The use of logistic discrimination and receiver operating characteristics (ROC) analysis in dentistry

Logistic regression is a statistical method which allows an investigator to 'explain' or 'predict' a binary response variable from a set of independent variables. In particular, it may be used to classify persons for example, as diseased or healthy, high risk or low risk etc. (logistic discrimination). During recent years this method has been of increasing interest and importance in dentistry. Since this demanding statistical method may not be easily accessible to dentists, a description is provided of its basic characteristics in an introductory and condensed form. A worked example, 'identification of children with high caries risk', is presented in order to demonstrate the application and use of the method. Following the presentation of the logistic model, evaluation of the performance of a classification model by means of 'receiver operating characteristic (ROC) analysis' is demonstrated. The presentation of these statistical tools here, puts more weight on verbal explanation and on graphical representations than on mathematical details. This statistical tools here, puts more weight on verbal explanation and on graphical representations than on mathematical details. This may help to make the methods accessible to readers who have insufficient time to study a more comprehensive discourse.

Caries prevalence in Switzerland

The first Swiss studies of DMFT counts were undertaken in the late 1950s and showed values of 7.7-11.3 for children of 12 years of age and 12.6-18.6 for children of 15 years of age. Although these studies did not use current statistical sampling methods, and so are not directly comparable, the results of the most recent surveys do present a startling contrast. In 1992, DMFT figures had fallen to an average of 1.12 and 2.22 DMFT in 12- and 15-year-olds respectively. Reasons for these sharp declines are discussed, as are the available figures for adults over the same period of time. Predictions are made for DMFT levels for the year 2008 and their likely impact on dental services.

Erythropoietin receptor mRNA expression in human endothelial cells

A previous report demonstrated that endothelial cells have erythropoietin receptors and respond to this hormone with enhanced proliferation. The present study demonstrates the existence of mRNA for erythropoietin receptor in human umbilical vein endothelial cells. We have reverse transcribed mRNA of endothelial cells and then used different PCR primers to amplify erythropoietin receptor target cDNA between exons 5 and 6 as well as 3-5 in addition to an internal standard DNA fragment. Correspondence of size as well as location of restriction endonuclease scission (Ava II) was used in comparing the amplified fragments of human endothelial cell erythropoietin receptor to those of two human erythroleukemia cell lines, OCIM1 and K562. No alpha- or gamma-globin mRNA was detected in endothelial cells but was readily demonstrable in OCIM1 cells. In addition, to determine whether the expression of human erythropoietin receptor on endothelial cells occurs in vivo, sections of umbilical cord and placenta were immunostained with antibodies against the extracellular portion of the receptor; the results showed strong positive staining of the vascular endothelium.

Thioallyl compounds: potent inhibitors of cell proliferation

S-Allylmercaptocysteine was shown to inhibit vascular smooth-muscle and umbilical endothelial cell proliferation. Inhibition was dose-dependent and affected smooth-muscle cells more than endothelial cells. S-Allylmercaptocysteine was two orders of magnitude more potent than S-allylcysteine and cells grown in its presence showed distinct changes in their phosphorylation compared to untreated controls. Among the proteins whose phosphorylation was altered were GTP-activating protein, protein tyrosine phosphatase-1B and p34cdc2. We conclude that thioallyl compounds, natural constituents of garlic and known to inhibit malignant cells, can also reduce the proliferation of normal cells.

Atrial natriuretic factor: does it have a role in psychiatry?

Atrial natriuretic factor (ANF) is the first of a group of atrial natriuretic peptides (ANPs) discovered since 1981. This group of peptides is thought to have an important role in sodium homeostasis and regulation of fluid volume. Although the role of ANF in cardiovascular and renal disorders is under investigation, the specific signaling involvement that ANF may have in the central nervous system is still unexplored. To date, ANF has not as yet been associated with a given functional area in the brain, nor has it been shown to be linked to any particular psychopathology. Neuropharmacology research of these peptides and their drug manipulation is needed to advance our knowledge of the possible role of ANF in psychiatry beyond the current level of speculation.

