth factor for breast cancer cells. Nevertheless, IGF-I mRNA can be detected in breast cancer tissue samples, and in situ hybridization studies have shown that the message originates from the stromal cells adjacent to normal lobules. IGF-II, on the other hand, has been detected in some breast cancer cell lines. In the estrogen receptor positive cell line T47-D, IGF-II mRNA was induced by estradiol. Furthermore, transfection of an IGF-II expression vector into a previously estrogen-dependent cell line resulted in hormone independent growth. Thus, IGF-II can be expressed as an autocrine growth factor in some breast cancers and its expression may, in part, result in hormone independence. Finally, stromal cells obtained from breast tissues showed that IGF-I was commonly expressed in fibroblasts derived from non-malignant biopsy specimens, while IGF-II mRNA was detected in fibroblasts adjacent to malignant tissue. These studies suggest that IGF-II expression may be important in both autocrine and paracrine regulation of breast cancer cell growth.

Low-dose combination therapy of DUP-785 and RS-61443 prolongs cardiac allograft survival in rats

The introduction of cyclosporine into the immunosuppressive armamentarium has revolutionized transplant surgery with significant improvements in graft survival. The apparent lack of effect of cyclosporine on humoral rejection mechanisms makes the search for other immunosuppressive agents desirable. Two anti-metabolites affecting nucleotide synthesis via different pathways have recently been evaluated for their immunosuppressive potential. DUP-785 (DUP), also known as brequinar sodium, reversibly inhibits de novo pyrimidine synthesis by blocking dihydro-orotate dehydrogenase, thus resulting in the deletion of critical precursors for RNA and DNA synthesis. RS-61443, a morpholinoethyl ester of mycophenolic acid, reversibly and non-competitively blocks inosin monophosphate dehydrogenase, the key enzyme in purine de novo synthesis. A possible additive effect of both drugs was investigated in the rat heart allograft model.

Molecular cloning and primary structure of human glial fibrillary acidic protein

Glial fibrillary acidic protein (GFAP) is an intermediate-filament (IF) protein that is highly specific for cells of astroglial lineage, although its tissue-specific role is speculative. Determination of the primary structure of this protein should be of importance for understanding the functional role it plays in astroglia. Therefore, we isolated a cDNA clone encoding this protein and determined its nucleotide sequence. The predicted amino acid sequence indicates that GFAP shares structural similarities--particularly in the central rod domain and to a lesser degree in the carboxyl-terminal domain--with other IF proteins found in nonepithelial cell types. Considerable sequence divergence in the amino-terminal region of GFAP suggests that the tissue-specific functions of this IF protein might be mediated through this region of the molecule. In contrast, conservation of structural characteristics and a moderate degree of sequence conservation in the carboxyl-terminal region suggest functional similarities. Blot hybridization analysis using the GFAP cDNA as a probe failed to detect GFAP mRNA in both normal and neoplastic human tissues in which IF proteins other than GFAP are known to be expressed.

Molecular cloning and primary structure of human chromogranin A (secretory protein I) cDNA

Chromogranin A (CGA), also referred to as secretory protein I, is an acidic protein that has been detected in all neuroendocrine cell types examined and is often present in large amounts relative to other secreted proteins. For example, CGA comprises at least 40% of the soluble protein of the adrenal chromaffin granule, and it appears to be the major secretory protein in the parathyroid secretory granules. CGA complementary DNAs (cDNAs) from bovine adrenal and pituitary have recently been cloned and sequenced and found to be nearly identical. A region of bovine CGA has a high degree of amino acid sequence identity to pancreastatin, a recently isolated porcine peptide that inhibits glucose-induced insulin secretion. This suggests that CGA may be a prohormone. We have cloned and sequenced a human cDNA encoding CGA. This human CGA cDNA has an overall 86% nucleic acid identity to the bovine cDNA. Like the bovine CGA cDNA, the human cDNA has little homology to pancreastatin at the 5' region of this peptide but significant amino acid homology to the carboxyl-terminal portion of pancreastatin where the biologic activity resides. There is an area within the pancreastatin region of human CGA and porcine pancreastatin with a 70% amino acid identity to the calcium-binding moiety of the E-F hand proteins such as parvalbumin and oncomodulin. These data suggest that CGA and pancreastatin may both be members of a larger family of calcium-binding proteins.

Use of a low-power nerve stimulator during sciatic nerve block

The use of a low-power nerve stimulator to aid nerve location during the performance of sciatic nerve block was compared with a conventional anatomically based technique. The success rate, both in terms of the production of an effective block and the duration of postoperative analgesia, was significantly higher in the stimulator groups than in the non-stimulator groups. The implications of the study for both clinical and teaching practice are discussed.

Observations on the feeding and reproductive status of captive feather-tailed possums, Distoechurus pennatus (Marsupialia: Burramyidae)

NA