We've published work in Analytical Chemistry on a serum-based blood test for lung cancer that reads the full Raman spectrum of a patient's blood rather than chasing a single biomarker. The appeal of this "data-first" approach is that it needs no predetermined target and only 5 microliters of serum, but is limited by the high similarity in chemical composition between healthy and cancer serum, which leaves the disease-relevant differences buried in noise and in the natural biological variation from one patient to the next.