Growth curves of "normal" serum total IgE levels throughout childhood: A quantile analysis in a birth cohort.

BACKGROUND: Previous studies of serum total IgE (t-IgE) were not able to discriminate well-enough atopic from non-atopic subjects, that is, with or without serum-specific IgE antibodies to allergens. OBJECTIVES: To model growth curves of the total IgE levels in children without atopic sensitization (hereafter defined as "normal" t-IgE levels) and to test their usefulness in predicting atopic sensitization. METHODS: The German Multicentre Allergy Study (MAS), a birth cohort with 1314 recruited newborns, began in 1990 and examined the participants until age 20 years. Total and specific IgE (t-IgE, s-IgE) were analyzed with a fluorescent enzyme immunoassay ImmunoCAP (TFS, Sweden) at ages 1, 2, 3, 5, 6, 7, 10, 13, and 20 years. Participants were classified as "never atopic" if all their available serum samples had negative response (cutoff: <0.35 kUA /L) for s-IgE to the nine common foodborne and airborne allergenic extracts (milk, egg, soy, wheat, house dust mite, cat, dog, birch, and grass) tested in the MAS birth cohort. By contrast, participants were defined as atopic if they had, for at least at one available serum sample, s-IgE≥0.35 kUA /L to at least one allergenic extract tested. The evolution of t-IgE levels in the "never atopic" children was described by growth curves, estimated by exploiting a quantile regression model. A "reference" percentile, based on the t-IgE value measured at age 5 years, was assigned to each child with no IgE sensitization at that age. Upward deviations from the own "reference" quantile of t-IgE in atopic and "never atopic" children were calculated and a ROC analysis was used to identify the best cutoff point for predicting atopic sensitization. RESULTS: Overall, 1113 of 1314 children were included in this analysis. Of these, 469 were "never atopic" and 644 atopic. Quantile trajectories of t-IgE levels in "never atopic" subjects were stable from 5 years of age, increased to a plateau at age 10-13 years, and decreased slightly afterward. The onset of atopic s-IgE responses was characterized by an upward deviation of serum t-IgE levels from their "reference" trajectory. T-IgE quantiles predicted the onset of atopy with high efficiency (AUC>80%). ROC analysis showed that deviations from the t-IgE level "reference" quantile above 0.32, 0.41, 0.42, 0.30, and 0.58 kU/L (log-units) at 6, 7, 10, 13, and 20 years of age, respectively, predicted an atopic sensitization. CONCLUSION: The growth curves of "normal" serum t-IgE concentrations were estimated in "never atopic" children; for each individual who was non-atopic at 5 years of age a "reference" quantile was identified that represented the individual's "normal" level of t-IgE production. Upward deviations of observed t-IgE levels from the own "reference" quantile, from 6 to 20 years of age, predicted at each year the occurrence of atopic sensitization. CLINICAL IMPLICATIONS: The trajectory of t-IgE levels can be elaborated since age 5 years in non-atopic children. A child whose t-IgE levels are consistently higher than those predicted by his/her growth curve may have developed atopic sensitization.

Skeletal features in patient affected by maxillary canine impaction.

OBJECTIVE: To analyze the skeletal features of patients with maxillary canine impaction. MATERIAL AND METHODS: The complete pre-treatment records of 1674 orthodontic patients were examined. From the subjects with maxillary impacted canine 12 patients were excluded , remaining 108. The subjects with maxillary impacted canine were divided into two study groups: a palatally displaced canine group (PDCG) (77 patients) and a buccally displaced canine group (BDCG) (31 patients). The values of the skeletal features measured on the lateral cephalometric radiograph were compared with a control group (CG) of 121 subjects randomly selected from the initial sample without maxillary canine impaction. The statistical analysis of the difference between the study groups and the CG was tested using χ(2) test and Fisher's exact test. The level of significance was set at P ≤ 0.05. RESULTS: The CG was characterized by increased values of sella- nasion- A point angle (ANB) and by a retro-positioned or smaller lower jaw. PDCG patients showed normal skeletal features compared to the CG, presenting mainly I class and lower rank of II and III sagittal skeletal features. PDCG subjects presented also normal values of the Steiner vertical skeletal relationship angles with normal facial divergence compared to the CG. PDCG cases were also characterized by horizontal and prognathic growth. BDCG did not present significant differences in skeletal features compared to the CG, except for an increased ANB. CONCLUSIONS: Palatally displaced canine (PDC) was frequently the only orthodontic problem of patients and was not associated whit altered skeletal features. The frequent absence of malocclusion in PDC patients explains the delayed identification of this problem. BDCG patients did not present significant differences in skeletal features with respect to the orthodontic population (CG). The presence of both buccally displaced canine (BDC) and malocclusion makes the patient with BDC both aware of the need for, and motivated to undergo, orthodontic treatment.