Fluoride varnishes (Duraphat): a meta-analysis

In the present article we analyze a series of studies designed to detect the caries preventive effect of Duraphat by means of meta-analysis. Meta-analysis is a collection of statistical methods designed to investigate and to summarize a series of investigations. It may be a valuable tool to complement traditional narrative reviews. During the last years meta-analysis has attracted increasing interest in sociology, psychology and medicine. In order to find previous studies concerned with the clinical effects of Duraphat we applied a systematic literature search. Papers were included independent of results when they fulfilled a checklist of well defined methodological selection criteria. In order to aggregate the results of the Duraphat-studies we used different complementary statistical approaches: Firstly, the so-called file drawer problem is considered. This may help to get a better insight into the problem of underreporting non-significant results or publication bias. It was found to be very unlikely that underreporting of non-significant results could reverse the conclusion into an overall null-result. After that, the inhomogeneity between studies is investigated. The overall variation of caries reduction R is separated into two components: A between study component of variance and a variance pertaining to the individual studies (random effects model). It was found that the overall variation is dominated by the between studies variation and not by the sampling variation. Due to the pronounced variation between studies the confidence interval of the overall effect size (R = 0.38) is quite large (95%-Cl: 0.19-0.57).(ABSTRACT TRUNCATED AT 250 WORDS)

A note concerning the caries preventive effect of Duraphat

In a previous article (1) we analyzed a series of eight studies concerned with the effect of Duraphat in the prevention of dental caries by means of meta-analysis. A random effects model was used to estimate an overall effect size of caries reduction R and the corresponding confidence interval. In the present short communication we complement this previous study by neglecting the within study variation to the overall variation which is dominated by between study variation. This allows us to include a larger number of studies and thus make fuller use of the available information. We estimate nonparametrical confidence intervals for effect sizes (caries reduction) by means of the "bootstrap method". The overall caries reduction R on permanent teeth (14 studies) was estimated to be: R = 0.38 (95%-CI: 0.25-0.50).

Neural connections of the suprachiasmatic nucleus and medial hypothalamus of the Syrian hamster (Mesocricetus auratus)

The neural connections of brain areas involved in the control of circadian rhythms were investigated in the Syrian hamster by observing the anterograde and retrograde neural labelling resulting from injections of HRP-WGA into the suprachiasmatic nucleus (SCN) and subparaventricular zone (SPZ). The neural connections of these 2 brain areas in the strongly photoperiodic hamster are very similar to those in the more weakly photoperiodic rat. Two differences were observed: (1) in the rat, but not in the hamster, the SCN projects to the ventral geniculate nucleus and intergeniculate leaflet of the thalamus; and (2) reciprocal contralateral neural connections appear to be more numerous in the hamster than in the rat SCN. These differences may relate to the differences in photoperiodic sensitivity of the 2 species.

The impact of lubricants on latex condoms during vaginal intercourse

The objective was to evaluate the impact of additional lubricant on condom breakage and slippage. Two hundred and sixty-eight couples used 6 new and 6 aged condoms during vaginal intercourse and were instructed to use 2 of each type with either water-based lubricant, oil-based lubricant or no additional lubricant. The use of either oil-based or water-based lubricant increased slippage rates of new and aged condoms, although only one pairwise comparison (oil-based lubricant vs. no additional lubricant) was statistically significant (8.5% vs. 3.8%, P = 0.004). The use of oil-based lubricant increased breakage, although not statistically significantly, in both new and aged condoms. Water-based lubricant did not impact the breakage rate of the new condoms and decreased the breakage rate of the aged condoms (no additional lubricant 4.5% vs. water-based lubricant 2.1%, P = 0.029). From a functional perspective, this study suggests that condom users should be told not to use oil-based lubricants. The negative impact of water-based lubricant on slippage may be outweighted by the protective influence on breakage, especially for aged condoms. Over three-quarters of the couples (76%) had at least some incorrect knowledge, according to current condom instructions, of the type of lubricant that should be used with condoms.

