Enzyme-linked immunosorbent assays (ELISA) are the most popular immunoassay techniques performed every day in hospitals and laboratories and they are used as a diagnostic tool in medicine and plant pathology, as well as a quality-control check in various industries. However, complex labeling techniques are required to be able to perform the assay and non-specific binding and endpoint timing are difficult to optimize. These issues could be solved by label-free techniques such as silicon nanophotonic microring resonator sensors, but this platform requires complex microfluidics, which is very much removed from the daily practice in e.g. hospital labs, which still relies to a large degree on platforms like 96-well microtiter plates or reaction tubes. To address these issues, here, we propose the combination of a simple and compatible reaction tube platform with label free silicon-on-insulator (SOI) photonic biosensors, where the flow is through the sensor chip as opposed to over the chip as in more conventional approaches. This device allows real time detection and analysis. Its great flexibility and small footprint make it ideal for an easy handling in any laboratory.