PARASITOLOGICAL METHODS FOR THE DIAGNOSIS OF CHAGAS’ DISEASE
(adapted from WHO 1991:38)
| Methods | Type of laboratorya | Percentage of Sensitivityb | |
| Acute stage | Chronic Stage | ||
| DIRECT | |||
| Thin Smear | A/B | >60 | <10 |
| Thick blood smear | A/B | >70 | <10 |
| Fresh blood examination | A/B | 80‑90 | <10 |
| Strout | A/B | 90‑100 | <10 |
| Buffy coat on slide | A/B | 90‑100 | <10 |
| INDIRECT | |||
| Xenodiagnosis | B | 20‑50 | |
| Blood cultures | B | 40‑50 |
aA: Health center laboratories located in areas at risk ofvectorial and nonvectorial transmission (the infrastructure is that from the first level of medical care upwards). B: Specialized laboratories for parasitological diagnosis. A and B laboratories are found at MSSP and IBBA in La Paz, MSSP in Cochabamba, and MSSP in Santa Cruz. Since 1991 USAID has helped improve these laboratories for chagas diagnosis. Sucre lacks an adequately equipped B laboratory.
bAs compared to xenodiagnosis for the acute stage of the infection and to serological diagnosis for the chronic stage.
Relatively few Latin Americans are tested for T. cruzi due to a combination of factors including cost, pain, and a fatalistic attitude that, if they test positive, medications are prohibitively priced and only partially effective, with the probability that they will be again be parasitized. There is also the social cost of being ostracized, although this is less true in Bolivia than in some other places. Epidemic diseases frequently lead to old and new prejudices surfacing that lead to ostracism of the victims (see Foege 1988, and Lederberg 1988, in regard to AIDS in the United States). It would not be a very popular decision for immigrants to the United States to let others know they are seropositive for T. cruzi.
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