Lv. Kirchhoff et al., COMPARISON OF PCR AND MICROSCOPIC METHODS FOR DETECTING TRYPANOSOMA-CRUZI, Journal of clinical microbiology, 34(5), 1996, pp. 1171-1175
The diagnosis of acute infection with Trypanosoma cruzi, the protozoan
parasite that causes Chagas' disease, is generally made by detecting
parasites by microscopic examination of fresh blood, Although highly s
pecific, this approach often lacks sensitivity, Several years ago, PCR
assays for the detection of T. cruzi were described, but the sensitiv
ities and specificities of these tests have not yet been defined preci
sely. In the present study, we first compared the sensitivities of PCR
methods that differ in sample processing as well as in the target seq
uences that are amplified. Then, we challenged eight mice with T. cruz
i, and on 31 days over a 380-day period, we compared the ability of th
e PCR method with the highest sensitivity to detect parasites in blood
with that oil microscopic examination. During the acute phase of the
infections, parasites were detected on average 3.9 days earlier by the
PCR method than by microscopy. Furthermore, the infected mice were co
nsistently positive by the PCR method during the chronic phase, while
parasites were intermittently detected by microscopic examination duri
ng that period. Overall, among the 248 comparisons, in 84 the PCR meth
od was positive and no parasites were seen by microscopic examination,
whereas the reverse was true in only 1 case, a difference that is hig
hly significant, These findings suggest that this approach should be u
sed in patients suspected of having acute Chagas' disease. Moreover, t
he higher sensitivity of the PCR method observed in both the acute and
chronic phases of the T. cruzi infections in the mice that we studied
indicates that this approach should be useful in evaluating experimen
tal drugs in T. cruzi-infected laboratory animals.