The present disclosure pertains to a system for separating plasma and/or serum from blood. The system is configured to separate plasma and/or serum from between about 20 and about 50 μl of blood. Separating plasma and/or serum from that amount of blood may be useful during a bilirubin level estimation in newborn babies. The system alleviates the need to centrifuge a sample of blood to separate the blood plasma and/or serum. The system is configured such that the separated serum is held by the system during an optical analysis to estimate bilirubin levels, thus eliminating the need to transfer the serum sample to a cuvette for analysis. In some embodiments, the system comprises a cartridge body, a filter, a serum pathway, an analysis port, a negative pressure source, a suction connector port, and/or other components.
