Characteristics of the subject and interview influencing the test-retest reliability of the Diagnostic Interview for Children and Adolescents-Revised.

This paper reviews some of the characteristics of the informants as well as some of the attributes of the DICA-R interview that could influence the test-retest reliability in a sample of 109 psychiatric outpatients aged 7-17 years. Different regression models using reliability coefficients constructed from the kappa statistic were obtained. Of those characteristics evaluated in the children, a high level of psychological impairment proved to be significant when it came to predicting the lowest test-retest reliability of the answers; none of the subject-related characteristics were significant in the adolescent patient model. The attributes of the questions that proved to be significant when explaining the lower reliability obtained for the individual question in the children's model were the length of the questions (longest questions), the content (internalising), the presence of time concepts, comparison with the peer group, and the need to exercise judgement; in the adolescents' model, the significant attributes were found to be the internalising content, the presence of time concepts, evaluation concerning the impairment caused by the disorder, and the need to exercise judgement. In the group of children our results are in accordance with the original paper. Similar results were found with adolescents. These findings have implications for the development and revision of new interview schedules.

Regression models: calculating the confidence interval of effects in the presence of interactions.

The main goal of regression analysis (multiple, logistic, Cox) is to assess the relationship of one or more exposure variables to a response variable, in the presence of confounding and interaction. The confidence interval for the regression coefficient of the exposure variable, obtained through the use of a computer statistical package, quantify these relationships for models without interaction. Relationships between variables that present interactions are represented by two or more terms, and the corresponding confidence intervals can be calculated 'manually' from the covariance matrix. This paper suggests an easy procedure for obtaining confidence intervals from any statistical package. This procedure is applicable for modifying variables which are continuous as well as categorical.

The influence of nutrient intake on the biochemical parameters of iron status in a healthy paediatric Mediterranean population.

A random sample of 302 children, aged between 6 months and 15 years, of a healthy Mediterranean population were studied. Abnormal values of biochemical parameters of iron status were frequently found. In the 0.5-2 year group, erythrocyte protoporphyrin values were abnormal in 13.5% of subjects, serum ferritin in 9.7%, transferrin saturation capacity in 75.3%, mean red cell volume in 4.1% and haemoglobin in 9.7%. Comparing nutritional intake (24 h dietary recall over 3 days) between individuals at low and high values of biochemical iron status some significant differences were found in each age group but in no case with regard to heme iron intake. In the overall age-adjusted study population, the nutritional intake had a low but significant explanatory capacity of the variance of the measured biochemical iron status parameters (between 1.1% for transferrin saturation capacity and 4.5% for serum ferritin) and a non-significant capacity in those children younger than 3 years. In conclusion, although the dietary pattern in our area favours a good iron bioavailability, in our population the nutritional intake was shown to have a limited relationship with the parameters of biochemical iron status parameters. These data suggest that, in healthy children, abnormal biochemical iron status parameters may be related to factors other than nutritional intake.