Abstract: This invention relates primarily to a fluid collection device for laboratory analysis. Accordingly, the fluid collection device (100) includes a specimen collection tube assembly (200); characterised in that the specimen collection tube assembly (200) comprises: a) a barrel (210) defining a first chamber (211); b) an inner tube or plunger (220) defining a second chamber (221). It should be noted that the barrel (210) is provided with a luer tip (214) at one end, and another end (215) is in slidable sealing engagement with the inner tube (220) defining a closed system thereof. The inner tube (220) is provided with a luer tip (224) at one end, and the opposite end is equipped with a seal (222) separating the first and second chambers (211 and 221) in said closed system.