[Combined use of serologic markers and spatial analysis for epidemiological surveillance of leprosy Uso conjunto de los marcadores serológicos y del análisis espacial en la vigilancia epidemiológica de la lepra].
Objective: To evaluate the combined use of serologic markers and spatial analysis to increase the sensitivity of leprosy epidemiological surveillance.
Method: This cross-sectional study was performed with neighbors of leprosy cases and neighbors and family members of schoolchildren with a positive anti-phenolic glycolipid I (PGL-I) test in Diamantina, state of Minas Gerais, Brazil. Neighbors were those living within a 100-m radius of schoolchildren or leprosy cases. Data collection included a semi-structured interview, dermatologic examination, and rapid ML Flow test. All residential addresses were georeferenced. Multivariate regression and spatial analysis were performed with anti-PGL-I seropositivity as the dependent variable.
Results: The study included 1 491 individuals: 1 009 (67.7%) family members and neighbors of schoolchildren with positive serology test and 482 (32.3%) neighbors of leprosy cases. Of the total, 421 (28.2%) were positive for anti-PGL-I. Seropositivity was higher among family members and neighbors of seropositive schoolers ( < 0.001), among people with family income of 1 minimum wage ( < 0.001), among the youngest participants ( < 0.001), and among those living in homes with one to five rooms ( = 0.007). The seropositivity rate was higher in the geographic area corresponding to seropositive schoolchildren ( < 0.001), that is, the spot with the highest number of cases was different from the spot with the highest rate of seropositivity.
Conclusions: The combined use of serologic markers and spatial analysis allowed us to easily identify operational weaknesses of services and a possible occult leprosy endemism in the municipality's urban census tracts. Tracing of social contact and neighbors, active search, educational campaigns, school surveys, and territorial analyses facilitate the early diagnosis of leprosy.