Leprosy and pregnancy : detection coeffi cient and proposal for a new index

Introduction: Our study presents a method to generate a novel detection coeffi cient for the association between leprosy and pregnancy (DCLP). Methods: The DCLP was calculated for women from the State of Pará (2007-2009), Brazil. Data were ordered, divided into fi ve equal parts (corresponding to the P20, P40, P60, and P80 percentiles), and classifi ed as low, medium, high, very high, or hyperendemic. Results: Using the new index, we established the DCLP parameters for low (<0.36), medium (0.36-0.69), high (0.70-1.09), very high (1.10-1.50), and hyperendemic (>1.50). Conclusions: The new DCLP is more appropriate than the overall detection coeffi cient (DC), which does not take into account the particularities of the interaction between a disease and a specifi c physiological state.

In clinical practice, there are several ways to study the patterns of disease occurrence in a population.Analyses of the epidemiological factors related to behavioral, environmental, immunological, nutritional, and genetic aspects are among the most important approaches.These analyses can be performed by calculating epidemiological indicators, which are important tools for evaluating disease severity 1 .Among these indicators, detection coefficients (DCs) are important evaluation parameters, as they show the magnitude of disease occurrence in a population and can be easily calculated and interpreted 2,3 .
Brazil has the second highest incidence and prevalence of leprosy, an endemic disease affecting several countries worldwide 4,5 .DCs have been widely used to measure the evolution of this disease within a population (in particular, in the general population and children under 15 years of age).However, the rate of disease occurrence in pregnant patients has not yet been assessed, and studies on DCs that specifi cally assess the association between leprosy and pregnancy are lacking 5,6 .This points to an important information gap in evaluating leprosy severity among the population of pregnant women 7 .In general, leprosy severity in pregnant patients is evaluated by the overall DC, which is calculated for the population as a whole and makes no distinction between women of fertile age and men [3][4][5][6] .
Thus, the objective of this study was to propose a new DC that assesses the association between leprosy and pregnancy, based on an epidemiological survey.
The database for this study was closed in November 2011.We established a new epidemiological index -the detection coeffi cient for the association between leprosy and pregnancy (DCLP).The DCLP was based on a study by Palacios et al 6 .and is depicted below: 0

Range of the coeffi cient Interpretation
Above 1.50 hyperendemic Depending on the population quantum, a reference of 100,000 inhabitants can also be used for analysis adequacy.Since this study was performed in the municipalities of Pará and by year, the 10,000 inhabitant constant was maintained during the study period.
To estimate the endemicity patterns of the association between leprosy and pregnancy, the DCs were fi rst calculated for all counties (143 counties in 3 years, totaling 429 coeffi cients) and sorted in increasing order (using the 'sort and fi lter' and then the 'sort smallest to largest' functions) in a single column using Microsoft Offi ce Excel 2007.Subsequently, the column containing the DCs was selected, the 'sort and fi lter' and 'fi lter' functions were applied, and repeated zero values were excluded to avoid interference in the calculation of percentiles.A total of 84 signifi cant values (positive numbers) was found.Then, the DCs corresponding to the P 20 , P 40 , P 60, and P 80 percentiles (four percentiles dividing the ordered series of coeffi cients into fi ve equal parts) were calculated.One advantage of using percentiles is that they can be applied to any set of continuous data, even if it does not show any statistical distribution 7 .
Each of the fi ve parts corresponds to a track featuring an endemic pattern of the disease according to the percentiles formula: low, medium, high, very high, and hyperendemic (Figure 1).The calculated values were: P 20 = 17 (or the 17 th term of the increasing sequence of coeffi cients), P 40 = 34 (34 th term), P 60 = 51 (51 st term), and P 80 = 68 (68 th term).In the 2007 Excel software, the 'insert' (ƒχ) followed by the 'percentile' function were selected.In the opened frame, the fi eld matrix was automatically fi lled when all rows of the DC column were selected, while the fi eld K (referring to the k th percentile of the values in the range) corresponded to each of the values found for the calculation of the P 20 , P 40 , P 60, and P 80 percentiles (17, 34, 51, and 68, respectively).K represents the percentile values within the range of 0-1 (0.17, 0.34, 0.51, and 0.68, respectively).This ultimately resulted in the values defi ning the endemicity parameters for the DCLP (Figure 1).
The percentiles we identifi ed were: P 20 = 17° or 0.36, P 40 = 34° or 0.70, P 60 = 51° or 1.10, and P 80 = 68° or 1.50.Considering these values, the scale of the parameters for the DC of the association between leprosy and pregnancy is depicted in Table 1.
The methodology chosen in our study allowed for the creation of a new index, summarized in Figure 2, providing a tool that can be used to establish a more precise epidemiological profi le of the association between leprosy and pregnancy.According to the few existing reports, an outbreak or worsening of leprosy results from the physiological changes associated with pregnancy 6,8-10 .Thus, the creation of an indicator allowing a more accurate epidemiological assessment of the association between illness and the physiological state in question is imperative.We show that the methodology adopted in this study was adequate for this purpose, and we suggest that the DCLP a new and useful tool for the evaluation of the biological interaction of leprosy with pregnancy.However, although our study is based A population-based survey with a focus on leprous pregnant women from the State of Pará, Brazil, was conducted using data from 2007 -2009.The study population consisted of 149 women, including 57 cases of pregnant women with leprosy detected in 2007, 47 in 2008, and 45 in 2009.The variables of interest for this study were collected from data available in the National Health System Electronic Databases [Departamento de Informática do Sistema Único de Saúde (DATASUS)] and the Ministry of Health/Information System for Notifi able Diseases [Sistema de Informação de Agravos de Notifi cação/Ministério da Saúde (SINAN/MS)].The population data for the women aged 12-49 years were obtained from the Brazilian Institute of Geography and Statistics [Instituto Brasileiro de Geografi a e Estatística (IBGE)].

FIGURE 1 -
FIGURE 1 -Summary of the calculation of the percentiles that correspond to the endemicity patterns of leprosy associated with pregnancy.P i : percentile value; i = 1, 2, 3, ..... 99 (or a percentile estimate of 20, 40, 60, and 80 in this study); N: number of observations (N = 84 in this survey); DCLP: detection coeffi cient for the association between leprosy and pregnancy.