A low-cost photonic lab on a chip with three different working regimes for cell screening is presented, namely scattering, scattering+absorbance and absorbance. In all regimes, the whole spectral response in absorbance is obtained, being possible to determine for each regime which is the optimal working wavelength that provides the highest performance. Experimental limits of detection (LOD) of 54.9 ± 0.7 cells, 53 ± 1 cells, and 105 ± 4 cells, depending on the working regime used, have been obtained. The system has also been used for measuring the dead/live cell ratio, obtaining LODs between 7.6 ± 0.4% and 6.7 ± 0.3% of dead cells.