Hydrophilic threads as platforms for inexpensive, low volume, portable diagnostic systems, and methods of making the same are described. A diagnostic system includes a hydrophilic loading thread having an inlet zone at a proximal end; a testing zone at a distal end; and an intermediate zone located between the inlet zone and the testing zone, wherein the testing zone does not directly contact the inlet zone. In another aspect, a diagnostic system includes (i) a hydrophilic loading thread that includes an inlet zone at a proximal end and an intermediate zone at a distal end; and (ii) one or more additional hydrophilic threads that contact the intermediate zone of the loading thread. A method of detecting the presence or absence of an analyte in a fluid sample includes applying the sample to an inlet zone of a diagnostic system that includes a hydrophilic loading thread with an inlet zone at a proximal end; an intermediate zone; and a testing zone at a distal end; wherein the testing zone does not directly contact the inlet zone.