From The basis for folinic acid treatment in neuro-psychiatric disorders by Ramaekers et al., 2016, at the very end of the article:
Because the presence of FRα antibodies can show significant serum titer fluctuations, we recommend collection of at least three serum samples at one-week intervals to rule out FRα autoimmune disorder. For the group of patients with major depression, our preliminary results suggest selecting patients with treatment-resistant major depression for FRα autoantibody testing which is estimated to occur at a prevalence of ~56%. However, further studies are needed to confirm our findings and to detect the prevalence of FRα antibodies at baseline among different patient groups suffering from schizophrenia or major depression.
What could be the meaning of this "at baseline"? My guess is that it means "before the beginning of treatment". Is this so?