A device for quantitatively determining the presence or absence of one or more acute phase protein(s), such as Hepatocyte Growth Factor, in a biological sample from an individual, a presence of one or more acute phase protein(s) in said biological sample being indicative of an acute bacterial infection in said individual, said device comprising a) at least one surface on which a composition comprising: i) a proteoaminoglycan or dextran sulphate and ii) toluidine blue (chemical formula: C 15 H 16 N 3 S) has been immobilized, b) optionally a solid support onto which said at least one surface may be attached, wherein said at least one surface comprises a material suitable for immobilization of said composition comprising proteoaminoglycan or dextran sulphate and toluidine blue; and wherein on at least one surface of a) the ratio of the amount of a proteoaminoglycan or dextran sulphate to the amount of toluidine blue in said composition on said at least one surface is selected from the group of ratios consisting of: • about 100:1, such as about 90:1 to about 110:1 (surface 1); • about 140:1, such as about 135:1 to about 145:1 (surface 2); • about 165:1, such as about 160:1 to about 170:1 (surface 3); • about 180:1, such as about 175:1 to about 185:1 (surface 4); • about 200:1, such as about 190:1 to about 210:1 (surface 5); and • about 225:1, such as about 220:1 to about 230:1 (surface 6). a) at least one surface on which a composition comprising: i) a proteoaminoglycan or dextran sulphate and ii) toluidine blue (chemical formula: C 15 H 16 N 3 S) has been immobilized, i) a proteoaminoglycan or dextran sulphate and ii) toluidine blue (chemical formula: C 15 H 16 N 3 S) has been immobilized, b) optionally a solid support onto which said at least one surface may be attached, wherein said at least one surface comprises a material suitable for immobilization of said composition comprising proteoaminoglycan or dextran sulphate and toluidine blue; and wherein on at least one surface of a) the ratio of the amount of a proteoaminoglycan or dextran sulphate to the amount of toluidine blue in said composition on said at least one surface is selected from the group of ratios consisting of: • about 100:1, such as about 90:1 to about 110:1 (surface 1); • about 140:1, such as about 135:1 to about 145:1 (surface 2); • about 165:1, such as about 160:1 to about 170:1 (surface 3); • about 180:1, such as about 175:1 to about 185:1 (surface 4); • about 200:1, such as about 190:1 to about 210:1 (surface 5); and • about 225:1, such as about 220:1 to about 230:1 (surface 6). wherein said at least one surface comprises a material suitable for immobilization of said composition comprising proteoaminoglycan or dextran sulphate and toluidine blue; and wherein on at least one surface of a) the ratio of the amount of a proteoaminoglycan or dextran sulphate to the amount of toluidine blue in said composition on said at least one surface is selected from the group of ratios consisting of: • about 100:1, such as about 90:1 to about 110:1 (surface 1); • about 140:1, such as about 135:1 to about 145:1 (surface 2); • about 165:1, such as about 160:1 to about 170:1 (surface 3); • about 180:1, such as about 175:1 to about 185:1 (surface 4); • about 200:1, such as about 190:1 to about 210:1 (surface 5); and • about 225:1, such as about 220:1 to about 230:1 (surface 6). • about 100:1, such as about 90:1 to about 110:1 (surface 1); • about 140:1, such as about 135:1 to about 145:1 (surface 2); • about 165:1, such as about 160:1 to about 170:1 (surface 3); • about 180:1, such as about 175:1 to about 185:1 (surface 4); • about 200:1, such as about 190:1 to about 210:1 (surface 5); and • about 225:1, such as about 220:1 to about 230:1 (surface 6).