Avaliação de fatores associados à soropositividade do teste ML Flow e à reatividade ao Teste de Mitsuda em contatos de casos-índice de hanseníase em um centro de referência em Minas Gerais, Brasil

Abstract

Introduction: Leprosy is an infectious disease that affects the skin and peripheral nerves and has great disabling potential. Brazil is the second country with the highest number of new cases in the world. The supervision of contacts is one of the pillars for the disease control. The evaluation of sociodemographic, epidemiological, and immunological factors may contribute to the supervision of leprosy contacts. Describing these factors in this population may add useful information to identify conditions that deserve greater attention upon the management of leprosy contacts. Objective: To evaluate the sociodemographic, epidemiological profile and its relationship with the ML Flow and Mitsuda tests of the domiciliary contacts of new leprosy cases attended at the Health Dermatology Service of the Eduardo de Menezes/Fhemig Hospital. Methods: A cross-sectional study, consisting of 131 leprosy contacts. The dependent variables were the ML Flow test and the Mitsuda test. The Mitsuda test was read after 21-28 days with a millimeter ruler and register digital dermoscopy. The area calculation was performed according to the presentation of the reaction: circle or ellipse (mm²). The software image tool 3.0 was used to calculate the area of the images obtained by dermoscopy. The ML Flow test was performed according to the protocol described by Bührer-Sékula. Results: There was an excellent correlation between the total area of the Mitsuda test and the standardized reading, according to Spearman's correlation coefficient (0.936); the positivity for ML Flow was 13.0% and the positivity of the Mitsuda test (5 mm) was 66%. The chance of obtaining a positive ML Flow result in contacts with positive Mitsuda is 72% lower than that of Mitsuda negative contacts (95% CI = 0.09-0.86). At each additional dose of BCG, it was observed a 4.23-fold increase in the chance of a positive Mitsuda test (95% CI = 1.92-9.30) and a 14.35 mm² increase in the Mitsuda test area, varying between 9.63 and 19.07 mm² (95% CI = 9.63-19.07). Income, water network, sewage, area of residence and schooling, people-domicile and number of rooms (p value> 0.05) were associated with Mitsuda test negativity. The predominance of positive Mitsuda was higher among the contacts that resided in cities with high HDI. The median HDI was higher among those with Mitsuda positive and larger areas of Mitsuda (p value <0.001). There was a significant and inverse correlation between the number of people in the household and the results of the Mitsuda test area (p value = 0.012) and the number of patients in the community, in addition to the index case (p value = 0.001). Conclusions: There is a significant correlation between the standardized reading and the total Mitsuda test area; lower expression of cellular immunity, identified by reading the Mitsuda test may contribute to ML Flow positivity; the amount of BCG scars influences the response to the Mitsuda test in leprosy contacts; there is a relationship between determinants of social vulnerability with lower cellular immunity expressed by the Mitsuda reaction. These results are evidence that surveillance of leprosy contacts involves a complex structure.