The importance of parental knowledge in the association between ADHD symptomatology and related domains of impairment

European Child & Adolescent Psychiatry - Parents of children with ADHD experience several difficulties while raising their children and report lower levels of knowledge about their...     

Departure from normality in multivariate normative comparison: The Cramér alternative for Hotelling's T

Crawford and Howell (1998) have pointed out that the common practice of z-score inference on cognitive disability is inappropriate if a patient's performance on a task is compared with relatively few typical control individuals. Appropriate univariate and multivariate statistical tests have been proposed for these studies, but these are only valid if the data are Gaussian (normal) distributed. Previous studies have investigated the consequences for Type I error rates of using the univariate test when data are not Gaussian. In this paper we examine the effects of violation of the Gaussian assumption on nominal Type I error rates for the multivariate test. We also consider a new test that has been devised recently, called Cramér's test, as a viable alternative for the multivariate normative comparison. In simulations we show that the new test not only provides a distribution free alternative for existing methods, but also has the advantage that it is substantially more powerful in most common research settings. We demonstrate the use of the new test with an application to two individuals diagnosed with autism.     

Simultaneous MEG and EEG source analysis

A method is described to derive source and conductivity estimates in a simultaneous MEG and EEG source analysis. In addition the covariance matrix of the estimates is derived. Simulation studies with a concentric spheres model and a more realistic boundary element model indicate that this method has several advantages, even if only a few EEG sensors are added to a MEG configuration. First, a simultaneous analysis profits from the 'preferred' location directions of MEG and EEG. Second, deep sources can be estimated quite accurately, which is an advantage compared to MEG. Third, superficial sources profit from accurate MEG location and from accurate EEG moment. Fourth, the radial source component can be estimated, which is an advantage compared to MEG. Fifth, the conductivities can be estimated. It is shown that conductivity estimation gives a substantial increase in precision, even if the conductivities are not identified appropriately. An illustrative analysis of empirical data supports these findings.     

Major clinical events, signs and severity assessment scores related to actual survival in patients who died from primary biliary cirrhosis. A long-term historical cohort study

BACKGROUND/AIMS: One of the prognostic methods for survival in primary biliary cirrhosis (PBC) is the Mayo model, with a time-scale limited to 7 years. The aim of our study was to assess how major clinical events, signs, several severity assessment methods and Mayo survival probabilities fit in with actual patient survival, by using yearly observations until 0.5 years before patient death from PBC. METHODOLOGY: Data of 32 patients dying from PBC were collected prior to death at -0.5, -1, -2 etc. years (median: -5 years, range: -16 to -0.5 years). Major events registered were: first occurrence of ascites, upper gastrointestinal bleeding or manifest hepatic encephalopathy and signs, first observation of spider naevi or purpura. Severity assessment methods applied (all with scores and classes) were: Mayo (M), Child-Campbell (C), Pugh-Child (P), Pugh-Child-PBC (PP), 'Child-Pugh' (CP), and Ascites Nutritional State-Child (ANS). Fifty percent survival estimates were calculated from Mayo scores. Severity assessment method variables were: ascites (C, P, PP, CP, ANS), encephalopathy (C, P, PP, CP), nutritional state (C, ANS), edema (M), age (M), serum albumin (M, C, P, PP, CP), bilirubin (C, M, P, PP, CP), and prothrombin time (M, P, PP, CP). RESULTS: In 27 out of 32 patients a major event occurred, always between -6 and -0.5 years (median: -1 year) and, never between -16 and -7 years (p < 0.0001). A sign was first observed in 30/32 between -14 and -0.5 years (median: -2 years). Compared to the total population, a sign, and even more so, an event indicated a shorter survival (p = 0.004 and p = 0.0002, respectively). The median 50% estimated survival (predicted by the Mayo model) fitted the actual survival from -6 to -0.5 years (r = -0.7, p < 0.0001), but not from -16 to -7 years (r = -0.1, p = 0.4). All -6 to -0.5-year severity scores correlated (p < 0.0001) both with actual survival (M, C, P, PP, and CP r = 0.7; ANS r = 0.5) and with estimated M 50% survival (C, P, PP, CP r = -0.9; ANS r = -0.6; M score: -0.99), but none with actual survival from -16 to -7 years, except for M, slightly (r = -0.3, p = 0.04). A nomogram for mean C, CP, M and ANS scores related to actual survival was constructed for the -6 to -0.5-year period. The C and CP classes A, B, and C did not appear to distinguish sufficiently into actual survival, whereas the M classes did. CONCLUSIONS: The occurrence of a major event appeared to exclude survival over 6 years. In these final 6 years, Child-Campbell, Mayo and Pugh scores correlated equally well with actual survival and better than Ascites/Nutritional State score. In our PBC patients, Campbell was an excellent alternative for Pugh; for Pugh, the original Child-Turcotte variable limits were fully sufficient.