I agree it should not be taken as definitive. However, I do think it makes sense to have done this first, since it provides a relatively quick and low-cost way

I agree it should not be taken as definitive. However, I do think it makes sense to have done this first, since it provides a relatively quick and low-cost way of finding out if there is anything that justifies a more expensive and time-consuming investigation (that yes, should involve a test of toxoplasmosis antibodies). It appears that the answer is yes, it justifies such a study.