A comment on “A method to measure the duration of DNA synthesis and the potential doubling time from a single sample”

Recently a method was introduced by Begg et al. (Cytometry 6:620–626, 1985) for the calculation of the DNA synthesis time, T S using flow cytometry to monitor the progression of cells that have been pulse‐labeled by bromodeoxyuridine (BrdUrd). Ideally, the method uses only a single two‐parameter histogram of the progressed cells to obtain T S . The essence of the method is to be able to obtain an initial point from general principles, draw a line through it and the measured point, and extrapolate to a level of progression that would be attained when the time is equal to T S . In this comment, explicit values are derived for the initial point and the progression of cells based on kinetic arguments, and a new method is presented for estimating T S . This new method is compared to earlier methods, and the effects of a finite labeling time and variation in the transit times are considered. Finally, an equation is developed for estimating T S following multiple measurements.