The quest to develop diagnostic tests that need only a single drop of blood may be in vain. "Students in my lab are developing novel, low-cost platforms for anemia, platelet and white blood cell testing in low-resource settings, and one of my students, Meaghan Bond, noticed there was wide variation in some of the benchmark tests that she was performing on hospital-grade blood analyzers," said lead investigator Rebecca Richards-Kortum, a Rice University professor and director of the Rice 360°: Institute for Global Health Technologies. Moreover, it appears the discrepancy stems from variations in the quantity of various biomarkers found in a single drop of blood. The team used best practices when carrying out the single-drop tests, and averaging results from 6 to 9 drops of blood from the same person produced results similar to those achieved by traditional venous blood draws. So a single drop of blood may simply be too small a sample to be reliable, regardless of the technology used. That's bad news for embattled Theranos and the myriad others marketing the promise of finger-prick blood tests. Release | Study abstract