Kaplan-Meier analysis of the probability of survival with age for GATA-1^low (squares) and W/W^v(triangles) mice.

For the GATA-1^low mice, the probability of survival was calculated starting with 178 mutants born in the facility over a period of 3 years. Because the birth of the animals was not synchronous and animals were killed for experimental purposes, the number of mice used to calculate the survival curve changed with age and included a total of 147 animals up to 13 months and 31 animals from 14 months on. In the case of the W/W^v mice, the survival probability was calculated on a cohort of 204 mice, 50 of which were censored because they were killed for other experiments. The 2 survival curves are statistically different (P < .001) by Mann-Whitney rank sum test.