RESUMEN
This study was undertaken to assess whether the immunoperoxidase technique using anti-BCG serum is able to confirm the diagnosis of early leprosy among patients whose unique clinical manifestation is a localized area of sensory loss, in a higher proportion than the routine mycobacterial staining methods, namely hematoxylin-eosin and Wade. The study was held in the north of a hyper-endemic area of leprosy, Manaus, Amazonas (Brazil). Fifty-one paraffin-embedded skin biopsy blocks were retrieved and processed for the immunohistochemical study, by means of anti-BCG polyclonal antibodies for the detection of mycobacterial antigens. The routine stains confirmed the leprosy diagnosis in 17% of the cases, while the immunostaining method confirmed it in 47%. The McNemar test showed that the observed difference between these two techniques was statistically significant (p = < 0.05). In the same way, 50 blocks of skin conditions considered in the differential histopathological diagnosis of early leprosy were processed for the immunohistochemical test to analyze the possibility of false-positive results which occurred in 8 (16%) patients. The study suggests that immunostaining may increase the proportion of the routine histological diagnosis of leprosy in patients who have sensory loss only, even while using biopsies obtained in fieldwork conditions. This is very advantageous in hyper-endemic areas and in areas that are in the post-elimination period of leprosy control where sensory loss may be a sentinel sign of the disease.