considered associated should be flanked by markers showing at least moderate association to the phenotype under study. Interestingly, imputed markers showing high concordance to empiric ones (for the derived association statistic) presented significantly higher total sum of association statistics as compared to false-positive markers. Indeed, the same procedure was applied to the complete set of imputed markers considered associated (10 -5) in the WTCCC hypertension dataset with similar results (Additional file 8, Figure S4). The complex nature of WTCCC databases impose a barrier for the interpretation of results in this manuscript and could be considered a major source of the bias especially in imputed markers. This barrier originates from the fact that control and cases were not ideally matched in terms of their ancestry and it is expected that some association statistics derived from directly genotyped markers and especially from imputed markers are, indeed, susceptible to an increased odds of both type-I and type-II errors. Nevertheless, our results are concordant with the idea that additional information can be gathered from nearby markers in order to prioritize potentially associated markers for follow-up studies.
