A Positive Chagas Screen From a Blood Donation, 15 Years After Bolivia
A blood donation deferral letter is how D.M. learned he has Chagas disease, fifteen years after leaving rural Bolivia. His echocardiogram is normal — chronic indeterminate phase, no cardiomyopathy. The one major trial of antitrypanosomal treatment found no cardiac benefit, but it studied patients who already had heart disease. Whether that result applies to him at all is the actual question.
D.M., a 45-year-old man, spent fifteen years running an agricultural cooperative with a small missionary organization in rural Bolivia before moving back to the United States three years ago to be closer to his aging parents. He found out he had Chagas disease the way a meaningful share of people in this country actually do — not from any symptom, but from a deferral letter after donating blood for the first time since he'd returned, informing him his sample had screened positive for Trypanosoma cruzi antibodies and that he was permanently barred from donating again. He didn't know what to make of the letter and sat on it for several months before a friend, a nurse, told him it was worth actually seeing someone about.
His workup since has been reassuringly unremarkable in every way except the one that matters: a confirmatory second serologic test, an ECG, and an echocardiogram all came back showing no evidence of the cardiomyopathy or conduction abnormalities that define progression beyond this disease's earliest chronic stage. He is, in the language of Chagas staging, in the indeterminate phase — infected, seropositive, and structurally normal. This is exactly where the field's own best evidence gets genuinely thin. The BENEFIT trial, the largest randomized study of antitrypanosomal treatment in chronic Chagas disease, found that benznidazole reduced parasitemia and serologic titers substantially but did not reduce cardiac events over five years of follow-up — a real, disappointing result that reshaped how the field talks about treating this disease. But BENEFIT enrolled patients who already had established cardiomyopathy. It never actually tested whether treating someone at D.M.'s stage, before any organ damage exists, changes his odds of ever developing it. Most current guidance still recommends treatment for patients under fifty in the indeterminate phase — he is 45, just inside that window — but the honest reason is inference from an earlier disease stage a negative trial didn't study, not new positive evidence that it works there.
A trial that answered a different patient's question
I'd treat him now, with benznidazole. BENEFIT is a real, important negative trial, but it studied patients who already had established cardiomyopathy — it never tested whether treatment changes the odds of getting there in the first place for someone at D.M.'s stage. Most current guidance still recommends treatment under fifty in the indeterminate phase, and he's 45. That window narrows substantially as patients age past it.
I'm not claiming there's positive trial evidence proving benefit at his stage — there isn't. I'm arguing BENEFIT's negative result doesn't disprove it either, because it never asked his question.
I'd actually read BENEFIT the opposite direction. It achieved real, substantial parasitological and serological improvement and still failed to show any cardiac benefit — that's exactly the kind of surrogate-endpoint disconnect that should make us skeptical treatment will prevent cardiomyopathy either, a claim no trial has directly tested in a patient at his stage.
The age-window argument is really an argument from guideline momentum, not new evidence. And benznidazole isn't free of cost — peripheral neuropathy and rash lead to real discontinuation rates in actual trial populations. I don't think we should be prescribing it on inference alone.
I think you're both right about your own piece of this, and that's actually the point — this is genuine equipoise, not a settled question either of you is failing to see clearly. I'd rather have an honest conversation with him naming that gap directly than hand him a guideline recommendation as if it were proven benefit.
If he decides to treat, I'd start with benznidazole over nifurtimox specifically — better-characterized tolerability and far more accumulated clinical experience, with nifurtimox held in reserve for intolerance. But which drug isn't really today's hardest question. Do I treat at all is, and that one belongs to him as much as to us.
Agreed: no treatment decision was made today. D.M. left with a genuinely honest account of what is and isn't known — that BENEFIT's negative result concerns a later disease stage than his own, that no trial has directly tested benefit at his stage, and that both treating and not treating are defensible choices supported by different reasonable readings of the same evidence gap — along with a plan for annual cardiac surveillance regardless of what he ultimately decides.
Not agreed, and explicitly not smoothed into a single recommendation: the infectious disease physician would still counsel toward treatment given his age and the narrowing guideline window; the clinical pharmacologist would still counsel toward observation given the surrogate-endpoint concern. Neither view was presented to D.M. as more authoritative than the other — both were given to him directly, in roughly those terms, so the actual decision could be his rather than whichever specialist happened to speak last.