Dealing with misclassification and missing data when estimating prevalence and incidence of caries experience.

OBJECTIVES: The aim of this research was to estimate the prevalence and incidence of caries experience (CE) in first permanent molars while dealing with misclassification and missing of data. METHODS: CE was modeled as a Hidden Markov Model in which the response variable is subject to misclassification and missingness. The proposed analysis extends that of García-Zattera et al. (Stat Med 2010;29:3103) by allowing for various patterns of missing data. Findings were illustrated using data from the Signal Tandmobiel study that is a longitudinal oral health intervention study. RESULTS: Differences in the parameter estimates were noted between models that take into account misclassification and missing data and those that do not. Unbiased parameter estimates of prevalence and incidence were obtained without the use of validation data. Models that include subjects with missing data have smaller standard deviations than models that do not. CONCLUSIONS: It is important to account for misclassification to obtain less biased estimates of prevalence and incidence. For a proper estimation of prevalence and incidence in a longitudinal study subject to misclassification, validation data are not needed but when internal they can increase the efficiency in estimating the model. Also, including subjects with missing data increases the efficiency of estimating the parameters.

[Impact of respiratory distress syndrome in very low birth weight infants: a multicenter South-American study]. / Impacto del síndrome de dificultad respiratoria en recién nacidos de muy bajo peso de nacimiento: estudio multicéntrico sudamericano.

OBJECTIVE: To analyze the incidence, risk factors, major morbidity, mortality and resource employment in very low birth weight infants (< 1500 g) with respiratory distress syndrome (RDS). METHODS: Descriptive study using prospectively obtained on-line information from a data base of 20 units belonging to the South American Neocosur Network. A total of 5991 VLBW infants were registered during years 2002-2007. RESULTS: The mean gestacional age was 29.1 weeks (95% CI 29.06-29.21) and the mean of birth weight was 1100.5 g (95% CI 1093.79-1107.37). The global incidence of RDS was 74% (95% CI 73-75). Antenatal steroids were administered to 73% of this population. The main risk factor was lower gestational age (p< 0.001); where as prenatal steroids (OR: 0.59; 95% CI 0.49-0.72), female gender (OR: 0.77; 95% CI 0.67-0.89) and premature rupture of membranes (OR: 0.81; 95% CI 0.68-0.96) were protective factors. Antenatal steroids was also associated with a decrease in mortality in those infants that presented with RDS (OR: 0.40; 95% CI 0.34-0.47). Use of resources was higher in the group with RDS, with a greater use of surfactant (74.3% vs. 7.3%, p< 0.001), mechanical ventilation (82.1% vs. 23.8%, p< 0.001), and more days of oxygen (median of 8 vs. 1 day, p< 0.001) and hospitalization (median of 61 vs. 45 days, p< 0.001). RDS was associated to an increase risk in the incidence of ROP, PDA, late onset sepsis, severe IVH and oxygen requirement at 36 weeks of corrected gestational age. CONCLUSIONS: RDS had a high incidence in very low birth weight infants, despite the frequent use of antenatal steroids. VLBW Infants with RDS had a higher mortality and an increase risk of relevant morbidity. RDS also increased use of resources.