Modular point-of-care devices, systems, and uses thereof

A method of detecting at least two analytes present at different concentrations in a small-volume biological sample, the method comprising:

• providing a cartridge comprising a housing carrying i) a sample collection unit containing ii) a biological sample having a volume of no more than about 500 microliters (μL), iii) an array of individual, addressable reagent units, and iv) an array of individual, addressable assay units, wherein each of said addressable reagent units is addressed to correspond to an addressable assay unit, and wherein said reagent units and said assay units provide all the reagents and assay units required for analyzing said biological sample for the presence of said at least two analytes;
• positioning said cartridge in a benchtop instrument effective that a fluid transfer device in said benchtop instrument may transfer at least a portion of said biological sample from said sample collection unit;
• transferring at least a portion of said biological sample from said sample collection unit to an individual assay unit to provide a first sample portion and at least a second sample portion, wherein said second sample portion is not in fluid communication with said first sample portion;
• diluting, by at least about 10-fold, at least one of said first sample portion or said second sample portion effective that signals produced by assays indicative of said at least two analytes are within detectable ranges;
• performing a first assay for detecting the presence of a first analyte in said first portion of the biological sample;
• performing a second assay for detecting the presence of a second analyte in said second portion of the biological sample;
• detecting a signal indicative of the presence of said first analyte;
• detecting a signal indicative of the presence of said second analyte;
• whereby the presence of each of said at least two analytes is detected in said small-volume biological sample.