Estudo comparativo das técnicas de Ziehl-Neelsen e Auramina O nabaciloscopia do raspado dérmico de quatro e seis sítios em casos novosde hanseníase, em serviço de referência de Belo Horizonte

Abstract

Leprosy is regarded as an important public health problem worldwide. Over recent decades, the prevalence rate has declined, however the detection rate remains high. Skin smear is the best supplementary proceeding for the diagnosis and is performed by Ziehl-Neelsen´s staining method. However, there are difficulties such as the detection of bacilli in paucibacillary cases and the considerable time of reading, which can lead to fatigue and error. Fluorescence microscopy has shownpromise in the detection of alcohol-acid resistant bacilli, especially in cases of scarce bacilli. Brazilian Health Department requires collection of samples on four sites; however, some reference centers perform the procedure on six sites. Using two independent examiners on skin smear, in new cases of leprosy, descriptive and exploratory study was carried out comparing Ziehl-Neelsen and Auramine staining, among four and six sites, correlating the variables sex, age, number of skin lesions, number of nerves involved, Madrid classification and the operational classification adopted by Health Department. The study group consisted of 110subjects, who were admitted at a Reference Service in Sanitary Dermatology in the city of Belo Horizonte, Minas Gerais, Brazil, from September 2006 to October 2007. Skin smears were obtained from six sites (skin lesion, contrary elbow, ear lobes and knees), with two samples from each one to be stained by the techniques, and expressed as quantitative and qualitative results. Agreement analyses used Kappa index and Intraclass Correlation Coefficient. The association of skin smears with the variables was analyzed through logistic regression. Thestrength of the agreement was considered to be very good in the analysisinterobserver, between the techniques and the number of sites examined, according to Landis & Koch´s criteria. Although the staining methods do not differentiate when considering its clinical applicability, fluorescence microscopy detected more bacilli on bacterial index. Skin smears tended to be more positive when a greater number of sites was analyzed, but without statistical significance (p=0.50). The agreement between skin smear and operational classification was considered to be moderate and there was significant association between this procedure and Madrid classification. Positive smears observed (35%) werestatistically correlated with patients who had more than five skin lesions (Exp (B): 19,29) and more than one nerve involved (Exp(B): 3,51). Fluorescence microscopy, as well as the analysis of a greater area, either by increasing the number of sites or surface examined, can provide options to increase the sensitivity of smear in paucibacillary cases with negative results on four sites. The result of this study supports Ziehl-Neelsen on four sites as an auxiliary standard method for the diagnosis and classification of leprosy.