Tuesday, 12 January 2016

Estimating number of MS

Clamon AB, Pereira F, Marin B, Preux PM, Alvarenga RP. Prevalence of Multiple Sclerosis in the City of Volta Redonda - Rio De Janeiro, Brazil Using the Capture-Recapture Method. Neuroepidemiology. 2016 Jan 6;46(2):88-95. [Epub ahead of print]

BACKGROUND:Multiple sclerosis (MS) prevalence in Latin America was estimated in some regions and it was found to range from 0.75 to 30/100,000. The reasons for variation in rates of prevalence around the world still are not clear, but there are environmental and genetic explanations to this phenomenon. This study aimed at estimating the MS prevalence in Volta Redonda, Brazil.
METHOD: Three sources of cases ascertainment were used and the method of capture-recapture was applied for assessing the corrected prevalence in the city of Volta Redonda in November 2012. The capture-recapture method uses data from incomplete lists and allows calculating the number of unregistered cases. Data were analyzed using a log-linear model.
RESULTS: A total of 40 MS cases was found by withdrawing overlaps of sources and it was estimated that a total number of 40 cases (95% CI 13.5-118.8) were not detected by the sources. The corrected prevalence of MS was, then, 30.7/100,000.
CONCLUSION: Our study was the first in Brazil to use the capture-recapture method to assess the prevalence of MS, demonstrating the highest prevalence rate so far. It is necessary to perform other similar studies and in other regions of the country using the same method for a better evaluation of the true prevalence of MS our country.

Mark and recapture is a method commonly used in ecology to estimate an animal population's size. A portion of the population is captured, marked, and released. Later, another portion is captured and the number of marked individuals within the sample is counted. Since the number of marked individuals within the second sample should be proportional to the number of marked individuals in the whole population, an estimate of the total population size can be obtained by dividing the number of marked individuals by the proportion of marked individuals in the second sample. The method is most useful when it is not practical to count all the individuals in the population. So something similar was used in Brazil to assess the number of  people with MS.

2 comments:

  1. The last paragraph is copied from Wikipedia verbatim.

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  2. The numbers of cases in Brazil has increased in the last 20 years is well known ... Perhaps the strong miscegenation of the population, allowing genetic changes, as well as infections undetected EBV and low Vitamin D rate not related to the lack of sun exposure?! Who knows...We need to invest in scientific research, only those who have not realized this was the Ministry of Health the Brazilian Government ...

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