Applying the triads method in the validation of dietary intake using biomarkers.

The triads method is applied in validation studies of dietary intake to evaluate the correlation between three measurements (food frequency questionnaire, reference method and biomarker) and the true intake using validity coefficients (Á). The main advantage of this technique is the inclusion of the biomarker, which presents independent errors compared with those of the traditional methods. The method assumes the linearity between the three measurements and the true intake and independence between the three measurement errors. Limitations of this technique include the occurrence of ρ > 1, known as "Heywood case", and the existence of negative correlations, which do not allow the calculation of Á. The objective of this review is to present the concept of the method, describe its application and examine the validation studies of dietary intake that use the triads method. We also conceptualize the "bootstrap" method, used to estimate the confidence intervals of the validity coefficients.

Applying the triads method in the validation of dietary intake using biomarkers / Método das tríades na validação do consumo alimentar com biomarcadores

The triads method is applied in validation studies of dietary intake to evaluate the correlation between three measurements (food frequency questionnaire, reference method and biomarker) and the true intake using validity coefficients (Á). The main advantage of this technique is the inclusion of the biomarker, which presents independent errors compared with those of the traditional methods. The method assumes the linearity between the three measurements and the true intake and independence between the three measurement errors. Limitations of this technique include the occurrence of Á > 1, known as "Heywood case", and the existence of negative correlations, which do not allow the calculation of Á. The objective of this review is to present the concept of the method, describe its application and examine the validation studies of dietary intake that use the triads method. We also conceptualize the "bootstrap" method, used to estimate the confidence intervals of the validity coefficients.

O método das tríades vem sendo utilizado em estudos de validação do consumo alimentar para avaliação da correlação entre três variáveis (questionário de freqüência alimentar, método de referência e biomarcador) e a ingestão real, por meio dos coeficientes de validade (Á). A principal vantagem deste método é a inclusão do biomarcador, que apresenta erros independentes dos métodos tradicionais. Os pressupostos desta técnica são a linearidade entre as três variáveis e a ingestão real, e a existência de erros independentes entre as variáveis. Entre as limitações deste método, destaca-se a existência de Á > 1, conhecido como "Heywood case", e de correlações negativas, que não permitem o cálculo do Á. O objetivo deste trabalho foi apresentar o conceito do método, descrever a sua aplicação e examinar estudos de validação do consumo alimentar que utilizaram o método das tríades, além de conceituar o método "bootstrap" para obtenção de intervalos de confiança dos coeficientes de validade.