The invention discloses diagnostic techniques based on single cell genomics, consisting of obtaining a blood sample, enriching a sub-population of cells present in the blood sample, sequestering individual cells or group of cells from the blood sample, obtaining sequencing data from the sequestered cells or group of cells, using genetic variant information to determine the provenance of the cells, and genetically analyzing the cells of the correct provenance to provide a diagnostic readout. Using the cell-based testing techniques of the invention, the number of false positives is greatly reduced when compared to cell-free DNA (cfDNA) based traditional testing techniques. The invention may be effectively employed for non-invasive prenatal (NIPT) diagnostics, oncological testing and other diagnostic procedures.