Mixed Race Studies

Reliability of race assessment based on the race of the ascendants: a cross-sectional study

BMC Public Health
Volume 2, Number 1 (2002-01-16)
DOI: 10.1186/1471-2458-2-1
5 pages

Sandra C. Fuchs
Department of Social Medicine, School of Medicine
Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil

Sylvia M. Guimarães
Department of Internal Medicine, School of Medicine
Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil

Cristine Sortica
School of Medicine
Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil

Fernanda Wainberg
School of Medicine
Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil

Karine O. Dias
School of Medicine
Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil

Mariana Ughini
School of Medicine
Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil

José Augusto S. Castro
Department of Internal Medicine, School of Medicine
Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil

Flavio D. Fuchs
Department of Internal Medicine, School of Medicine
Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil

Race is commonly described in epidemiological surveys based on phenotypic characteristics. Training of interviewers to identify race is time-consuming and self identification of race might be difficult to interpret. The aim of this study was to determine the agreement between race definition based on the number of ascendants with black skin colour, with the self-assessment and observer’s assessment of the skin colour.

…Methods

A cross-sectional study was conducted on a sample of 50 women aged 14 years or older, which were systematically selected from an outpatient clinics of a University affiliated hospital in Porto Alegre, southern Brazil. Participants included in the study answered to a pre-tested and structured questionnaire, which collected information on the number of black ascendants (parents and grandparents), school attendance, and included a self-assignment of the colour of skin as well as the observer assessment of skin colour.
 
In a preliminary phase, a training was provided to the observers to standardise the identification of the skin colour and in the details of several phenotypic characteristics employed in Brazil before [10] such as the colour of hair, lines and hands’ palm surface. Following the training, the principal investigator and the research assistants observed 28 women and compared their findings of the physical features. The research team reached full agreement for skin colour (white, mixture or black), hair colour (blonde, light brown, medium brown, dark brown or black), lines and hands’ palm surface (pink palm and colourless lines, pink palm and red lines or white palm and dark lines) for the last 15 women observed. We also investigated the race of ascendants, through the question: “Which are the race of your ascendants: parents and grandparents?”. A total of six research assistants were certified for the study.
 
During the study, after the informed consent was obtained, one interviewer applied the questionnaire asking questions to the participants and the research team independently registered the information on physical characteristics, observing the women under sunlight. All interviewers were blinded to each other answers. Skin colour was described by the observers as white, mixed or black, the self-assigned skin colour used white, black, mixed, and local words meaning light mulatto and dark mulatto. The race of the parents and grandparents was investigate using a heredogram, which incorporated two generations to the assess the inheritance. Even though information could be reported for a maximum of six ascendants some women did not know the father or grandparents. Therefore, we collapsed the categories with more than 3 ascendants of black origin in the category of at least three black ascendants. There was investigated a sample of 50 women, which did not include the 28 women at the training phase. This sample size was sufficient to detect an agreement of at least 85%, with an error of 10%, and a confidence interval of 95%. In order to calculate the kappa coefficients, self-reported mixed skin colour was collapsed with light mulatto and dark mulatto. Analysis were carried out through Chi-square for contingency tables and kappa statistics to calculate to what extent the observers agreed beyond what we would expect by chance alone [15]. Kappa coefficients were calculated from observation of six interviewers and the skin colour self-assigned by the participant. The Kappa statistic was calculated for each two categories (white vs. non white; black vs. non black and mixed vs. non mixed) and a global Kappa with 95% confidence interval for all three categories. Kappa greater than 0.75 was taken as an excellent agreement, between 0.75 and 0.40 intermediate to good agreement, and below 0.40, poor agreement. The reliability of self-assigned black, mixed, or white skin colour with the number of black ascendants was obtained by weighted kappa. Weights were giving to the frequencies in each cell of the table according to their distance from the diagonal that indicates agreement [16]. The study was approved by the Ethics Committee of our Institution and all participants gave their informed consent to participate…

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