Finite mixture models for mapping spatially dependent disease counts.

A vast literature has recently been concerned with the analysis of variation in disease counts recorded across geographical areas with the aim of detecting clusters of regions with homogeneous behavior. Most of the proposed modeling approaches have been discussed for the univariate case and only very recently spatial models have been extended to predict more than one outcome simultaneously. In this paper we extend the standard finite mixture models to the analysis of multiple, spatially correlated, counts. Dependence among outcomes is modeled using a set of correlated random effects and estimation is carried out by numerical integration through an EM algorithm without assuming any specific parametric distribution for the random effects. The spatial structure is captured by the use of a Gibbs representation for the prior probabilities of component membership through a Strauss-like model. The proposed model is illustrated using real data.

ROOTCLUS: Searching for "ROOT CLUSters" in Three-Way Proximity Data.

In the context of three-way proximity data, an INDCLUS-type model is presented to address the issue of subject heterogeneity regarding the perception of object pairwise similarity. A model, termed ROOTCLUS, is presented that allows for the detection of a subset of objects whose similarities are described in terms of non-overlapping clusters (ROOT CLUSters) common across all subjects. For the other objects, Individual partitions, which are subject specific, are allowed where clusters are linked one-to-one to the Root clusters. A sound ALS-type algorithm to fit the model to data is presented. The novel method is evaluated in an extensive simulation study and illustrated with empirical data sets.

GINDCLUS: Generalized INDCLUS with External Information.

A Generalized INDCLUS model, termed GINDCLUS, is presented for clustering three-way two-mode proximity data. In order to account for the heterogeneity of the data, both a partition of the subjects into homogeneous classes and a covering of the objects into groups are simultaneously determined. Furthermore, the availability of information which is external to the three-way data is exploited to better account for such heterogeneity: the weights of both classifications are linearly linked to external variables allowing for the identification of meaningful classes of subjects and groups of objects. The model is fitted in a least-squares framework, and an efficient Alternating Least-Squares algorithm is provided. An extensive simulation study and an application on benchmark data are also presented.

Dental anomalies and clinical features in patients with maxillary canine impaction.

OBJECTIVE: To analyze the prevalence, distribution, clinical features, and relationship with dental anomalies of maxillary canine impaction. MATERIALS AND METHODS: The complete pretreatment records of 1674 orthodontic patients were examined. Subjects with maxillary impacted canines were divided into two study groups: a palatally displaced canine (PDC) group (114 patients) and a buccally displaced canine (BDC) group (37 patients). These were compared to a control group of 151 patients who were randomly selected from the initial sample without maxillary canine impaction. The significance of associations between canine impaction and dental and clinical features and anomalies was examined with the chi-square test. RESULTS: PDC patients presented with normal overjet and facial profile and a lower degree of dental arch crowding in comparison to the control patients. PDC patients showed a higher prevalence of impaction of other teeth, dental aplasia, transposition, and peg-shaped maxillary lateral incisors (odds ratios 3.3, 2.6, 8.3, and 5.8, respectively). CONCLUSION: PDC was frequently the only orthodontic problem of patients. BDC group patients did not present with notable differences in clinical and dental features or dental anomalies compared to control subjects.