Sensitivity analysis for unmeasured confounders using an electronic spreadsheet

Abstract

Análise de sensibilidade para um confundidor não mensurado utilizando planilha eletrônica ABSTRACTIn studies assessing the effects of a given exposure variable and a specifi c outcome of interest, confusion may arise from the mistaken impression that the exposure variable is producing the outcome of interest, when in fact the observed effect is due to an existing confounder. However, quantitative techniques are rarely used to determine the potential infl uence of unmeasured confounders. Sensitivity analysis is a statistical technique that allows to quantitatively measuring the impact of an unmeasured confounding variable on the association of interest that is being assessed. The purpose of this study was to make it feasible to apply two sensitivity analysis methods available in the literature, developed by Rosenbaum and Greenland, using an electronic spreadsheet. Thus, it can be easier for researchers to include this quantitative tool in the set of procedures that have been commonly used in the stage of result validation. KEYWORDS RESUMOEm estudos que avaliam o efeito de uma dada variável de exposição e um determinado desfecho de interesse, uma situação de confusão pode ser caracterizada pela falsa aparência de que a variável de exposição produz o desfecho de interesse quando, de fato, o efeito observado se deve a um fator de confundimento que está presente. Entretanto, é pouco freqüente a utilização de técnicas quantitativas para determinar a infl uência potencial de confundidores não mensurados. A análise de sensibilidade é uma técnica estatística que permite uma medida quantitativa do impacto de uma variável confundidora não mensurada na associação de interesse que está sendo avaliada. O objetivo do artigo foi viabilizar a aplicação, por meio de planilha eletrônica, de dois métodos de análise de sensibilidade disponíveis na literatura, desenvolvidos por Rosenbaum e Greenland. Dessa forma, é possível facilitar ao pesquisador a incorporação desse ferramental quantitativo ao conjunto de procedimentos que já são comuns na etapa de validação dos resultados. DESCRITORES: Interpretação estatística de dados. Análise de sensibilidade. Fatores de confusão (Epidemiologia). Estudos observacionais.

A comparative analysis of major clinical outcomes using drug‐eluting stents versus bare‐metal stents in a large consecutive patient cohort

“…Multivariate Cox regression analysis was performed with stent type, propensity score, and any unbalanced variables as covariates. One‐way sensitivity analysis was performed to assess the possible effect of an unknown confounder [9].…”

External Adjustment Sensitivity Analysis for Unmeasured Confounding: An Application to Coronary Stent Outcomes, Pennsylvania 2004–2008

“…We implemented this analysis in an Excel spreadsheet (see Supplementary Table A1 and A5) following Greenland () and Rothman, Greenland, and Lash (), pp. 348–351,), although other approaches exist (Cabral and Luiz ; Lash, Fox, and Fin ; Luiz and Cabral ). Based on the observed associations, we used event rates of 16 and 20 percent for DES and BMS recipients, respectively, and assumed a single, binary hypothetical confounder with prevalence of 0.4 among BMS recipients…”

Sensitivity analysis for an unmeasured confounder: a review of two independent methods

“…These results can be obtained by formulas given in the work by Greenland 2 or Greenland et al 10 , and easily implemented in a spreadsheet 25 .…”

“…By establishing Γ = 1.0; 1.5; 1.8; 1.9; 2.0 and 3.0, the p-values of the upper and lower limits obtained through the Rosenbaum method are given in Table 5. These calculations are not easy to obtain manually, but they can be promptly executed using an electronic spreadsheet, as can be found in the study carried out by Cabral and Luiz 25 . The lowest value for Γ to remove all statistical significance from Mantel-Haenszel is Γ = 1.9, at a 95% confidence level.…”