MRD Detection and Quantification by HTS results interpretation problem


Use TCR/BCR HTS in MRD detection is no longer a new concept. As they (many articles) often say, “The MRD Test by HTS, however, has been shown to detect MRD at levels as low as 0.0001% (1 cancer cell per 1 million white blood cells).”

But how do they calculate how many cancer cells are there in the total WBC? Set BCR seq for B-ALL as an example, the final result only can tell how many identical sequence reads are there in total sequence reads in the pool. But the pool should be total B cells because the library we prepared for sequencing is BCR libraries not total WBC libraries. If you don’t use flowcytometery to identify the percentage of B cells in the WBC first, just based on the seq data, I don’t think you can claim as “1 cancer cell per 1 million white blood cells)”. U only can say 1 cancer cell per 1 million B CELLS. Right?
Or there have some other ways I didn’t think about?