Tuesday, March 10, 2009

Lead time bias

As I go through the literature on early nephrology referral, I am troubled by the possibility of lead time bias. This was a large issue in the debate surrounding the optimal time to initiate dialysis. The problem comes from measuring survival from the initiation of dialysis.

Patients with good nephrologic care regularly get started on dialysis earlier than their counterparts with poor or non-existent CKD care. This is evidenced by the lower creatinines at the time of initiation of dialysis in patients with early referral seen in multiple studies.

This is consistent with my practice where I tell my patients that we "...want to delay dialysis as long as possible, but not longer than possible..." because if they have profound malnutrition or advanced heart disease due to the delay of dialysis they will do poorly once they transition to dialysis.

Because of this skew in the initiation of dialysis it is important to account for that in any analysis of survival on dialysis. I hope this short slide show makes this clear.

Note: I do not know if lead time bias is responsible for the prolonged survival with early referral to nephrology I just know that it needs to be accounted for and most literature ignores this potential source of error.

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