e135 Correspondence To the Editor:

We read with interest the article by Sabino et al,1 who show a dif-ference in the rate of progression to cardiomyopathy of 1.85 % per year among 499 initially asymptomatic Trypanosoma cruzi–seropositive blood donors compared with 488 T cruzi–seronegative individuals (control group). That is, in a 1-year period, of 100 patients with the indeterminate form of Chagas disease, ≈2 patients will develop some cardiac alteration that is exclusively attributable to T cruzi infection. However, the study has some limitations that should be considered in the interpretation of the results. First, because of its retrospective design, instead of having programmed repeated follow-up observa-tions on each subject, cardiac evaluation was done only once (at a single point in time), 7 to 14 years after the index blood donation. So, the approximate or exact date at which progression to cardiomyopathy occurred was not known. Because T cruzi–infected individuals who develop cardiomyopathy usually do so within 20 years after bein