Magnetic bioassay is becoming of great interest in several application including magnetic separation, drug delivery, hyperthermia treatments, magnetic resonance imaging (MRI) and magnetic labelling. The latter can be used to localize bio-entities (e.g. cancer tissues) by using magnetic markers and high sensitive detectors. To this aim SQUIDs can be adopted, however this result in a quite sophisticated and complex method involving high cost and complex set-up. In this paper, the possibility to adopt RTD fluxgate magnetometers as alternative low cost solution to perform magnetic bio-sensing is investigated. Some experimental results are shown that encourage to pursue this approach in order to obtain simple devices that can detect a certain number of magnetic particles accumulated onto a small surface such to be useful for diagnosis purposes.