A method for screening a subject for determining whether any or all of the following organ systems: the gastrointestinal system, the respiratory system, and the central nervous system, has a pathology, which method comprises: a. measuring levels of miRNAs which are enriched in the gastrointestinal system, miRNAs which are enriched in the respiratory system, and miRNAs which are enriched in the central nervous system, in a bodily fluid sample collected from the subject; b. measuring levels of normalizer miRNAs in the same bodily fluid sample collected from the subject; c. calculating the ratios of the levels of the miRNAs measured in steps (a) and (b); d. comparing the ratios of the levels of the miRNAs calculated in step (c) with the corresponding control ratios, and e. (i) identifying the subject as being afflicted with a pathology of a particular organ system when the ratios of the levels of the miRNAs enriched in said organ system to their respective miRNA nonnalizers, calculated in step (c), are higher than the corresponding control ratios or (ii) identifying the subject as not being afflicted with a pathology of said organ system when the ratios of the levels of the miRNAs enriched in said organ system to their respective miRNA nonnalizers, calculated in step (c), are not higher than the corresponding control ratios, wherein the miRNAs enriched in the GI system measured in step (a) comprise miR-215, miR-203, miR-192, or miR-194, and the normalizer miRNAs of step (b) comprise miR-30e-3p, miR-145 or miR-148a; the miRNAs enriched in the respiratory system measured in step (a) comprise miR-486-5p, miR-34b, or miR-192, and the normalizer miRNAs of step (b) comprise miR-142-5p, miR-146b-5p, miR-155, miR-223, miR-409-3p; and the miRNAs enriched in the central nervous system measured in step (a) comprise miR-128, miR-132, or miR-874, and the normalizer miRNAs of step (b) comprise miR-9, miR-181a, miR-491-5p, miR-141, or the miRNAs enriched in the central nervous system measured in step (a) comprise miR-134, miR-323-3p, or miR-382, and the normalizer miRNAs of step (b) comprise mir-127 or miR-370. a. measuring levels of miRNAs which are enriched in the gastrointestinal system, miRNAs which are enriched in the respiratory system, and miRNAs which are enriched in the central nervous system, in a bodily fluid sample collected from the subject; b. measuring levels of normalizer miRNAs in the same bodily fluid sample collected from the subject; c. calculating the ratios of the levels of the miRNAs measured in steps (a) and (b); d. comparing the ratios of the levels of the miRNAs calculated in step (c) with the corresponding control ratios, and e. (i) identifying the subject as being afflicted with a pathology of a particular organ system when the ratios of the levels of the miRNAs enriched in said organ system to their respective miRNA nonnalizers, calculated in step (c), are higher than the corresponding control ratios or (ii) identifying the subject as not being afflicted with a pathology of said organ system when the ratios of the levels of the miRNAs enriched in said organ system to their respective miRNA nonnalizers, calculated in step (c), are not higher than the corresponding control ratios, wherein the miRNAs enriched in the GI system measured in step (a) comprise miR-215, miR-203, miR-192, or miR-194, and the normalizer miRNAs of step (b) comprise miR-30e-3p, miR-145 or miR-148a;