An "Anti-Neuronal Ab / Full Panel: Anti-Hu, RI, YO" test is a blood test that checks for the presence of three specific antibodies - anti-Hu, anti-Ri, and anti-Yo - which are considered markers for a group of neurological disorders known as paraneoplastic syndromes, often associated with underlying cancers like small cell lung cancer, breast cancer, and ovarian cancer; essentially, it's a comprehensive screening for these antibodies to identify potential paraneoplastic neurological conditions.