A team of neurologists and psychologists researching intellectual function is reviewing the results of a study on the association between childhood lead exposure and adult intellectual function. Which of the following is the best approach to further investigate the association between environmental lead exposure in childhood and adult intellectual function?
A)Additional study is not warranted given nonsignificant results after adjusting for maternal IQ
B)Conduct a new large-scale prospective cohort study
C)Perform stratified analysis based on maternal IQ
D)Pool the data from several studies
E)Reassess the outcome measurement

Question

Quizplus · Accepted Answer

Explanation: Meta-analysis is an epidemiologic tool used to increase the power of a study (ie, its ability to detect associations, if such associations exist) by pooling the data from several studies. When a single study has a very small sample size and the outcome under study is rare, it is difficult for the study to find statistically significant associations even when real and valid associations exist. In such cases, meta-analysis can be used to increase the sample size, thereby increasing the power of the analysis. The major disadvantage of meta-analysis includes concomitant "pooling" of the biases and limitations of individual studies into one analysis. However, the advantages in statistical power and robustness for estimating associations typically outweigh the limitations of this epidemiologic tool. In this case, pooling data from other studies to conduct a meta-analysis is the best approach to increase sample size and achieve adequate statistical power for further investigating the association between environmental lead exposure in childhood and adult intellectual function (IQ), while also adjusting for other potential confounders. (Choice A) Based on the abstract, the study results suggest that lead exposure in childhood predicts IQ in young adulthood. However, researchers concluded that the role of maternal IQ in the association of interest cannot be excluded. Therefore, additional study might be needed to elucidate the effect maternal IQ has on the association under study. (Choice B) Conducting a new large-scale prospective cohort study may seem to be an appropriate next step. However, due to the known effects of lead and the tremendous efforts to eliminate all lead hazards in children, conducting a prospective cohort study at this time will be problematic and potentially ethically challenged. (Choice C) Stratified analysis refers to analyzing subjects based on the presence or absence of a certain variable (eg, maternal IQ); it can be used to control confounding factors. However, the study lacked sufficient statistical power to evaluate the effect of maternal IQ on the association of interest. (Choice E) In this study, lead exposure was measured through standardized blood sample testing at different points in time. Using standardized testing significantly reduced the likelihood of measurement bias in the outcome of the study. Furthermore, reassessing the outcome on this individual study is not feasible given that the risk factor is childhood exposure to lead (past exposure). Educational objective: Meta-analysis is conducted by pooling the data from several studies to increase statistical power.

A Team of Neurologists and Psychologists Researching Intellectual Function Is