25. Prognosis Index contains three adverse prognostic factors (age >40, hemoglobin <9 g/dL, temperature >38.5ºC). Subjects with zero, one, two, or all three of these adverse factors had 6-month mortality rates of 12, 14, 31, and 62 percent, respectively. Atypical hemolytic–uremic syndrome has a poor prognosis, with death rates as high as 25% and progression to end-stage renal disease in half the patients