摘要： In previous work, the performance of a compact and cost-effective point-of-care (PoC) device based on the increase relative optical power (IROP) methodology is reported and it is determined the enhancement in comparison with standard high-resolution spectrometry in terms of limit of detection. This paper describes a new label-free IROP-based biomedical device capable of working with low concentration of reagents and low sample volume per measurement in order to be used for screening different steps necessary in immunoassay optimization. This new approach significantly improves the sensing performance in terms of read-out signal (ΔIROP) per nanometer of biofilm in comparison with our previous work. This improvement is achieved due to the implementation of a laser as light source of the optical read-out system and the redesign of Fabry–Perot transducers by optimizing their reflectivity response and reducing their sensing area. For demonstrating the screening capability of this new PoC device in several immunoassays steps and methodologies, a C-reactive protein detection assay was carried out as a potential application and assay model. It is remarkable that only 10 μL of sample was used per measurement. This label-free IROP-based device complies an easy-to-use and cost-effective tool for immunoassays optimization in terms of performance, reagents cost, and measuring time.