Is Small Still Beautiful for the Strengths and Difficulties Questionnaire? Novel Findings Using Exploratory Structural Equation Modeling.

During the present decade a large body of research has employed confirmatory factor analysis (CFA) to evaluate the factor structure of the Strengths and Difficulties Questionnaire (SDQ) across multiple languages and cultures. However, because CFA can produce strongly biased estimations when the population cross-loadings differ meaningfully from zero, it may not be the most appropriate framework to model the SDQ responses. With this in mind, the current study sought to assess the factorial structure of the SDQ using the more flexible exploratory structural equation modeling approach. Using a large-scale Spanish sample composed of 67,253 youths aged between 10 and 18 years (M = 14.16, SD = 1.07), the results showed that CFA provided a severely biased and overly optimistic assessment of the underlying structure of the SDQ. In contrast, exploratory structural equation modeling revealed a generally weak factorial structure, including questionable indicators with large cross-loadings, multiple error correlations, and significant wording variance. A subsequent Monte Carlo study showed that sample sizes greater than 4,000 would be needed to adequately recover the SDQ loading structure. The findings from this study prevent recommending the SDQ as a screening tool and suggest caution when interpreting previous results in the literature based on CFA modeling.

Kyphoscoliotic ventilatory insufficiency: effects of long-term intermittent positive-pressure ventilation.

OBJECTIVES: To determine the effects of long-term nocturnal intermittent positive-pressure ventilation (NIPPV) on symptoms, pulmonary function test results, sleep, and respiratory muscle performance in patients with ventilatory insufficiency due to severe kyphoscoliosis. DESIGN: A prospective study in which 16 severe kyphoscoliotic patients were treated with NIPPV delivered by volume-cycled and pressure-cycled ventilators, over a period of 36 months. INTERVENTIONS AND MEASUREMENTS: At baseline, pulmonary function tests, blood gas measurements, polysomnography, and respiratory muscle strength (measured by noninvasive indexes) were obtained. Symptoms and the number of hospitalizations in the previous 6 months also were recorded. Patients then began using a ventilator for > 1 to 2 days, in order to select the type of ventilator and the appropriate interface. Patients returned for evaluation (in outpatient setting) every 6 months for a follow-up period of 3 years. At 6 months, polysomnography was repeated, and by the third year clinical and functional parameters had been reassessed. RESULTS: All symptoms improved significantly with NIPPV therapy, when compared with the baseline values. The mean (+/- SD) PaO(2) and FVC values increased at 36 months compared with baseline values (62.6 +/- 7.1 vs 67.8 +/- 8.8 mm Hg, respectively; and 37.9 +/- 7.2% vs 47.5 +/- 11.9%, respectively; p < 0.05 for both). There were significant improvements in mean maximal inspiratory pressure (55.8 +/- 17.4 to 78.5 +/- 17.5 cm H(2)O), maximal expiratory pressure (53.8 +/- 17.7 to 72.3 +/- 11.0 cm H(2)O), mouth pressure (0.28 +/- 0.08 to 0.22 +/- 0.02 cmH(2)O), and pressure-time index (0.18 +/- 0.05 to 0.11 +/- 0.02; p < 0.05 for all comparisons). There were no significant differences in breathing pattern and ventilatory drive. After 6 months, nocturnal oxyhemoglobin saturation improved, however, there was no significant change in sleep architecture. All patients subjectively perceived a better quality of life after beginning ventilation, which persisted over the course of the study. CONCLUSIONS: Long-term NIPPV therapy improves daytime blood gas levels, respiratory muscle performance, and hypoventilation-based symptoms in patients with severe kyphoscoliosis.