Abstract: A solution is described for preserving cells and/or extra-cellular components in naturally expressed bodily fluids (e.g. saliva, sputum, urine) for further downstream analysis and/or for diagnosis of a medical condition. The solution may be hypertonic with respect to blood. Techniques are described for enriching cells from a sample of a naturally expressed bodily fluid, and/or for analysis, e.g. to diagnose medical conditions such as cancer, obesity, infections, autism, Alzheimer disease, hetotological disorders, cardiovascular disease or disorders, diabetes, vulnerable plack, LTBI, HIV infection, COPD, ACQS.