We agree that survivor bias, sometimes referred to as survival of the fittest, is a possible problem in an observational study of the association between initial eGFR at dialysis initiation and survival. As suggested by Dr Pickering, survivor bias might be reduced by calculating survival time from a common eGFR starting point rather than from the time of initiation of dialysis, but this is not possible given that many patients initiate dialysis before researching the “common” eGFR point.
Rosansky SJ, Eggers P, Jackson K, Glassock R, Clark WF. Survivor Bias in Early- vs Late-Start Hemodialysis Studies—Reply. Arch Intern Med. 2011;171(5):477-478. doi:10.1001/archinternmed.2011.66