Abstract: Determination of microorganisms in body fluids for diagnosis is carried out by passing a body fluid through a column packed with a sorbent which traps microorganisms contained by the body fluid. A culture medium is added to the column, and after culturing the presence of microorganisms is determined. The column is a substantially cylindrical body and is connected via a porous partition to a conical terminal at each end. One conical terminal is an inlet and the other is an outlet. A sorbent porous material is positioned between the partitions and the partitions have different porosities. Total inner volume of the column is about 30 to 300 ml, and volume ratio of the cylindrical body to the conic terminals is about 1:0.3 to 1:5. Preferably, the volume of the cylindrical body is about 10 to 100 ml and the total volume of the both conic terminals is about 20 to 200 ml.