Assumptions when Analyzing Randomized Experiments with Noncompliance and Missing Outcomes

Randomized trials often suffer from a number of complications, notably noncompliance with assigned treatment and missing outcomes. In this paper, basic complications and associated assumptions are catalogued and discussed. Both noncompliance and missing outcomes are posttreatment variables, and therefore adjusting for noncompliance or missing outcomes requires careful analysis. The approach we follow differs from that based on standard structural econometrics models where non intuitive distributional and statistical assumptions are usually introduced to identify parameters of interest from observed data. The assumptions we discuss are instead scientific and foster understanding of how identification from observed data is achieved, regardless of the approach used for inference. We illustrate such assumptions in the case of compliance behavior, assumed to be dichotomous (all or none), and response behavior, also assumed to be dichotomous (respondent or nonrespondent). Starting from simple examples, we review and propose different sets of exclusion restrictions, which limit the number of potential outcomes, and discuss which assumptions seem to be more appropriate for different settings. An important lesson is that there are no universally appropriate assumptions. Different scientific settings support different assumptions as appropriate.     

Prevalence of Infections After In-Office Hysteroscopy in Premenopausal and Postmenopausal Women

Study Objective

To estimate the incidence of infection after diagnostic and operative hysteroscopic procedures performed in an in-office setting with different distension media (saline solution or CO₂).

Chronic subdural hematoma: results of a homogeneous series of 159 patients operated on by residents

AIMS: A series of cases with chronic subdural hematoma operated upon by residents in neurosurgery is analysed. MATERIALS AND METHODS: 159 patients treated between 1998 and 2001 were included in the study. Mean age was 76.4 years and male/female ratio was 1.7/1. The patients were classified both on admission and at discharge according to the Markwalder scale. The standard operative procedure consisted of an enlarged single burr-hole, rinsing the subdural space with iso-osmotic saline solution and insertion of a subdural drain. CONCLUSION: In CSDH, operation by the residents is safe and the results are comparable to those of the major series of the literature as the surgical procedure is standardized.     

Peripheral T-cell lymphomas expressing CD30 and CD15

Coexpression of CD30 and CD15 is typically associated with classic Hodgkin's lymphoma (HL). Peripheral T-cell lymphomas (PTCLs) can often display histologic features that simulate classic HL. However, reports of PTCLs coexpressing both CD30 and CD15 have been infrequently described. We report 11 cases of PTCL in which at least a subset of the neoplastic cells coexpressed CD30 and CD15. The patients included 4 women and 7 men and age ranged from 43 to 83 years (median, 62 years). Nine of 10 patients had advanced stage III or IV disease at presentation. Nodal involvement predominated in 8 of 11 patients, whereas 2 patients presented primarily with skin involvement. Two distinct groups were identified based on morphologic and immunophenotypic features. The first group of 5 cases had histologic features mimicking classic HL with CD30+, CD15+ Reed-Sternberg (RS)-like cells in an inflammatory background of varied extent and composition. The background lymphoid cells showed minimal cytologic atypia. The RS-like cells were negative for CD20 and CD79a in all cases, and CD45 expression was absent in 4 of 5 cases. The RS-like cells expressed CD25 and at least one T-cell-associated marker in all cases. The background T-cell population showed convincing subset predominance in 4 of 5 cases and loss of T-cell-associated antigens in 3 of 5 cases and coexpression of CD30 and CD15 in one case. The second group of 6 cases had morphologic features more in keeping with PTCL than classic HL. The proportion of neoplastic cells coexpressing CD30 and CD15 varied. Loss of T-cell antigens was noted in all cases and CD4 predominated in 4 of 5 cases. Three of the 6 cases expressed CD45. PCR analysis revealed clonal T-cell receptor gamma (TCR-gamma) chain gene rearrangements in 9 of 11 cases, but no immunoglobulin heavy (IgH) chain gene rearrangements. In situ hybridization studies for Epstein-Barr virus were negative in all cases. In some PTCL cases, the overlap with classic HL can be striking, and combined immunophenotypic and molecular studies are often necessary to confirm the diagnosis.     

Choline increases endogenous GABA release in rat hippocampus by a mechanism sensitive to hemicholinium-3

Summary The effects of choline (Ch) on the spontaneous release of endogenous 7-aminobutyric acid (GABA) and of ³H-GABA were studied in superfused rat hippocampal synaptosomes. Choline enhanced in a concentration-dependent way the release of endogenous GABA but did not affect that of the radioactive aminoacid. The effect of Ch was not antagonized by atropine or mecamylamine; moreover, it was not mimicked by acetylcholine, oxotremorine or carbachol. The Ch-induced GABA release was counteracted by hemicholinium-3. Thus the release of endogenously synthesized GABA (but not that of the aminoacid taken up) may be regulated by Ch through a mechanism involving penetration into the releasing terminal through a Ch uptake system. Send offprint requests to M. Raiteri     

Acquired Acral Lipodystrophy in a 6-Year-Old Girl

Abstract:  We report a case of partial lipodystrophy in a 6-year-old girl with normal lipid and glucose metabolism and no family history for similar disorders. The clinical presentation, the laboratory investigations and the natural history in our patient do not match the diagnostic criteria for any of the established lipodystrophy subsets.     

Increased free malondialdehyde concentrations in smokers normalise with a mixed fruit and vegetable juice concentrate: a pilot study.

Background: Cigarette smoking, a cardiovascular risk factor leading to oxygen free radical formation, is involved in the development of serious pathological conditions. On the other hand, a healthy diet and adequate supplementation can help prevent many diseases. The aim of our study was to evaluate in healthy light smokers the effects of supplementation with mixed fruit and vegetable juice powder concentrate on homocysteine metabolism and oxidative status. Methods: In this pilot study, 32 healthy volunteers, 16 light smokers and 16 non-smokers, on twice daily supplementation were monitored at time zero and after 30 days. Plasma homocysteine, and serum vitamin B(12) and folate concentrations were measured by immunoenzymatic assays; reactive oxygen species, total antioxidant capacity and thiol groups by spectrophotometric methods; and total and free malondialdehyde concentrations by gas chromatography-mass spectrometry with isotopic dilution. Results: Baseline free malondialdehyde concentrations were significantly higher in smokers than in non-smokers and normalised after 30-day supplementation. Baseline results for all the other parameters remained unchanged after supplementation, with no significant differences between smokers and non-smokers. Conclusion: This is the first study showing a significant decrease in free malondialdehyde levels in light smokers after 1-month phytonutrient supplementation.