Comment on “Epilepsy and seropositivity rates of Toxocara canis and Toxoplasma gondii”

We have read with great interest the paper from Akyol et al. looking for the link between Toxocara or Toxoplasma seropositivity and epilepsy. On the basis of their findings, the authors concluded that they did not find any association between epilepsy and Toxoplasma gondii and Toxocara canis seropositivity. To date only a few studies have been carried out on this issue and, from this point of view, further evidence should be helpful. However we have some concerns on key methodological aspects. Themost important limitation in the interpretation of thepresentedresults is that,dueto thesmall sample size, the power of this study was low to detect a difference between cases and controls (type II error). Based on theexposure proportions found in the study, thepower estimateswere only 39.7% forT. gondii and 17.8% for T. canis to detect an odds ratio of 2 (with an alpha risk of 5%). It is not really surprising then that the authors did not statistically confirm the difference they found (crude odds ratio = 2.14 forT. canis). Moreover, besides the lack of a precise definition of epilepsy, the authors reported a higher frequency of generalized epilepsies, as expected, because of the inclusion of only cryptogenic (in the abstract) or idiopathic (in themethods)epilepsies. Someof themcould have a genetic background while, according to previous data, a stronger associationwas foundwith focal epilepsies, and seems biologically more plausible. Finally, we would like to stress that in a case— control study, the composition of the control group is crucial. In this study, it is composed of volunteers, and the students are significantly more frequent in