In spite of a current increasing trend in the development of miniaturized, standalone point-of-care (PoC) biosensing platforms in the literature, the actual implementation of such systems in the field is far from being a reality although deeply needed. In the particular case of the population screenings for local or regional diseases related to specific pathogens, the diagnosis of the presence of specific antibodies could drastically modify therapies and even the organization of public policies. The aim of this work was to develop a fast, cost-effective detection method based on the manipulation of functionalized magnetic beads for an efficient diagnosis of hypersensitivity pneumonitis (HP), looking for the presence of anti-pigeon antigen antibodies (APAA) in a patient’s serum. We presented a Diagnostic Biosensor Method (DBM) in detail, with validation by comparison with a traditional high-throughput platform (ELISA assay). We also demonstrated that it was compatible with a microfluidic chip that could be eventually incorporated into a PoC for easy and broad deployment using portable optical detectors. After standardization of the different reaction steps, we constructed and validated a plastic chip that could easily be scaled to high-volume manufacturing in the future. The solution proved comparable to conventional ELISA assays traditionally performed by the clinicians in their laboratory and should be compatible with other antibody detection directly from patient samples.