A multi-disciplinary team in the US formulates a hypothesis that links intimate partner violence (IPV) during pregnancy and damage to the fetal brain. They define the outcome of interest as the presence of abnormal findings including blood clot in the fetal brain detected by ultrasound during pregnancy. All infants included in the study later undergo neurological examination after birth to confirm prenatal (before birth) ultrasound observations. To determine whether a woman was actually a victim of intimate partner violence, the investigators used a questionnaire. Respondents were initially asked whether they had ever experienced any violence from their spouse. Based on more detailed questions the violence experienced was categorized into the following subtypes:
The questionnaire was originally validated and found to capture 4 of every 5 cases of true IPV in a random sample comprising 500 pregnant women.
The US investigators proceeded with their longitudinal study and enrolled 300 pregnant women among whom 30% screened positive on ultrasound. Of the total 150 pregnant women with negative history of IPV, 30 had abnormal fetal brain ultrasound findings. Using odds ratio, calculate the association between IPV during pregnancy and intra-uterine fetal brain damage.
5.Now with your new true 2-by-2 table without misclassification of IPV, calculate the association between IPV during pregnancy and intra-uterine fetal brain damage (use the OR as your measure of association)
6. Now with your new true 2 by 2 table without misclassification of IPV, is IPV during pregnancy associated with fetal brain damage?
7. What is the effect of disease misclassification on the odds ratio?