This allowed detection of minimum odds ratio of 2.2.
The sample size used in this study has a power >80% for the detection of allelic odds ratios >1.5 at a significance level of 0.05.
The goal was to enroll 100 case-patients matched with three controls each, which, if one assumes an α of 0.05 and 80% power, would allow detection of an odds ratio of >2.3 for exposures observed in 15% of controls.
The size of the study will enable detection of minimum odds ratios of 1.3, 1.4 and 1.7 for exposure whose prevalence in controls are 30, 10 and 5percentt, respectively, with a power of 80percentt, a type-I error of 5percentt and a number of 1000 cases and 1000 controls.
If hospitalisation rates are lower at 1% and symptoms less prevalent at 10%, a sample of 2,390 will allow detection of an odds ratio of 4.5 for associated signs and symptoms (assuming the outcome is hospitalisation and the exposure is the presence of a given clinical characteristic).
With a 5% two-sided significance level and 80% power, assuming a hospitalisation rate of 2% [ 29, 30] and an individual clinical characteristic prevalence of 25% [ 29], a sample of 2,588 will allow detection of an odds ratio (OR) of 2.4 of associated signs and symptoms (ORs of between 2.5 and 5 have been observed previously [ 29, 31]).
The calculated sample size of 411 donors (137 cases and 274 controls) allowed detection of a 2.0 odds ratio (OR), with an 80% power at a 0.05 significance level (two tailed), and an exposure prevalence ranging from 15 to 50%.
Even more, contrary to other studies, frequent alcohol consumption (4 times and over/week) was not significantly associated with hypertension but misclassification bias could hinder detection of an elevated odds ratio in the highest category of alcohol consumption.
Abbreviations: β beta coefficient, CI confidence interval, LOD limit of detection, OR odds ratio.
PBB: polybrominated biphenyl; PCB: polychlorinated biphenyl; BMI: body mass index; μg/L: microgram per liter; LOD: limit of detection; OR: odds ratio; CI: confidence interval; AOR: adjusted odds ratio.