Increased Levels of Soluble Adhesion Molecules in Type 2 (Non-Insulin Dependent) Diabetes mellitus Are Independent of Glycaemic Control

Patients with Type 2 (non-insulin dependent) diabetes mellitus are at increased risk of thrombosis and the premature development of atherosclerosis. This may be related to damage to the endothelium (which may be the primary target tissue for the disease process) resulting from a loss of normal glycaemic metabolic control. Thus changes in endothelial cell function, such as modified release of soluble leukocyte and platelet adhesion molecules, may be important. Accordingly, E-selec-tin, von Willebrand factor (vWf), vascular cell adhesion molecule (VCAM) and intercellular adhesion molecule (ICAM) were measured in serum from 60 patients and 76 controls. Raised levels of vWf (p = 0.0002), E-selectin (p <0.0001) and VC AM (p = 0.003) in patient’s samples failed to correlate with glycaemic control as assessed by levels of fructosamine and glycated haemoglobin, or with 24 h urine albumin. Levels of ICAM were not increased in our patients. Levels of the two endothelial cell products, vWf and E-selectin, failed to correlate although E-selectin correlated with low density lipoprotein cholesterol (p = 0.016). vWf correlated with VCAM (p <0.001) and hypertension (p = 0.032). We conclude that levels of soluble adhesion molecules vWf, E-selectin and VCAM are raised in Type 2 diabetes mellitus. The mechanisms for these changes appear to be independent of glycaemic control but may relate to concurrent hypertension and/or hypercholes-terolaemia.

Second primary cancer in irradiated stage I testicular seminoma

The incidence of second primary cancer (SPC) was determined in 64 irradiated stage I testicular seminoma patients, treated and followed at the Northern Israel Oncology Center from 1968 to 1988. Seven (11%) patients developed a total of eight second cancers. The cumulative risk for developing second primary cancer at ten, 15 and 20 years following the diagnosis of seminoma was 2.5%, 5.1% and 8.9%, respectively. Two patients developed SPC within the radiation field (urinary bladder, sigmoid colon) and four patients outside the radiation field (bronchogenic cancer, thymoma, malignant melanoma, thyroid cancer). In two patients, who developed lung cancer and testicular seminoma, respectively, scatter dose from the main radiation field could not be excluded as one of the factors contributing to the SPC. Three patients died as a direct result of their SPC. It is concluded that there is a low, but significant risk of solid SPC among patients apparently cured of early stage seminoma. It will be important in future surveillance studies of stage I seminoma to assess the risk of SPC in the non-irradiated patients.

Neovascularization and the appearance of morphological characteristics of the blood-brain barrier in the embryonic mouse central nervous system

Vascularization and expression of blood-brain barrier (bbb)-associated morphological characteristics during the embryonic development of the mouse central nervous system (CNS) was studied by ultrastructural analysis. At embryonic day 9 (E9) capillaries were only found in the perineural mesenchymal tissue. These capillaries showed fenestrations, and pericyte like cells (PC) were found joined to the vessel walls. Around E10 endothelial cells (EC) together with PC started invading the intraneural section. At this stage, the immigrating endothelial cells lost their fenestrations and exhibited numerous, partly extended junctional complexes, which appeared 'tight' in some places. A first intraneural anastomotic plexus was observed at E10, as evidenced by the presence of blood cells in all capillary lumens. While the number of junctional complexes remained constant in intraneural capillaries, the frequency of pinocytotic vesicles decreased significantly from E10 to E17. These findings indicate that from the first day of intraneural vascularization onwards, the morphological properties of the bbb are present in the early embryonic mouse cerebral cortex.