 Heide Tullberg-Reinert

Heide Tullberg-Reinert coauthored the 2002 study of chemical interference with the MTT assay. Washing treated cells before adding MTT reduced the direct redox interference observed with kaempferol.^[ref]

That experimental comparison connects the readout to the presence of the test substance during measurement. Washing is an intervention on assay conditions, rather than proof that the earlier exposure had no biological effect. It may remove extracellular material while leaving changes in cell viability or cellular metabolism.

In an original model, let the cellular contribution to absorbance be $0.30$ and removable chemical interference be $0.25$. Before washing the total is $0.55$. Removing 90 percent of the interference leaves $0.30+0.025=0.325$, still above the cellular contribution. A smaller signal after washing supports an interference explanation, but residual signal and loss of loosely attached cells must also be considered. Paired negative controls and independent counts make the interpretation stronger than washing alone.